Study of the dynamics of grass yield within the agricultural landscape based on long-term monitoring
Yield monitoring of a five-component grass stand in a breeding field within a moraine hill was carried out in 2003- 2018 in order to find patterns of its dynamics in the agrolandscape. The grass was used in the conditions of the Tver region without fertilizers in a single-cut mode in a field crossing all microlandscape positions of the hill (transcct) and divided into 30 plots. Annual data on productivity of grass mixture on each plot are presented in the form of: 1) absolute yield (specific hay yield); 2) relative yield (expressed as a percentage to maximum yield on a transect in a definite year). It was revealed that the yield of grasses is maximum in the central parts (≈ 6.5 t/ha) and minimal in the upper parts of the hillsides and at the top (≈ 5.2 t/ha). Time variability of yield depends on the geological structure of the soils - increases with the transition from powerful binomials (≈ 40 %) to low-powerful ones (≈ 65 %). Correlation analysis showed that the transition to relative units (% of the yield) can significantly reduce the impact of climate on data variability. The maximum coincidence of temporal dynamics of different yield indicators is noted at the upper elevations - here climatic conditions do not have a significant impact on the yield, as on slopes. Changes in the sum of the active temperatures have the greatest influence on the yield. Average indicators of correlation coefficients of yield and temperature sums are negative on the plots of soil distribution on powerful and medium-powerful binomials and positive on soils of low-powerful binomials. There has been found an inversely proportional dependence of the absolute yield of grasses on the sums of active temperatures in the pre-cut periods and in September and directly proportional in the second half of summer. Increasing the sum of temperatures contributes to a decrease in relative yields on sandy soils and optimizes the production process on loams and light loams. Dispersion analysis has shown that the main influence of temperatures on absolute yield is exerted by soil hydromorphism. The degree of impact of temperatures on relative yield depends on the nature of water exchange in the agrolandscape, the exposure of slopes (energy) and granulometric composition of soils. The results will make it possible to adapt measures for the placement of grass stands, regulation of water and thermal regimes of soils to farm conditions.