Environmental degradation is a quick and adverse process to the surrounding nature. In case of agricultural land it can lead to disturbances in soil, irreversibly inhibiting the process of soil formation (Code of Good Agricultural Practice, 2004). Deteriorating physical, biological and chemical properties of the soil, effects of limiting production and greatly reduce soil fertility.

 

The consequences of environmental imbalances may be global, where the only way to preserve the balance is the policy of interdependency, which based on controls and sanctions, that keeps the highest standards (AgriLife,

2009). The European Union (EU) conducts policy, in which farmers must comply with standards and rules to maintain the liquidity of European subsidies. The cross compliance rule is consistent with the environmental standards of Good Agricultural and Environmental Conditions (GAEC) (2014), which are directly relevant to the protection of environment, public health, plant and animal welfare and the maintenance of agricultural land according to the principles of agricultural and environment respect (MRiRW, 2013). These standards are described in the regulation of the signature 2009/73/EC, established within the EU (Directive 2009/73/EC). Directive regulates the political establishment and obliges all EU members for direct implementation of the provisions.

 

The rational agricultural land use in the main part lays on the responsibility of all agricultural entrepreneurs. Maintenance of land cultivation in proper condition, leads to the appropriate elemental soil saturation (Stachowicz, 2010), creating the crop yields of high quality (Smagacz et al., 2010). To apply appropriate doses of minerals for selected crops, the optimal mixture of synthetic fertilizers and natural manure should be prepared (Czuba, 2001; Kopi?ski, 2010; Fotyma et al., 2010; Tujaka, 2010). Fertilizers supply the soil with nitrogen (N), phosphorus and potassium in form of oxides P₂O₅ and K₂O (Konieczna and Roman, 2014). The most common way of selection of the mineral value of soil is the method "on the surface of the field" (Nowak, 2013), which is the procedure to monitor the balance of NPK in the soil. This tool is described in the Regulation of the Minister of Environment, 2002 (Dz.U. z 2003 r. nr 4, poz. 44). According to the regulations of Polish directives, the level of nitrogen supplied to the soil with fertilizers should not exceed 170 kg N/ha (The EU Nitrates Directive, 2010).

 

The aim of research was to determine the balance of NPK fertilization in technology of corn for silage, sugar beet and meadow grasses production. The following research hypothesis was formulated: Did the physicochemical properties of the soil and controlled growing conditions by optimal selection of technology result in cost reduction of the crop production allowing at the same to rational use of natural resources.

The NPK balance method was used as described by Code of Good Agricultural Practice (2004), explaining how to determine the needs for individual elements of selected crops. The method relies on the balance between the volume of elements supplied to the soil contained in synthetic fertilizers as well as in the natural manure and the value taken up by the crop during the growing season. Survey data were grouped for each type of crop, for which individual technological cards prepared for each farm. Analysed crops were: corn for silage, sugar beet and meadow grasses. In surveyed farms, plants were cultivated on soil of the average bonitation class (IV-th class of soil), by the conventional crop production systems. The study was conducted on the 30 surveyed farms in Poland, in which the groups of 10 crops of corn for silage, 10 crops of sugar beet and 10 crops of meadow grasses (Table 1) were specified. The balance of the organic substance may be monitored, according to the Formula (1).

 

 

Where: S – balance of organic matter [t·ha^-1], W – coefficient of soil reproduction or soil degradation of organic matter for crop [t·ha^-1], P – coefficient of soil reproduction of organic matter for undersown plants, catch crops and mulch [t·ha^-1], N_o – farmyard manure fertilization [t], W_o – coefficient of soil reproduction of organic matter for farmyard manure [1·h^-1], N_g – liquid manure fertilization [t], W_g – coefficient of soil reproduction of organic matter for liquid manure  [1·h^-1], N_gn – slurry fertilization [t], W_gn – coefficient of soil reproduction of organic matter for slurry [1·h^-1], N_s – straw fertilization [t], W_s – coefficient of soil reproduction of organic matter for straw [1·h^-1],

 

The coefficient of soil reproduction and soil degradation of organic matter was derived from Code of Good Agricultural Practice (2004). To conduct the balance of fertilization needs in the technology it is necessary to use the Formula (2).

 

 

Where:S_NPK – balance of NPK demand for crop [kg·ha^-1], N_NPK – NPK applayed by fertilization [kg·ha^-1], Z_NPK – NPK demanded by crop [kg·ha^-1],

 

Discharged value of NPK (Z_NPK) that were demanded by the each particular crop has been derived from Code of Good Agricultural Practice (2004). The level of NPK values (N_NPK) that were supplied by fertilization were gathered from crop technology survey and presented in the Table 1. Fertilizers were applied by agricultural machines, which were located on the farm as a technical equipment. Natural manure were derived from livestock on the farm.

