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PROTECTION OF AGRICULTURAL LANDS
I INTRODUCTION 68. As almost 60% of Poland's area is used for agriculture, protection and maintenance of the fertility of such areas is extremely important. Agricultural lands include arable lands, fish ponds, peatlands, water eyes, and lands built on with farm buildings. Differences in plant cover as well as the preponderance of light and very light soils, cause farmers to take special care of the physical, chemical and biological properties of the soil so it can keep all the functions required for food production. The Code presents the main threats, which may lead to irreversible or difficult-to-reverse changes of soil properties (they may limit growth and yield of plants) and describes methods of protecting lands from various kinds of degradation. In order to protect soil according to the rules presented in the following chapter, each farmer must know the basic properties of the cultivated soils. The most important source of information on the soil should be a soil-agricultural map made for individual farm and results of periodical analyses of soil fertility and its acidity. These analyses are made by agro-chemical stations.
II LAW PROTECTING AGRICULTURAL LANDS 69. The most significant document concerning the protection of agricultural lands is an Act on protecting agricultural and forest lands of 1995, which defines ways and methods of protection [10]. They are as follows: § limit their use for purposes other than agricultural; § prevent such lands from devastation and degradation; § recultivate and use them for agricultural purposes; § maintain peatlands and water eyes as natural water reservoirs.
III PROTECTION OF LANDS FROM DEVASTATION AND DEGRADATION
70. A farmer is obliged to counteract degradation of land, especially to protect it from erosion. WATER EROSION 71. Water erosion causes damage both to the surface and to deeper layers of the soil and translocation of mineral nutrients from the soil to surface water. Water quality is especially threatened by biogenic elements such as nitrogen and phosphorus. Activities, the goals of which are to protect soil from water erosion, apply also to water protection. Figure.
Field damaged by heavy summer rain
72. A farmer can prevent lands from erosion mainly by organising crop production properly and applying agricultural treatments aimed at combatting erosion. Lands with slopes greater than 20% (12°) should be permanently grassed or afforested. Lands with slopes between 10 and 20% (6 - 12°) may be used for field production, provided some agricultural treatments, preventing them from erosion are applied regularly. Lands with slopes of less than 10% (up to 6°), especially those on long slopes are less threatened with water erosion, but it is advisable to cultivate such lands in a special way.
Hill-side terraced by continually ploughing across the slope
73. All agricultural treatments including sowing and planting should be done across the slope. It is recommended to use reversible balanced ploughs that turn the ridge to the top of the slope. Figure
Tractor-mounted reversible plough
74. All soils located on slopes must not be ploughed but tilled without turning the soil. It is better to do primary tillage with tine cultivators with feet (duckfoot cultivators) and pre-sowing tillage with passive tool set consisting of a harrow or tine cultivator followed by a cage or surface roller. 75. An additional anti-erosion treatment (subsoiling) may be applied on soils strongly susceptible to erosion. It is based on making vertical cuts in the soil, the aim of which is to increase water retention and to increase the speed with which water soaks into its deeper layers. Subsoiling is done with a special tool - a subsoil plough - which requires a high-power tractor. 76. Gullies occurring within agricultural lands should be managed in order to prevent their further development. Gully management requires costly treatments and it may be supported by the National Fund for Environmental Protection. 77. Erosion may reduced considerably if anti-erosion crop rotations are used. They must consist of papilionaceous plants, their mixtures with grasses, as well as winter crops ("green fields"). Winter rape, rye and triticale are highly recommended because they can produce dense canopies as early as in the autumn. 78. If a preceding crop is harvested early and then followed by a spring crop, it is essential to grow an intervening stubble crop or a winter catch-crop to keep the soil covered. Stubble crops should not be ploughed before winter, in order to leave a mulch. 79. Unsown areas should be covered for autumn and winter with different mulching materials such as straw, potato stalks and leaves. 80. The occurrence and amount of water erosion depend on the amount and intensity of rainfall, slope of the land, soil type, and finally on plant cover.
