Mechanized Hybrid Rice Seed Production: Planting Density, the Flight Height of an Unmanned Aerial Vehicle, Fertilizer Application, and the Row-Ratio of Parents

Abstract

The mechanized seed production of hybrid rice (Oryza sativa L.) represents significant progress in modern agriculture. However, the technologies and the crop management strategies in mechanized hybrid rice seed production are still immature. The present study was conducted with three field experiments to explore the effects of different planting densities, the flight height of an agricultural unmanned aerial vehicle (AUAV) for assisting the pollination, fertilization techniques, and the row-ratio of the restore line and the sterile line on seed yield in hybrid rice seed production. In experiment 1, three planting densities “DS1: 250000 hills per ha; DS2: 285000 hills per ha; DS3: 3,33,000 hills per ha” and three flight heights of an AUAV (FH1: above ground 2 m; FH2: above ground 3 m; FH3: above ground 4 m) were adopted. The results showed that DS1 and DS2 treatments produced a higher seed yield than the DS3 treatment, and the seed yield in the FH2 treatment was significantly higher than FH1 and FH3. In experiment 2, two fertilizer application methods, mechanized deep placement of fertilizer and traditional manual broadcasted fertilizer, were adopted. The results showed that deep placement of fertilizer significantly increased seed yield by increasing the effective panicle number and the grain number per panicle. In experiment 3, three row-ratios of sterile line and restore line at 8:1 (R1), 9:1 (R2), 10:1(R3) were adopted, and the highest seed yield was recorded in the R1 treatment.