Soil Surface Cover on Soybean Cropping Systems Using Technical Uav.

Soil surface cover is an essential characteristic on established no-till systems. It prevents water runoff and soil erosion, also improving nutrient recycle, organic matter accumulation and weed control. We aimed to assess the remaining dry matter on soil surface before sowing soybean and estimate the percentage of soil cover of previous cropping systems in 2015/2016 season using UAV (unnamed aerial vehicles) techniques - a quadcopter with GoPro Hero 4 camera. The systems were: maize (Zea mays); maize intercropped with Urochloa ruziziensis; maize intercropped with Urochloa brizantha; Urochloa ruziziensis; Urochloa brizantha; millet (Pennisetum glaucum); and the association of radish (Raphanus sativus L.) and black oat (Avena strigosa), being harvested and chemically managed before sowing soybean in the spring. Additionally, ammonium nitrate was applied on these fall/winter crops providing 0 and 100 kg ha^-1 of nitrogen (N). The experimental design was randomized blocks with 4 replications, carried out under field conditions in a distroferric Red Nitisol of Itambe, Parana, Brazil. At the time of sowing soybean, an UAV flight was conducted, and the straw dry matter was determined by ground field sampling. The parameters evaluated were influenced only by the cropping systems (P<0.01). The highest values for remaining straw dry matter were obtained by Urochloa ruziziensis and Urochloa brizantha, with 5994.93 kg ha^-1 and 5412.22 kg ha^-1, respectively. However, these systems did not differ from the other ones for the percentage of soil cover. On the other hand, millet had a slight decrease in soil cover (54.79 %), compared to maize (72.32 %), maize with U. ruziziensis (76.21 %) and U. ruziziensis (74.27 %). Also, when comparing the systems including maize, both intercropped ones produced more dry matter than monocrop, evidencing their ability of better protecting the soil in no-till systems.