Strip fields situated along loess slope divided by road gully
81. The susceptibility of soil to erosion is connected with its mechanical composition and structure.
WIND EROSION 82. Wind erosion is especially harmful to the surface layer of the soil (it is blown away), to the plants (they are mechanically damaged), to the root system (it is exposed) and finally to the natural environment (air and water become polluted with dust particles from the soil). Protection of soil from wind erosion is also important for both air and water protection. 83. Dusts blown away are harmful as they carry organic and mineral nutrients and pesticide residues. 84. Establishment of shelterbelts of bushes and trees and maintaining the soil under plant cover seem to be the most effective treatments to protect soil from wind erosion. Figure. 85. On soils and areas especially threatened with wind erosion, soil should not be ploughed or otherwise inverted. Plants should be sown immediately after tillage whenever possible. 86. Sand dunes occurring within a farm must be planted with trees. 87. The intensity of wind erosion depends on the wind speed and frequency of its occurrence, the soil type, the landscape diversity, and the kind of plant cover.
Network of planted shelterbelts
88. Wind erosion causes the greatest damage on plain agricultural areas where the soils are susceptible to be blown away, and on those without shelterbelts of bushes and trees. Stand damage most frequently occurs in the early spring.
CHEMICAL DEGRADATION 89. Chemical degradation - is the heavy soil contamination caused by harmful chemical substances such as heavy metals, polycyclic hydrocarbons, and pesticide residues. Under particular circumstances, excessively high rates of mineral and organic fertilisers can also have adverse effects. 90. Critical contents of heavy metals in the surface layer of different categories of soil are given in Annex 5. As regards soil contamination with heavy metals, there are the following classes:
91. Soils with natural or increased contents of heavy metals may be used to grow all plants for people's food or animal feed. 92. Soils contaminated or heavily contaminated require special treatments that are recommended by local agro-chemical stations. 93. Sludge cannot be applied on soils which have increased amounts of heavy metals (contamination class I). Neither sewage nor sludge is allowed to be used on soils that are slightly contaminated (contamination class II). 94. In order to avoid contaminating soil with pesticides, it is essential to take the following measures before they are applied: § estimate precisely the health condition/infestation level of the particular crop, § get acquainted with the reports of the State Inspection of Plant Protection and Agricultural Advisory Centres, § analyse the possibilities of applying integrated protection, which may need only to be supplemented by pesticides, § choose pesticides that are the safest for the environment (soil, water and air), § avoid applying pesticides which decompose slowly, or are of low selectivity, or those which are recommended to be used at high rates, § apply pesticides according to the instructions which must be read thoroughly before the pesticides are used. 95. Rates of pesticides used on big fields should vary according to the intensity of the particular pathogen. In case of plants grown in wide rows, herbicides may be sprayed in strips, which reduces the amounts reaching the soil environment.
SOIL FERTILITY 96. Protection of agricultural lands is primarily meant to maintain and increase soil fertility i.e. the physical, chemical and biological properties which allow high yields of good quality to be obtained. The basic agrotechnical treatments regulating soil fertility are as follows: crop rotation, mechanical tillage, and mineral and organic fertilisation. Soil reaction (pH), contents of available nutrients and organic matter, and air-water relations are important for soil fertility. 97. Soil fertility should be maintained or increased as a result of agricultural activities.
SOIL REACTION (pH) 98. Soil reaction is the result of natural processes taking place in the soil and may be affected by the farmer. Such an influence depends on the soil type, the crops being grown, and other agricultural practices. Top-soil reaction may be improved by liming. Proper soil reaction is required for the efficient utilization of nitrogen, phosphorus and potassium fertilisers. 99. A farmer can, through the proper Agricultural Organization, obtain some funds for buying lime and lime-magnesium fertilisers. The state subsidies will be granted as soon as up-to-date results of soil analyses and liming requirements are presented. 100. Soil reaction of the ploughed layer should be maintained within the optimal ranges for the plant species being grown.
Relation between soil conditions and its reaction
101. Soil reaction (pH) is the easiest value to be measured. The pH of soils used for agriculture should range from 4,5 to 7,0. Values of pH lower than 4,5 indicate soil chemical degradation, whereas values higher than 7,0 indicate alkalisa tion, harmful for both growth and development of plants and for the soil. The optimum value of soil reaction depends on the soil type and the choice of plants in the crop rotation. 102. Soil reaction must be analysed every 4-6 years by the local agro-chemical stations. The results should be presented as maps of soil reaction and liming requirements.
