Modeling the dependence of cropping productivity on the hydrothermal coefficient, fertilizer doses, content of mobile forms of phosphorus and potassium in the soil

The article presents the results of 28 years of research with the use of various doses of fertilizers, the patterns of changes in the productivity of crop rotation on soddy-podzolic medium loamy soil of the Vologda region and hydrothermal coefficients (HTC), the content of mobile forms of phosphorus and potassium and their relationship were revealed. Experimental data were formed on the basis of 7 crop rotations (observations over a 28-year period) for five different optimal combinations of nitrogen, phosphorus and potassium (35 observations in total): (1) - 0 kg a.i. fertilizer (control), (2) - N24 P20 K26 kg a.i. fertilizer, (3) - N76 P37 K77 kg a.i. fertilizer, (4) - N93 P33 K92 kg a.i. fertilizer, (5) - N95 P41 K96 kg a.i./ha of fertilizer. The repetition of the experiment is 4-fold, the placement of variants is systematically complicated, the size of the plot is 14m x 10m, the area of the plot is 140 m2, the accounting area for 2-factor studies is at least 24 m2. As research data show, the productivity of crop rotation crops increased with a rise in the doses of applied fertilizers and turned out to be maximum on average for the 1st rotation when using the mineral fertilizer system N93 P33 K92 kg AI/ha (variant 4) and the organomineral fertilizer system - N95 P41 K96 kg a.i. / ha (variant 5), which amounted to 5.7 t/ha of a. unit. The highest productivity turned out to be on average for the 7th rotation of the crop rotation, which corresponded to 7.2-7.4 tons of units/ha in the 4th and 5th variants. In the 2nd - 6th rotations of the crop rotation, variants 4 and 5 were also distinguished - variants with the maximum doses of applied fertilizers. The regression model describing the dependence of crop rotation productivity on HTC, levels of mobile phosphorus and potassium content shows that an increase in the content of mobile forms of phosphorus and potassium in the soil by 1 mg/kg will have a positive effect on crop rotation productivity: with an increase in the content of mobile potassium (X2) by 1 mg/kg of soil at a fixed level of phosphorus content, the productivity of crop rotation increases by an average of 0.0255 t KE/ha; with an increase in mobile phosphorus (X1) by 1 mg/kg of soil at a fixed level of potassium content, crop rotation productivity will also increase by an average of 0.00017 t KE/ha, with an increase in both substances by 1 mg/kg of soil, one can expect productivity growth by an average of 0.0256 t KE/ha.