2.1. RATIONAL FARM MANAGEMENT

Farming should start from the production planning and organising of agricultural land territory. One should seek to have constant, well-considered and long-termed field order. Farm plan should be drawn, in which land use, roads and ditches are designated. Farmers should often use the farm plans. Crop rotation fields, farmstead, current and planned vegetation buffer zones should also be indicated on the farm plan. The buffer zones should separate dwelling part of farmstead from production part. It is not only element of the surrounding environment, but also element of fire-prevention system (Fig. 2.1).

Fig. 2.1. Land use and crop rotation fields in a farm plan: I – second year perennial grasses; II – winter crops; III – row crops; IV – spring crops; V – spring crops with underseeding; VI – first year perennial grasses

Planning of pasture and perennial grasses for haymaking is important. Cultivated fields should be sufficiently large, as much as possible, equal in size and of quadrangular form in order to make the use of agricultural machinery more convenient.

2.1
Sustainable agriculture should be promoted in Lithuania. It is especially important that farms with more than 15 ha of arable land would work out plans for commodity farming, fertilisation and crop-rotation, calculate nutrient (NPK) balance for the individual fields as well as for the farm as a whole.

HELCOM 1992 February 6, Recomendation 13/9. Reduction of nitrogen, mainly nitrate, leaching from agricultural land.

As much as it is possible under local conditions, the borders of fields should be associated with existing natural borders (ditches, roads, and rivulets). It is desirable that arable land would be contiguous to other types of lands: forests, meadows and pastures, swamps and water bodies. National Land Management Institute and Lithuanian Agricultural Advisory Service construct farm plans and designs rotation fields.
The choice of desired plantation structure is the very first step in the land use planning. When selecting farm type (specialisation), local conditions have to be considered – soil, relief, climate and specialisation favourable for corresponding region. In the Western zone, Eastern hilly zone and southeastern Lithuania there should be paid more attention to diary and meat husbandry and in the Middle zone to more intensive marketable plant production and its combination with husbandry. In addition, orientation of farm production should not cause any environmental problems.
When considering which crops to grow, one should think if it is possible to sell the grown products. Analysis of agricultural production processors and users demand, cost and volume of production, possibilities of transportation and cooperation are also important when selecting specialisation.
The following information is needed for planning of farming activities:

1. Prices and possibilities to sell the produced agricultural products or services.
2. Expected manufacturing expenditure of the products that will be produced for sale.
3. Correspondence of soil, climate, and infrastructure conditions to the conditions of other farms having similar conditions; analysis of advantages and disadvantages.
4. Experience and knowledge of the farmer and other persons involved about the branch of specialisation and possibilities to gain the appropriate knowledge in a short time.
5. Existing production means and circulating capital, possibilities to acquire them and to receive credits.
6. Assessment of possible environmental impact, technical-economic analysis of possibilities to use protective, precautionary and compensatory measures.

2.2

When making the commodity production plans, a land user has to take into consideration the national requirements for agricultural production in discrete regions, the territorial planning and particular land use conditions.

Resolution of the Government of the LR 1995 12 29 No. 1640 on partial alteration of LRVN 1992 05 12 resolution No.343 "On approval of special conditions of forest and land use".

Soil texture is taken into consideration for choice of plant production and crop. In light soils grains usually make the biggest part of production, potatoes and some grasses yield is good as well. Not only cereals grow better in heavier soils, but also flax, sugar and fodder beets, perennial grasses.
The plant production determines branch of animal production. Cattle need pasture while pig production may be developed where cereals are dominating. Sheep breeding is profitable in hilly regions, because there is a possibility to have dry pastures.
The area under cultivation needed for fodder is determined by the formula:

P = R/D,

P – favourable area under cultivation, ha;
R – amount of fodder needed, fodder units;
D – yield, fodder units per ha.

The plants for forage should be foreseen when calculating area under cultivation. Spring crops comprise bigger part than winter crops in heavier soils and in lighter soils - on the contrary. Under our climatic conditions the most guaranteed harvest of green fodder is received from areas of perennial grasses. In fertile sandy loam and light loam soils maize yield a good harvest. If maize is harvested at wax ripeness stage, well-chopped and fermented then valuable fodder – grain silage is obtained. This fodder allows reducing the amount of expensive fodder-concentrates in cattle ration. If there is a need for more albuminous fodder, leguminous crop or their mixture with cereals (vetch and oat, pea and barley) should be sown on to about one third of the area of the spring crop assigned for fodder.
When making a crop structure, one should think if there is a possibility to carry out all the work in time. Table 2.1 shows amount of working hours per ha needed to grow some of the crops.