103. Rates application of lime and lime-magnesium fertilisers should be based on fertilisation advice. Fertilisers applied at rates higher than recommended may cause over-liming of the soil and have negative effects on its fertility and productivity. 104. Grasslands of pH lower than 6.8 should be limed in the same way as agricultural lands. Lime fertilisers should not be used on organic soils (peat, muck) of pH higher than 5,0. 105. Soils, which are not agriculturally used (idle lands, ecological areas), especially those located within protective and sensitive water zones, should not be limed. 106. Lime fertilisers should be applied after harvest and mixed with the soil (using a plough, cultivator or a powered tool). Direct contact of lime fertilisers with organic ones is not permitted due to possible nitrogen losses. On plain areas lime fertilisers may be used on frozen soil. Permanent grasslands should be limed in autumn or winter.
Lime spreader
107. Lime fertilisers should be spread with special, well-regulated distributors which provide a uniform distribution on the field. It is not advisable to use manure spreaders for this purpose. Uneven distribution may lead to local over-liming. 108. Soils may be deacidified with lime fertilisers, which have been admitted for the market by the Polish Norm. Such fertilisers are safe both for the soil environment and for plants. 109. A farmer has a right to claim a certificate with each purchase of lime and lime-magnesium fertilisers. The percentage contents of calcium and magnesium stated in the certificate are essential to determine rates of application of fertiliser per hectare.
CONTENT OF AVAILABLE NUTRIENTS 110. Plant growth may be regarded as optimal if plants are supplied with appropriate amounts of available forms of both macronutrients (nitrogen, phosphorus and potassium) and micronutrients (boron, zinc, manganese, copper and molybdenum). Excessive rates of application of nitrogen fertilisers lead to accumulation of mineral nitrogen, nitrates and ammonia ions in the soil and then to their translocation to ground waters. Lack of one nutrient means that others may appear in surplus. Therefore they may accumulate in the soil or leach to ground water. 111. Lack of basic nutrients must be complemented by mineral and organic fertilisation, and their availability regulated by soil liming. 112. Content of available forms of macronutrients should be analysed every 4 - 6 years by the local agro-chemical stations. Analysis of micronutrients is essential only if deficiencies are likely to occur. 113. Soils having medium contents of nutrients (which is regarded as optimal from the productive, economical and ecological points of view) should be fertilised according to plant nutritional requirements (so-called balanced fertilisation). 114. On soils containing either very low or low amounts of nutrients, it is essential to use more nutrients than the crop requires in order to bring the soil up to medium content. However, with regard to nitrogen, it is not allowed to exceed optimum rates.
115. Local agrochemical stations present the results of soil analyses as ranges of nutrient content and these are shown as appropriate colours on the map of soil fertility.
116. Nutritional requirements correspond with the amount of nutrients in the final crop yield and may be calculated from expected yield being multiplied by the average content of particular nutrient in the yield (Annex 6). 117. Rough estimates may be based on the average nutrient content in grain unit (1 grain unit corresponds to 100 kg of cereal grain, or 400 kg of potato tubers, or equivalents for other crops).
118. Soils with low contents of available phosphorus and potassium have low productivity and the process of enriching such soils with these nutrients is very difficult, even if high rates of fertilisers are used. Therefore it is advisable to maintain appropriate contents of nutrients and avoid their depletion. 119. Soils containing low amounts of nutrients are regarded as chemically degraded and must be rehabilitated, which is a very costly treatment.
BIOLOGICAL PROPERTIES OF THE SOIL
120. In order to maintain soil fertility at the appropriate level it is necessary to take care of its high biological activity. 121. There are various kinds of organisms (fungi, bacteria and small animals) living in biologically active soil. Each species plays particular roles in maintaining soil fertility. 122. Earthworms, which can easily be seen with the unaided eye, are very sensitive to different kinds of soil pollution. The greater the number of earthworms, the more fertile the soil is. 123. Excessive amounts of mineral and organic fertilisers, which contain ammonium nitrogen (slurry) may reduce the number of earthworms in the soil. Therefore it is necessary to avoid applying slurry on soils that are too wet or which are only slightly permeable. Well-decomposed farmyard manure or compost increases earthworm populations. Growing grass or retaining considerable quantities of stubble residues can have the same effect.
A vertical earthworm tunnel and excreted soil on the surface
124. Earthworm populations increase in soils that are shallow-tilled and in those in which mechanical tillage is limited. This is because ploughing destroys the channels made in the soil by earthworms and degrades the air-water relations in the soil.