 

The analysis required the usage of dedicated computer software, which analytical module based on a mathematical algorithm. Algorithm allows to estimate the balance of NPK nutrients, humus content and level of nitrate nitrogen in the soil. The summary of data that was described in Table 1, shows the balance of NPK based on studies which were conducted on the surface of the field (Jo?czyk and Stalenga, 2006). The study used the "P.W. 3.3" computer program, which was created in the framework of the Multiannual Programme 2011-2015 titled "Standardization and monitoring of environmental projects, agricultural technology and infrastructure solutions for security and sustainable development of agriculture and rural areas" in Activity 3.3 titled: "Monitoring the effectiveness of the installation and agro energy efficiency of use of raw materials". Designed computer program, requires declare to variables for each crop. Input parameters in the analysis were type of soil, yield value and the level of synthetic fertilizers and natural manure. The analysis of particular crop was based on the phased specification of parameters characterizing the agricultural activities, under which the program calculated the balance of NPK, depending on factors specific to the technology.

 

 

Builded for the project realization (Multiannual Programme for 2011-2015, Activity 3.3) computer program and database, were created on the base of the principles of the Code of Good Agricultural Practice (2004). The program allows to perform calculations for the technology of the following crops: corn, beets, grains, legumes, meadow grasses and grain mixtures. The computer program database has also declared information concerning the content of chemical compounds (nitrogen, phosphorus oxide and potassium oxide) in particular synthetic fertilizers and natural manure. The contents of natural manures were presented in Table 2.

 

The computer program also prepares and declares database of synthetic fertilizers and natural manure, which can be modified according to the specific research needs. The coefficients of nutrients in fertilizers allow for calculation of the NPK balance using the data declared as an integral part of the used technology. The values of each chemical fertilizers are summarized in Table 3. The computer application was used as a tool for monitoring changes in the elemental content of the topsoil, influence of agrotechnical activities, which are contributing to the reduction of groundwater quality. Algorithm is also equipped with a module to estimate the value of nitrate nitrogen in the soil (N_NO3) depending on the crop. The value of nitrate nitrogen as an indicator of the potential environmental hazard (IUNG-PIB, 2008) was dependent on several weather stations in Poland, by analyzing the annual rainfall for that area.

 

 

 

All analyzed technologies have individual level of fertilization depending of quality and quantity. Calculations include the value of delivered nutrients from synthetic fertilizers, natural manure and aftercrops during the cultivation.The volume of NPK by which the technology has impoverished the soil, was determined in content of elements in the crop yields. Summary of applied synthetic fertilizers and natural manure in analyzed technology of sugar beet, corn for silage and meadow grasses were presented in Table 4.

 

Tables 5 to 7 summarizes the results of NPK balance calculation from delivered and received nutrition for each crop. The calculations are characterized by maintaining the balance of nutrients in the soil during the cultivation of individual plants. The EU Nitrates Directive (2010) specifies the maximum value of nitrogen that can be delivered to the soil from the natural manure per year. The diagram (Figure 1) shows that the most of technologies were close to the upper level of allowed nitrogen fertilization value. The average content of nitrogen that was applied with natural manure amounted to 149.5 kg•ha^-1, and the average nitrogen value applied with the synthetic fertilizers amounted to 118.8 kg•ha^-1. Presented diagrams characterize the content of nitrogen, phosphorus oxide and potassium oxide in the soil for individual cultivation technologies (Figures 1 to 3). The positive and negative value of balance, were derived from calculation of NPK demand of crop (Formula 2).

 

The average content of phosphorus oxide that was applied with natural manure amounted to 94.0 kg•ha^-1, and for synthetic fertilizers amounted 55.2 kg•ha^-1. With respect to the potassium oxide values were respectively: for natural manure 153.1 kg•ha^-1, and for synthetic fertilizers 69.1 kg•ha^-1.

 

 

 

 

 

 

 

In the case of natural fertilization excess may be caused by animal waste overproduction in the survey farms overproduction of natural wastes could be better utilized for biogas production. If the natural manure content 0.5% (Table 2) of nitrogen. According to average excess of nitrogen is 98.29 kg·ha^-1, it can be calculated that 19 658 kg·ha^-1 of natural manure is wasting every year on the field. Natural manure consists 60-80% of dry organic matter, that gives the capability of 300 to 700 m³·t^-1 of biogas production (Fugol and Szlachta., 2010). Overproduction of wasted natural manure could generate 6 290 560 m³ of biogas, that gives 3 774 336 m³ of pure methane (CH₄) every year.

The author(s) have not declared any conflict of interests.

The article was created under the framework of the Multiannual Programme, Activity 3.3, funded by the Ministry of Agriculture and Rural Development.