Response of Some Soybean Genotypes to Insect Infestation under Three Mineral Nitrogen Fertilizer Rates

Abstract

Background: A two-year study was conducted at Giza Agricultural Research Station, Agricultural Research Center (ARC), Egypt, to evaluate the productivity of six genotypes of soybeans under three mineral nitrogen (N) fertilizer rates, as well as their resistance to insects, in comparison to four check varieties. Methods: The study took place during the 2021 and 2022 summer seasons. The treatments included three mineral N fertilizer rates (N1=67% of N fertilizer rate “71.4 kg N/ha”, N2=33% of N fertilizer rate “35.7 kg N/ha” with seed inoculation by Bradyrhizobium japonicum and N3=100% of N fertilizer rate of the recommended rate “107.1 kg N/ha”) and ten soybean genotypes (H4L4, H6L198, H18L54, H29L115, H129, Misr 10, along with Dr101 and Giza 111 “resistant” and Giza 82 and Crawford “susceptible”). The experiment used a split plot design with three replications. The main plots were assigned the mineral N fertilizer rates, while the subplots, were assigned the soybean genotypes. Result: Fewer cotton leaf worms, whiteflies and leaf miners were found after applying N1 or N2. In the 6th week from sowing, Misr 10 and Dr 101 had fewer cotton leaf worms and whiteflies. In contrast, throughout the 7th, 8th and 9th weeks from sowing, Misr 10 and H6L198 had fewer cotton leaf worms. Misr 10 had fewer leaf miners in every week and fewer whiteflies in the 7th, 8th and 9th weeks from sowing. In the 6th week of the first season, Misr 10, Dr101, H18L54 and Giza 111 that received N1 or N2 had fewer cotton leaf worms; in the 7th and 9th weeks from sowing, Misr 10, Dr101 and H6L198 harbored fewer whiteflies. The lowest pod weight/plant, seed yield/plant, 100-seed weight, seed yield/ha and HI were obtained by using N3. Higher biological yield/ha, seed yield/plant, 100-seed weight, seed yield/ha and HI were attained by Misr 10. In the second season, seed yield per plant and seed yield per hectare were significantly affected by the interaction between soybean genotypes and mineral N fertilizer rates. Growing Misr 10 with 67 per cent N of the recommended rate increased seed yield/plant and seed yield/ha, along with fewer cotton leaf worm, whiteflies and leaf miners compared to the commercial cultivar Giza 111 receiving the recommended mineral N fertilizer rate.