Monitoring variability in cash-crop yield caused by previous cultivation of a cover crop under a no-tillage system

Cover crops may be a factor in the variability of soil fertility in areas under a no-tillage system (NTS); one which is not taken into account when fertilising the cash crop. The aim of this work was to evaluate the effect of the variability caused by the dry matter and nutrient cycling of the cover crop on the yield of the succeeding cash crop, by means of the NDVI, calculated by a portable ground sensor and using an unmanned aerial vehicle (UAV). The study was carried out in two areas of a Oxisol cultivated under NTS, where soil samples were taken, for chemical analysis and to evaluate the dry matter and nutrient accumulation in a winter cover crop of black oats. NDVI readings were taken at the R5 and R5.5 stages in soybean. A portable sensor was used seeking a comparison with the readings made by the UAV. It could be seen from the results, that the cover crop has an influence on the main crop under NTS. In the present case, the dry weight of the black oats as well as the accumulated nutrients of nitrogen, phosphorus and magnesium, showed the highest correlations with grain yield in the soybean, whereas for the chemical properties of the soil under evaluation, organic matter had the most influence on the grain yield. The NDVI assessed using the portable ground sensor and with the UAV, was efficient in evaluating the effects of variability in the crop of black oats and in the cycled nutrients.