Table 2.1. Work input for growing some of the crops (hours/ha)

	Soil cultivation and fertilization	Sowing and care	Harvesting	Total
Winter wheat	6-12	8-9	13-18	27-39
Barley	6-7	8	8-13	22-28
Potatoes	25-40	22-27	228-230	275-297
Sugar beets	17-28	8-12	65-75	90-115
Fodder beets	17-28	8-10	105-212	130-250
Maize for silage	12-15	3-5	7-10	22-30

Productivity of crops is very important which also depends on the productivity of land. It is determined that if the land productivity is 21–30 points, 0.08–0.09 t of grain are for one point. In medium land that has the productivity of 31–40 points, one point corresponds to 0.07–0.09, and in fertile land with the productivity of more than 40, one point corresponds to 0.06–0.07 t of grain. For example, if economic grade of the farm is 47, its productivity of grain will be about D = 47 * 0.07 = 3.3 t/ha. If the farmer is able to purchase the needed amount of fertiliser and pesticides, has appropriate machinery and knowledge to do everything according to the agrotechnical requirements and adopt the crop rotation, the farmer can expect to get not 3.3 t cereals per hectare, but much more (up to 6-8 t per ha) depending on the yield received during previous years. It is possible to calculate the yield of other crops using cereals productivity and productivity coefficients for the crops (Annex 2.1).
All row crops give the highest yield. New plantation technologies and machinery provide a possibility to plant these crops in such a way that their area could comprise till 30% of arable farmland.
The area of leguminous crops (lupine, peas, vetch, bean and especially clover and alfalfa) is worth to be extended from the economic and ecological point of view.
Especially schemes for purchasing of machinery and technological complexes as well as schemes for production that demands large primary investments (animal husbandry, horticulture, and greenhouse gardening) have to be prepared thoroughly.

2.3
Structure of lands in national parks, reserves and their protective zones could be changed only according to the projects complied with Ministry of Environment and administration of the parks.

Law on preserved territories of the Republic of Lithuania. 1993, V.

More attention should be paid to the protection of environment in preparation of the plans for specialised production on hilly relief, karstic region, river creeks and lakeshores. More extensive agriculture should prevail in permeable light soils where ground water is very vulnerable to pollution.
It is not recommended to plant annual crops in peat soils, because these soils are very valuable for nature. Preference should be given to establishment of meadows and pastures, growing of marsh berries, breeding of waterfowls, fowling, etc. Waters may be flooded, natural meadows and marshes may be restored in order to reduce peat mineralisation.

2.2. SOIL FERTILITY (PRODUCTIVITY)

Fertility (productivity) of the soil is its capability to provide vegetation with nutrients and water. Fertile soil is neutral or close to that reaction, it is enriched with many nutrients; and harmful substances are absent in the fertile soil. During farming, fertility of the soil and its physical-chemical properties must not become worse, i.e. the soil should not degrade (Annex 2.2).
The type of soil, texture, soil heat, water and nutrients regime, the amount of organic matter, microbiological properties and applied agrotechnical measures (soil tillage, fertilisation) determine fertility of the soil. The agricultural activity affects these factors significantly – the activity raises fertility or impoverishes natural environment. Incautious increase of fertiliser rate (besides, plants are not able to utilise such a big amount of fertiliser) wastes money and may escalate environmental pollution.
Biological methods of maintaining and increasing soil fertility are accepted to be the most promising at this time. The following methods are recommended:

1. Proper crop rotations;
2. Enhancement of area of perennial leguminous crops;
3. Use of straw and other organic matter to increase humus content in the soil;
4. Plantation of catch crop for green fertilisers;
5. Liming of the soil.

For better soil fertility one should make use of the natural factors – alteration in soil moisture, deep frost, deep and thick plant roots and favourable activity of micro-organisms. To improve structure of deeper soil layers by mechanical measures under our conditions is not profitable.
Alfalfa, goat rue, red clover, and perennial ear grasses with thick, deep penetrating root system may be planted for improvement of the soil structure.
Shallowly cultivated stubble and partially incorporated chopped straw prompt the mineralisation of organic nitrogen compounds and increase the amount of humus in the soil. The plant residues left on top of the soil prevent the soil from wind erosion. Burning of straw is unacceptable – straw should be composted and used for fertilisation if the area under crop was very weedy.
Agrochemical soil characteristics should be analysed at least every five years in order to regulate plant nutrition and to control soil fertility. These agrochemical characteristics are pH, the amount of humus, mobile phosphorus and potassium.
The main agrochemical parameters characterising fertility of the soil are soil pH, the amount of organic matter, plant available phosphorus and potassium. Besides, useful data are about the amount of Calcium (Ca), Magnesium (Mg) and microelements, such as Copper (Cu), Zinc (Zn), Manganese (Mn), Boron (B), Molybdenum (Mo) and Cobalt (Co).
The amount of calcium, sulphur and other elements in the soil is significant for vegetables, oil plants, and potatoes. As chemical analyses are expensive, it is useful to take advice from consultant agencies and scientists in order to decide which analysis are needed for the fertilisation plans.
An important soil indicator is its structure.
Features of good soil structure:

1. Cultivation of the land is easy.
2. Rainwater is absorbed by the soil quickly.
3. The soil does not become compacted and does not get dry.
4. The soil is sufficiently pressure-resistant (sustains weight of machinery).

Agrochemical characteristics of the soil, which is in a good ecological state, are the following:

1. Soil reaction is neutral or close to neutral;
2. Established balance of organic matter (humus);
3. High biological activity and nitrification capacity of the soil (good utilisation of nutrients, and quick decomposition of harmful organic substances);
4. The amount of harmful substances (heavy metals, pesticides) not bigger or little bigger than the background amount of these substances characteristic to that area.