SOIL ORGANIC MATTER 125. Fertile soil, subject to its mechanical composition should contain a certain amount of organic matter, which affects the biological, physical and chemical properties of the soil, but first of all its structure, water capacity, content and availability of mineral elements, resistance to erosion and chemical degradation. 126. Proper management is aimed to maintain or increase the content of organic matter in the soil. 127. It may be obtained by selecting suitable plants for crop rotations and using organic fertilisers regularly. Processes of decomposition predominate in fields under root crops, cereals and maize, and processes of organic matter accumulation predominate in those under perennial crops. Particularly high accumulation of organic matter occurs on grasslands. 128. Changing land use from permanent pasture, grassland or forest to arable causes rapid decomposition of organic matter and the release of great amounts of easily-soluble organic and mineral compounds. Such a situation creates a danger of water contamination with substances causing its eutrophication or deterioration of drinking value. 129. Fertile soils having desirable amounts of organic matter contain a lot of earthworms, have a characteristic smell and feel springy underfoot. All these properties make such soils easily recognisable. 130. Fertile soils are distinguishable by a balance between the organisms that are harmful to plants and those, which are beneficial for them. Such a balance is regulated by a proper crop rotation.
AIR-WATER RELATIONS OF THE SOIL 131. The structure, which is a result of soil properties and its method of management, govern the air- water relations. 132. Soil with a good structure can provide proper air-water relations, essential for plants and various soil organisms. 133. Structure is to a great extent an effect of the farmer's activity and results from: § selecting appropriate plants for the crop rotation, § conducting various agrotechnical treatments, which make the soil loose and change its level, § changing soil reaction, applying organic fertilisers, § removal of excess water through an efficient drainage system.
Soil profiles showing structure
134. The method of soil tillage must be adjusted to the following factors: condition of the field after harvesting the previous crop, the soil type, requirements of succeeding crop, equipment used, weather conditions and length of the period between harvest of the preceding crop and the optimum date for sowing the succeeding crop. 135. Ploughing is one of the basic tillage treatments. Its depth should not exceed 20 - 25 cm, especially on light soils containing little organic matter. Otherwise it may lead to significant mineralisation and high nutrient losses or their excessive dilution.
Balance plough
136. Agricultural treatments should be conducted as often as is necessary to provide plants with optimum growth conditions, but at the same time their intensity should be as low as possible. 137. Excessive soil compaction, especially in the deeper soil layers, limits root growth and water percolation and can also lead to soil erosion. Such a soil may also get flooded after heavy rains. Limited air access to the deeper layers reduces biological activity which in turn influences its fertility and reduces the availability of nutrients for plants. 138. In order to reduce such negative effects on very moist soils, it is necessary to avoid using heavy equipment and/or to use dual or wide wheels, which reduce the pressure on the soil surface. 139. Ploughing, when it is done at the same depth for many years and when it is done on soil which is too wet results, especially on clay soils, in the development of a plough sole, which can prevent water, air and plant roots from penetrating into deeper layers of the soil. 140. Physical properties of the soil may be improved by using a tine in the furrow bottom, which breaks-up the plough sole and loosens the subsoil. 141. If bad structure (thick/compact) is accompanied by low content of organic matter, it is advisable to grow a mixture of grass and papilionaceous plants for for 2-3 years. 142. Different methods of soil tillage must be adjusted to various crops forming a crop rotation within a farm. They play beneficial roles for improving air-water relations in the soil.
Conservation tillage with gruber
143. Regulation of water-air relations is very important on grasslands as they determine the development of desirable meadow plant species (grasses, papilionaceous plants, herbs). 144. An appropriate land drainage system seems to be the basic treatment regulating air-water relations on permanent grasslands. 145. Farmers, using drained lands, should feel responsible and take care of any network of drainage ditches on their fields. 146. The maintenance of a water management system (drainage and irrigation) should be conducted by qualified water service technicians according to technical-agricultural principles of object exploitation.
A ditch overgrown with
147. The time of starting drainage or irrigation depends both on the level of the ground water as observed in observation wells and on the water level in the ditches. 148. The majority of lands that have been drained so far become degraded as they were excessively drained. The network of ditches forming the drainage system is often neglected and does not play its role. 149. Big complexes of permanent grasslands, especially those located on former bog soils require new drainage systems. These treatments are very costly, and may be accomplished with state subsidies.
Observation well 1. water wellpipe of poliwinyl chloride PCV pipe 2. top plate of reinforced concrete 3. reinforcing fabric 4. wooden pipe plug 5. perforated part of the pipe (all in cm dimensions are)
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