Irrational Fertilization and Its Impact on Yield and Production Economics
Duško Marinković, PhD, Deputy Manager of the Expert Service of Victoria Logistic
The irrational use of land can significantly reduce or completely destroy its production properties. From the standpoint of quality, the content of organic matter in soil is definitely its most worrying property. Humus content in soil has a significant positive effect on the land’s production properties. Only 51% of agricultural land has a humus content of between 3 and 5%, and just 0.5% of land has a humus content of more than 5%, while 48% of the land used for crop production has a humus content of between 1 and 3%. In the 1960s, the percentage of humus in the soil in Vojvodina was between 4 and 6% for most agricultural land. Over a period of just 50 years, we have reduced the humus content of our land by 1-2%. To bring the humus content back to the level it was at in the 1960s (prior to intensive agricultural production and the mass application of mineral fertilizers alone) would require at least 100 years of putting organic matter back into the soil each year, without exceptions.
Mildly harmful phosphorus content is present on around 18.2% of land or 286,541ha, while extremely harmful to toxic phosphorus content is found on 5.4 and 2.4% of land and/or 58,018 and 39,360ha. This phosphorus content does not originate from our land’s parent substrate (our parent substrate does not actually contain phosphorus), which means that it was introduced by means of uncontrolled mineral and organic fertilizer application. In addition to excess phosphorus in our soil, excess potassium (K) is an even greater issue. 6.0% of the land is optimally fertilized with potassium, while 41.9% is optimally fertilized. The largest portion of land, 43.1%, is fertilized with this nutrient in mild excess. There is a significant excess of potassium on 7.2% of the land and it is toxic/unwanted on 0.6% of the land. Potassium in our soils originates from parent substrate or mineral fertilizers (the famous 15:15:15 combination, regardless of plant species and their nutritional requirements).
The lack of one of these nutrients could easily be solved by ameliorative fertilization. Their excess is more problematic and more difficult to solve. The uncontrolled application of fertilizers, especially on lots where phosphorus and potassium levels are above the optimum, can cause significant damage to cultivated plant yields, as well as the profitability of production. In experiments, sunflower yield, as well as the oil content in seeds, inevitably decreased on the lots where large amounts of potassium were applied, together with increasing doses of N (Table 1).
The results show that the decrease in yield is between 40kg/ha and 550kg/ha when applying irrational amounts of NPK fertilizers. A reduction in oil content of up to 2% is also observed. The application of increased amounts of mineral fertilizers decreases the yield, while simultaneously increasing the investment in the production process. This resulted in multiple losses of between EUR 50 and 241 per ha in production conditions, assuming that the investments in mineral fertilizers in sunflower production are at the level of average investments in the experiment. The effects of improper fertilization with NPK fertilizers on corn yields are shown in Table 2.
In unfavorable years (when there is a lack of precipitation), the application of increased amounts of NPK fertilizers compared to the optimum nutrition decreases the yield. That decrease in yield is between 1.40 and 2.36t/ha of dry seed. Using quantities of fertilizer below the optimum decreases the yield by between 0.84 and 1.40t/ha (variant without fertilization). In the specified years, the application of increased amounts of NPK fertilizers had a greater negative effect on the yield, with the negative financial effects between EUR 298 and 485. Insufficient fertilization resulted in financial loss of between EUR 37 and 130. In favorable years, the losses were greater if fertilization was not optimal and they varied between 2.39 and 4.77t/ha of dry seed. Financial loss was between EUR 318 and 478. Fertilization with excessive amounts of fertilizer resulted in a yield loss of between 0.36 and 1.62t/ha, and financial loss of between EUR 86 and 389.
The data clearly show that over-fertilization results in greater losses in dry years, and vice versa, insufficient fertilization results in greater losses in optimum years.
In order to properly adapt the technology for growing field crops to each field and/or part of it, the soil analyses and field history for that particular field must be obtained. In order to keep a field history with helpful and usable data, an electronic book of fields must be used.
“Za našu zemlju” (“For Our Land”) magazine, No. 49, January 2017