Acid soils (pH less than 5.5) have to be limed, but not too much, especially peaty and rich in organic matter soils. High amount of calcium stimulates decomposition of organic matter and deteriorates some agrophysical characteristics of the soil.
Soil types according to the storage of organic matter and main nutrients are given in Annex 2.3.
Good soil structure is present only in non-compacted soils. Agronomic evaluation of the density of mineral soils is presented in Table 2.2.

Table 2.2. Agronomic evaluation of the density of mineral soil

Evaluation	Density t/m3
	Arable layer	Subsoil layer
Normal	< 1.4	< 1.5
Partly compacted	1.41-1.5	1.5-1.6
Critical density	> 1.5	> 1.6

2.3. INTENSIVE, SUSTAINABLE AND ORGANIC AGRICULTURE

Till now intensive, also called conventional, agricultural system is applied more often. As prices for fertilizers increase and requirements for products quality become more strict, sustainable (integrated) and organic, or ecological agricultural systems are more widely applied.
Agronomic, environmental knowledge and experience of farmers, local economic, natural-climatic conditions, traditions and technical level affect prevalence of one or another agricultural system. When there was a lack of foodstuffs, the intensive agricultural system was the most prevalent. At present more attention is paid to the quality of the products and environmental protection; therefore, sustainable and organic agricultural systems has a better future.

2.3.1. Intensive agricultural system

Specialisation, concentration and expansion of production amount, mechanisation, application of chemical and biological measures in order to produce more production for sale determines the intensive agriculture.
Plant-growing farms do not keep cattle and therefore, the farms reduce area of grass-plots, do not plant perennial grasses, which are very important for the soil fertility. The fields are not fertilised by organic fertiliser and this reduces humus in the soil. If crop rotation is simpler and the same crops are grown over many years, more mineral fertilisers and plant protection measures are needed to maintain fertility. Step by step the soil becomes exhausted, the plants do not get all the needed nutrients, and the products become more expensive and environmental pollution increases (Fig. 2.2).


Fig. 2.2. When applying the system of intensive agriculture, surplus of nutrients increases price of products and pollutes environment.

The laws of production control and environmental protection and other legislative documents set boundaries for intensification of agricultural production.

2.3.2.Sustainable agricultural system

From an environmental protection point of view the sustainable agricultural system is preferable. Production on the state level is predetermined such (for establishment of the size of quota) that it would satisfy internal needs of the state and existing export obligations. Need of agricultural production is indicated by demand and supply balance that is naturally increasing or decreasing in every state. Level of agricultural production, sale and consumption in every state are shown by statistical data. Allocated quotas help every farmer to find out how much agricultural production he can actually produce. Quotas are not established for the production that has demand temporarily much higher than supply. For example, there are no quotas for mutton in the EU at present. When this agricultural system is applied and production selling quotas are established, then producer have a lower risk investing to the production compared to totally free market.
It is characteristic to the sustainable agriculture that attention is paid not only to economic effect obtained after the end of production cycle and selling of production, but further perspective – production impact on environment - is also considered. For example, when nutrient balance needed for achievement of planned harvest is being made, calculation of spread of these nutrients to environment (water, atmosphere) are also performed and this harm to environment is preferably reduced by production limitation or change of plant growing technologies.
The sustainable (integrated) agricultural system optimises plant-growing and animal production from the economic and ecological point of view, especially in further perspective.
Developing this type of agriculture a farmer applies such crop rotations that increase soil fertility, establishing bigger areas of grassland, leguminous crops, sowing catch crops. The crop rotations prompt the farmer not only to grow plants but also to keep animals. The farms that keep cattle should co-ordinate use of organic and mineral fertilisers. The fertilisers are used to such amount, which is useful for the vegetation, therefore, fertiliser plans, nutrient balances have to be prepared not only for the fields, but also for the entire farm every year. Accounting of farming activities should be performed. Pesticide rates are small and they are applied only when there is a danger for lower yield. Preventive and biological plant protection measures should be applied widely (Fig. 2.3).

Fig. 2.3. In the sustainable agricultural system nutrients and plant protection measures are applied only to such extent, which is needed to receive the planned production

2.3.3. Organic agricultural system

Organic farming is a farming system that is grounded on crop rotation, successive plant growing, diversity of organic fertiliser accumulated on the farm, fertilisation by crop residues, animal manure, leguminous crops, green fertiliser, non chemical control of pest, diseases and weeds. Optimum is when closed energy cycle is implemented. Organic farming significantly restricts or removes the use of mineral fertilisers, pesticides, growth promoters, increasing feeding vitality in this way.
Organic (biological, ecological, bio-organic and bio-dynamic) agricultural system is directed to produce agricultural production that is not polluted with chemical compounds. Natural compounds existing in nature replace mineral fertilisers and pesticides produced by chemical industry.
Farmers may use some of the mineral fertilisers and pesticides in exceptional cases and very limited amount (Fig. 2.4).

