Cotton yield and boron dynamics affected by cover crops and boron fertilization in a tropical sandy soil

Cover crops may affect diversely boron (B) availability and cotton yield, especially in tropical sandy soils. In turn, B fertilizer rates required by cotton can be dependent on the use of cover crops. This study aimed to evaluate cotton yield, soil-plant B dynamics, and soil fertility as a function of cover crops (fallow, millet, black velvet bean, and millet+ black velvet bean) and B fertilization rates (0, 1, 2, 4, and 6 kg ha(-1)). The experiment was carried out at the field in two crop seasons (2019/2020 and 2020/2021), in Dracena, Sao Paulo State, Brazil. Cover crops increased cotton fiber yields by 47% compared to fallow soil (average two crops), as well as improved B cycling and soil fertility. Proper B rates increased cotton fiber yield by 18%. A maximum cotton fiber yield was reached at 4 kg B ha(-1) (millet + black velvet bean), 2 kg B ha(-1) (black velvet bean) in the 2020/2021 crop season, and 1 kg B ha(-1) in the other system. Critical levels of leaf B ranged from 12 to 16 mg kg(-1). Maximum B uptakes were 182 and 232 g B ha(-1) in the first and second crop seasons, respectively. Boron application and cover crops increased B contents in the soil, but it was below 0.6 mg B dm(-3) in the topsoil. When associated with B fertilization, cover crops, especially the intercropping between millet and black velvet bean, improved soil fertility, plant nutrition, and cotton fiber yields in the tropical sandy soil.

Automated summary

Cover crops have diverse effects on soil fertility, boron cycling, and cotton yields, especially in tropical sandy soils. Proper boron fertilization rates can increase cotton yields, and the optimal rates vary in different cover crop systems.