Fig. 2.4. In the organic agricultural systems mineral fertilisers and pesticides are used only according Rules of organic agriculture

2.4
Organic farms have to follow requirements of rules for organic farms. The organic farm has to be certificated; its whole production has to be marked with the label of organic production. The farm has to prepare an activity plan, to make crop rotation and fertilisation plans and to carry out the account according to a set form.

Rules on ecological farming: production, processing, realisation, labelling (Lithuanian). - Ekoagros, 1999.

It will be easier to sell organic products, compared to ordinary products, when they are of high quality and when there is bigger and constant production assortment and amount in the country and abroad. Therefore national support, co-operation of processing and realisation are important for development of organic agriculture (it is useful to expand experience of “Tatula program” that has perceived all this).

2.4. CROP ROTATION

Crop rotation solves economical, land use planning and agrotechnical questions at the same time.
Crop rotation – it is the type of arable land use when it is divided to constant and equal fields where crops are rotated according to predetermined order and taking into consideration farm natural, economic and organisational conditions.
Order of crop change is called crop rotation scheme and time period while all crops planned in the scheme pass one crop rotation field is crop rotation period.
Seeking to reduce production expenditure leads to extension of the area under most cheaply grown crops to such extent that there appears a need to grow these crops successively. When in one crop rotation field the same crop is grown a few years it is called successive growing. If the same crop is grown successively for longer time, it is called monoculture and it is not included in crop rotation.
It is also possible to grow successively those crops that occupy small part of all sown area, especially maize if they lack soil suitable for them. An important condition that determines success of long successive growing is absence of pests and pathogens that are spread through the soil. Crop change makes fight against weeds cheaper, then soil water and nutrients are explored better and soil fertility does not diminish for long time.
Even if long successive growing is attracted by its farming simplicity, it is related with big risk to experience huge economic losses for example because of spreading of diseases and pests or because of meteorological conditions unfavourable to grown crops. Successive growing requires more chemical compounds for plant protection and more fertilisers for restoration of soil fertility. At the same time there is increased risk to spread these compounds to environment – to cause harm to nature and humans that are living in that environment.
Use of appropriate crop rotations gives economic and environmental benefit:

1. Natural soil fertility is exploited more effectively, therefore, less mineral fertilisers are applied;
2. Less pesticides needed;
3. Lower risk of the soil erosion;
4. Lower risk of nutrient leaching and pollution of ground and surface water.

Different farm type and farming conditions form very diverse crop rotations. According to the purpose of the crop rotation and grown crops structure, the crop rotations are classified to field, fodder and special rotations. In the field crop rotation cereals and marketable crops comprise more than 50% and fodder crops make up more than 50% in the fodder crop rotation. The special crop rotations are for crops that require certain growing conditions and special agrotechnique. The special crop rotations are of the following types: kitchen garden, nursery-garden, melliferous, herbs and soil protection type.

2.4.1. Crop rotation scheme

Order of crop change should prevent crops from prevalence of the diseases and pests. This is achieved when the crops are sown after break of some years. When other way is impossible and if very good agrotechnique is applied then barley could be sown two three, rye and oat two years successively. To sow wheat and sugar beets successively is risky and to sow flax successively is detrimental. Maize could be resown to the same crop rotation field or sown after one, rye and summer wheat after two, oat, vetch, beans and lupine after three, peas after four, clover after four five (changing species after two four), flax after six and most of other crops after three four years. After successive growing of barley, a break of one two years should be done.
Crops in crop rotation have their own forecrop and aftercrop. Forecrop is a crop that grew in the same field before or is growing now. Aftercrop is future crop that will be grown after harvesting of the latter one.
When deciding on number of the crop rotation parcels, the crops that require longest break are taken into account first. If a farm grows flax, then the rotation has to have not less than 7 members. Clovers need one year for maturity and then they are used for two years, i.e. they occupy the land three years. Because clovers require a break of three four years before second sowing on to the same field, the rotation of this field has to have 6-7 members.
When the number of the crop rotation members is determined, the land area for every member of the rotation is calculated. It is most convenient when the land area is approximately equal to the area needed for at least one crop. Small (10-15% of the area for one member) differences in the sown area are allowed.
The following requirements are raised for good crop rotation scheme:

1. it has to fit to crop structure suitable for farm production specialisation that is discussed in chapter 2.1;
2. there should be kept at least minimal allowed break for every crop to return to the same place;
3. its every crop rotation member has to go after as much as possible better forecrop.

From the crop rotation scheme it is possible to see what part of all area allocated for crop rotation falls to each crop. Assume that crop rotation consists of 8 members and three of them are cereals, this would comprise (100:8=12.5%; 12.5x3=37.5%) 37.5 percents of all crop rotation area. In this way it is easy to check if crop rotation scheme fits to crop structure. If necessary, crop structure could be also changed creatively taking into account possibility to choose suitable forecrops in the scheme.
Crops can be divided into two groups according to their value to serve as forecrops: some of them exhaust soil fertility and do not contribute to its increase, while other crops restore, maintain and increase soil fertility. Crops of the first type are flax and cereals while row crops, leguminous cereals and perennial grasses depend to the second type. In order to locate all crops after good forecrops, it is needed that those crops that increase soil fertility would change crops reducing soil fertility. An example of crops increasing and reducing soil fertility in nine-field crop rotation is given in Annex 2.7.
Examples of the crop combination are the following: potatoes and barley; vetch and oats mixture for green forage and winter wheat; perennial fodder grasses and flax. It is supposed that soil fertility is increased for two three years by mixture of clover and ear grasses, for until one year by leguminous cereals. Row crops increase soil fertility until one year, when machinery is good, crops grown for the green fertiliser (e.g. lupine, vetch) - for two three years.

2.6
Agricultural crops should be grown in crop rotation where forecrops for cereals would be fodder and technical crops. Farmers who cultivate more than 50 ha of arable land should grow at least 20 percent of perennial and leguminous crops.

The most often crops that increase soil fertility cause positive impact on natural environment. Less nitrogen fertilisers will be needed if more leguminous cereals (beans, peas and lupine) are included to the crop rotation scheme. A possibility to plan better forecrops and to change less crop structure with the help of leguminous cereals and perennial grasses is shown in the Annex 2.4.
Row crops may occupy in crop rotation schemes of intensive production till 30 percent of sown area: sugar and fodder beets, potatoes, fodder cabbage and maize. In farms of narrow specialisation there is recommended co-operation between plant production and husbandry farms in order to improve crop structure, to include crops of higher forecrop value to the crop rotation schemes. If we sow spring cereals to the less than 50 percent of all sown area then their forecrops will be good.
Perennial fodder grasses may be planted in order to increase soil fertility and as forecrop in the field rotation. The farms specialising in grain production should plant the grasses only in order not to exhaust the soil. In a case like that, the fodder may be sold or the grasses may be grown for seeds.

2.7
In order to reduce nutrient losses, green (winter and perennial) crops should cover 50% of the total cultivated area on each farm above 15 ha of arable land.

HELCOM 1992 February 6, Recomendation 13/9. Reduction of nitrogen, mainly nitrate, leaching from agricultural land.

Green crops are the following:

1. winter cereals (wheat, rye, barley and triticale);
2. winter rape;
3. clover and other perennial grasses (including cultivated meadows);
4. perennial vegetables.
1. recommendation that green crops would comprise 50 percent of all sown area is easily fulfilled on dairy and livestock farms, especially if cattle are fed with grass fodder. In the field crop rotation there should be grown more winter crops; perennial grasses (clover, timothy and fescue) should be sown to cereals as underseeding crops.
   
   

2.4.2. Crop rotation fields

After the crop rotation scheme is established, then farm arable land has to be allocated (divided) to crop rotations (if there are more than one crop rotation on the farm) and after that crop rotation fields are formed. Some crops (clover, peas, wheat, barley, sugar beets and majority of perennial grasses) grow better on heavier soils (light and medium heavy loam), others (rye, bird's-foot trefoil, kidney-vetches, potatoes, oat, lupine, buckwheat and serradella) on lighter soils (sand and sandy loam soils). If different kinds of soil exist on a farm, more various crops may be grown; however, very big diversity of crops makes management of works difficult.
Sown area planned is different for every crop; therefore, it is not always possible to allocate every crop on a separate field. Some crops may be sown on to one crop rotation field, if they require similar soil tillage, fertilisation, same care and if they leave soil of equal properties. Crops growing on the same field should not hinder soil preparation for other crops, i.e. they should reach maturity at the same time and make it possible to harvest them together. Table showing the grouping of the crops is given in Annex 2.5.
When soil fertility differs, the farmer should first consider those soil properties, which can not be changed. In small farms there may be only some plots with very different conditions for plant growth. Such plots are not included into the crop rotation and they are called non-rotation fields. In larger farms there are bigger areas of cultivated land that differ by soil and therefore several crop rotations can be practiced there.

2.4.3. Realisation of crop rotation scheme

2.4.4.Crop rotation fields in hilly relief and karst zone

Different plant protection measures against erosion make us to distinguish between even areas and rolling areas and between the latter and hilly ones. It is possible to do this according to the inclination of the slopes. The even areas have slopes not bigger than 2-3°, the rolling areas till 5-6°, and the hilly areas till 8-10°. As in plain, in hilly region farmers should seek to have the crop rotation fields of as much as possible regular form – rectangular, trapezoidal and similar. The best solution for usage of steep slopes, tops of hills and fields of irregular form that are inconvenient to be tilled, with crooked ditches and very diverse soil, would be to sow perennial grasses on to them. Areas with degraded soil may be planted with forest.
Perennial grasses should be also planted on the places where are concentrated water flows, along rivulets and drainage ditches.

2.8
On hilly relief farms (fig. 2.7) that have more than 50 ha of cultivated land, erosion preventive rotations (cereals-grasses and grasses-cereals) should be applied or perennial cultivated meadows and pastures should be arranged.

HELCOM 1992 February 6, Recomendation 13/9. Reduction of nitrogen, mainly nitrate, leaching from agricultural land.

Fig. 2.7. Scheme of major slopes inclination in degrees of Lithuanian lands
        In order to reduce ground water pollution the Government of the Republic of Lithuania set up special land use requirements in the protective areas and zone of intensive karst in Northern Lithuania. Majority of instructions regulates the crop structure.

2.9
In the protective areas and zone of intensive karst it is forbidden to use sinkholes as an outlet for subsurface drainage and rainwater.
In the zone of intensive karst, the following crop structure, fertiliser and plant protection systems are set:

1. I group land (under 20 sinkholes/100 ha): Cereals should form not more than 50%, perennial grasses – not less than 40%, and row crops – not more than 10% of the sown area. Yearly fertilisation norm has not to exceed 90 kg/ha nitrogen, phosphorus and potassium (active matter). It is forbidden to use triazine herbicides and chloro-organic insecticides.
2. II group land (20-25 sinkholes/100 ha): It is not allowed to plant row crops and to grow up new industrial gardens. Seven-field crop rotation is applicable for the II group land where cereals occupy about 43% of the sown area and perennial grasses 57%. Yearly fertilisation norm has not to exceed 60 kg/ha nitrogen, phosphorus and potassium (active matter). It is forbidden to use herbicides, retardant and insecticides.
3. III group land (50-80 sinkholes/100 ha): Meadows and pastures of perennial grasses should dominate; cereals may be sown only as forecrop for the grasses. It is forbidden to apply mineral nitrogen fertiliser. Yearly norm of phosphorus and potassium fertiliser is allowed no more than 60 kg/ha (active matter). It is forbidden to use pesticides with exception of mordant.
4. IV group land (more than 80 sinkholes/100 ha):  Only meadows and forests are allowed. Melliferous plants and herbs may be grown. It is forbidden any fertilisation and use of plant protection measures.
5. On I-IV group land a strip not less than 25-m width is left around every pit. Fertilisation and grazing of cattle is forbidden, only mowing is allowed. If landowner or user has signed an agreement to grow organic products on I-IV group land, the crop structure may be not regulated, but the rules on fertilisation and usage of chemical compounds, set for the respective land group, have to be followed.

2.8. Scheme of the Lithuanian karst region: 1 – karst region; 2 – zone of intensive karst; 3 – protective zone

2.4.5. Humus balance

Agricultural plants leave the different amount of organic residues in the soil and the different amount of humus is formed. The amount of humus increases only after perennial grasses. When annual crop is planted, more humus is decomposed than formed. The highest amount of humus is decomposed in the fields with row crop, because intensive care of the crop speeds up mineralisation of the humus (Annex 2.6). Humus balance for the farm is calculated in proportion to the areas occupied by the crops in the crop rotation. Reduction of the humus usually exceeds its formation. In order not to exhaust the soil, it has to be fertilised by manure. 15-12 t of good manure (20-25% of dry matter) is needed for formation of 1 t humus.

2.4.6. Plants of longer vegetation (green crops) and catch crops

2.10
In order to reduce nutrient losses more plants of longer vegetation should be grown in the crop rotation. Catch crops (aftercrops, undercrops and remained stubble) should be grown in the areas of the short vegetation plants and after ploughing of fields in summer.

2.11
In farms of combined specialisation new meadows and pastures should be established on fields that are unsuitable or little suitable for other marketable plants because of moisture conditions and incline, i.e. in the lowest places or on slopes of hills.

During the soil tillage by agricultural machinery weeds, diseases and pests are eradicated, plant residues are incorporated and physical and chemical soil conditions favourable for the growth of crops are provided. The soil tillage is usually related to incorporation of organic and mineral fertilisers, sometimes to the application of pesticides. The tillage of every field depends on grown crops, the forecrop and on the succeeding crop.

2.6.1. General agroecological requirements for soil tillage

Soil should be tilled systematically, with a perspective of at least 2-3 years for every field.

2.12
Soil tillage should be co-ordinated with other measures influencing the yield: crop rotation, fertilisation and sowing. Soil tillage should be carried out when soil moisture is optimal (60-80% of retention capacity).

2.6.2. Agronomic requirements for soil preparation before sowing

2.13
Soil should be prepared for sowing so that at the depth of seed incorporation there would dominate 1-5 mm crumbs and there would be enough plant available moisture in the soil.

Pre-sowing soil tillage in spring depends on biological properties of plant, sprouting and growing requirements and on soil tillage in autumn. Pre-sowing soil tillage should be carried out on depth optimal for the plant sprouting and growing (3-8 cm).
Land for sowing may be prepared by medium heavy harrow (harrowing to 4-5 cm depth) on plain relief where autumn tillage is well performed. If the soil was ploughed worse and it became compacted during winter, then it requires deeper and more intensive soil tillage before sowing by a cultivator (to 6-8 cm) attached in tandem by a harrow (to 4-5 cm). Multi-functional seedbed preparation unit (germinator) is very suitable for the preparation of a good seedbed.
If slopes were ploughed in autumn, then the cultivator should be combined with the medium heavy harrow and the tops and slopes of hills should be sown immediately not waiting until the footslopes dry up. The footslopes should be tilled and sown when they dry up or they should be sown with perennial grasses.
The soil with stubble, which was not cleaned in autumn, but was sprayed by herbicides (of glifosat group), has to be tilled 2-3 times by the cultivator combined with the medium heavy harrow. If the tillage was well performed in autumn, then it is enough to cultivate and to harrow the soil 1-2 times in spring. It is not worth to prepare the hilly soil that does not have many weeds in autumn for the spring sowing, because water erosion increases by 1.6 times in the soil that was ploughed, cultivated and harrowed in autumn; however, such soils dry longer (2-4 days) in spring.
Winter crops. The fields that will be sown with winter wheat, rye, triticale and barley should be well levelled in order not to leave small depressions, which can collect water in autumn and winter. Levelling is performed after stubble cleaning, before deep ploughing. Before sowing the soil is shallowly loosened then the seeds lie down on harder and wetter sole, germinate better, strike stronger root and suffer from unfavourable meteorological factors less. Field for winter crop should be well levelled in autumn and loosened before sowing to the depth optimal for plant seedbed.
A heavy harrow (to 5-6 cm) before sowing should harrow lighter textured and not so dense soils twice. Heavier and compacted soils need deeper cultivation (to 8-10 cm). Winter wheat seeds are best incorporated in 3-5 cm depth. The optimal sowing depth for winter rye seeds is 3-4 cm in heavier soils and 4-5 cm in lighter soils; triticale seeds are sown into a depth of 3-4 cm in heavier soils and into 5 cm in light soils. If seeders are properly adjusted, seed is sown only 0.4-0.5 cm deeper into the soil that was deeper cultivated before sowing than into the soil that was prepared only by a harrow. After sowing the surface of soil has to be even assuring equal conditions for the germination of all seeds.
Spring cereals. Spring barley has to be sown early, when soil starts to crumble during harrowing. Soil preparation begins in light soils, because moisture evaporates quickly from these soils. The heavier soils are, the more accurately preparation time is chosen, because appropriate maturity period of heavy soils is short, even if it is later than that of light soils. Early sowing but not soil tillage before sowing predetermines yield of spring barley in soils of heavier texture. In loamy soils every additional day after the optimal sowing time reduces yield of barley by 50 kg/ha on average. Agrotechnical sowing period of barley is 6 days. The optimal barley sowing period may last for 9 days evaluating economic and organisational aspects. Barley and wheat should be sown in 6 days and oat straight when it becomes possible to start harrowing.
In light soils the type, intensity and depth of the soil tillage do not influence yield of spring barley if sowing is performed on time. The light soil may be prepared only by heavy harrow in spring, and cultivator should be used only in very weedy soils where tines would lift underground parts of couch-grass and other perennial weeds on the top of soil and they would dry up. The best germination conditions for spring barley are when soil is tilled and barley is sown at 4-5 cm depth. Long-term meteorological data shows that it rains every third day in spring on average. It is important to take this into consideration during planning of sowing, in order to sow up every field straight after its preparation, because otherwise it will be needed to prepare the soil once again and to delay sowing when waiting while the soil gets dry enough.
Spring wheat has to be sown together with other early sown cereals, after oats and before barley. Soil for spring wheat has to be well loosened in spring. In worse tilled soil the seeds germinate worse and the crop field becomes sparse. The same agricultural equipment is used for soil preparation before sowing as for other cereals. In light loam soils the highest yield of spring wheat is achieved when the soil is loosened deeper than 5 cm before sowing. In heavy loam soils the best yield is achieved by loosening the soil by spring-tine cultivator to 10-cm depth before sowing. The seeds are drilled at 3-5 cm depth.
Sowing time affects productivity of oats more than productivity of barley. Their germination requires a lot of moisture (60-100% water of grain mass); therefore, oats should be sown first. Delaying soil tillage and sowing, oats more suffer from diseases (crown rust) and their yield diminishes. Every delayed day in oats sowing, in comparison with early sowing, reduces grain yield by 36 kg/ha. It is enough to cultivate light soils with harrow only once in spring. As soon as the soil becomes dry enough, it should be harrowed and sown with oats. Deep (to 12 cm) loosening of not weedy soils of good structure does not affect oat productivity more than loosening to a depth of 5 cm. In heavier soils oat seeds are sown at 3-4 cm and in lighter soils a little bit deeper at 4-5 cm.
Leguminous. Soil for peas, vetch and beans that was well ploughed in autumn may be prepared only by a heavy harrow in spring. If the soil is badly ploughed, it should be cultivated by the cultivator combined with medium heavy harrow. More humid soils are first cultivated to a depth of 6-10 cm and after that – to 10-12 cm. To break up soil too much is not useful especially in heavier soils, because the germinating crop receives less air then. Medium heavy and heavy soils have to be harrowed 2-3 times. In medium heavy soil the optimal depth for sowing of pea seeds is 4-6, in heavy 4-5, in lighter 9-10 cm. In heavier loam soils vetch is sown at 3-4, in lighter loam at 4-5 and in sandy loam at 5-6 cm. Beans sowing depth is 5-8 in heavier soils and 6-8 cm in lighter soils. Peas, vetch and beans should be sown as earlier as possible straight after it becomes possible to work the soil.
Light and not dense soils that were well ploughed in autumn may be prepared for the sowing of lupine only by a harrow in spring. Lupine yield is not higher if the light soil is cultivated and harrowed than if it is only harrowed. Just compacted soils require shallow cultivation. Lupine germinates well when their seed is sown at a depth of 3-4 cm. If the seeds are drilled deeper, germination rate reduces by 25-50%.
Buckwheat is sown later than any other spring crop, because it is very sensitive to frost; therefore, the soil ploughed in autumn is cultivated a few times before sowing. First time the soil is cultivated and harrowed when it becomes dry enough. If it is needed weeds are eradicated before sowing. Such handling eradicates the main weeds present on the top of the soil. In light soils buckwheat seeds may be sown at 7 cm depth and in heavier soils at 4-5 cm depth.
Potatoes. Potatoes like loose soil. In light sandy loam soils deeper ploughing in autumn is not of great use to potatoes. When planting potatoes after cereals it is important to cultivate the stubble and then later in autumn to plough the whole arable layer of the soil. It is known that the weeds reduce 4 times if the stubble is cleaned. Potatoes should be planted on not weedy well-loosened warm (to 5^o C) soil.
Planting potatoes after legumes or other late harvested crops there is no time for stubble cultivation; therefore, the field is ploughed deeply at once. The soil, which was ploughed in autumn, has to be harrowed first, then the soil warms up quicker, weeds germinate earlier that are eradicated later during cultivation and harrowing. If potatoes are grown without herbicides, it is the most rational to cultivate them five times – three times by hiller combined with network harrow before sprouting and two times by hiller after sprouting of the potatoes. In very weedy soils weeds may be eradicated also by herbicides. The best is to combine application of herbicides with hilling up of the potatoes. Even if herbicides are suitable to eradicate weeds in potatoes crop, farmers should try to avoid use of herbicides, especially for potatoes grown for seed and food.
Flax. In light loamy soils with many perennial weeds the highest yield of stems and linseeds and the lowest amount of weeds are in the soil that was stubble cultivated and ploughed in late autumn. The lowest yield and the highest amount of weeds (especially perennial ones) are in the soil that was ploughed early autumn. Soil preparation for flax in spring has an aim to eradicate weeds, to preserve more moisture and to loosen the topsoil. It is useful to cultivate the soil not deeply and to harrow it before sowing of the flax. The highest yield of fibre and linseed is achieved when seeds are sown with row spacing of 7.5 cm sowing the seeds at 1.5-2 cm depth. The sown field should be rolled.
Sugar beets. Sugar beets grow best in light loamy soils. The soils are stubble-cleaned and ploughed or stubble-cleaned, levelled and ploughed in autumn. It is not advisable to level the ploughed soil, because then it dries longer in spring and the work starts 2-4 days later. It is not useful to level the soil in spring as well, because the yield reduces. In spring when soil conditions allow, the field is harrowed. Loose soil is cultivated by harrow and compacted soil is shallowly (at a depth of 6-8 cm) cultivated and harrowed and it is rolled before sowing. The seeds should be sown at 2-3 cm in heavy soils and at 3-4 cm depth in light sandy loam soils.
Winter oil-seed rape. After harvesting of forecrop the soil for winter rape is prepared in the same way as for other winter cereals. If rape is sown after the early mixtures harvested for green forage or after perennial grasses of first cut, it is important to clean the stubble and to plough deeply. Sowing rape after cereals, the forecrop is harvested late and there is no time left for cultivation of the stubble. In such a case the soil is ploughed deeply at once. In any case the soil has to be ploughed deeply not later than two weeks before sowing in order to leave the time for natural compaction of the soil. If soil is too loose, the field should be rolled. When field is properly ploughed, light soils may be prepared by a harrow. If a spring-tine cultivator prepares soil, it is important to loosen it shallowly. Before sowing of rape all soils are necessarily rolled by circular role. Plants have high yield potential when they are drilled to a depth of 1-2 cm with 12.5-cm row widths, followed by rolling.
Spring oil-seed rape. In autumn soil is tilled for spring rape in the same way as for spring cereals, but it is rolled necessarily. Spring rape is sown in early spring together with the early cereals. The seeds are sown at 1-2 cm depth in heavier soils and 2-3 cm in lighter soils. The fields should be rolled after sowing again in order to even up and to quicken ripening of the crop.
Clover. As clover is sown into cereals or in the mixtures used for forage, soil is tilled according to requirements of the covercrops. It is important that the soil would not be weedy as weeds especially couch grass are very detrimental to clover. Clover is sown into spring cereals during sowing or after sowing of the spring crops and into winter rye as soon as soil conditions allow. In medium heavy soils clover seed is best drilled to 1 cm and in light soils to 2-cm depth. Proper sowing of the seed requires rolling of the field before sowing. The field is rolled once again after sowing.

2.6.3. Manoeuvres of agricultural machinery and soil compaction

Fertility of over compacted soil is always lower. Headlands sown with permanent grasses, which can be installed if land is used extensively, suit for passes of agricultural machinery the best.
Soil compaction risk may be reduced if choosing better tillage time and adjusting power of agricultural machinery and equipment to power needed for soil tillage.

2.14
Agricultural machinery has to move on fields in such a way, that soil would be less compacted, crushed and grinned.