Applying potassium to ruzigrass prior to cotton reduces the nitrogen requirement and improves yield in a sandy soil under low water availability

Abstract

Nitrogen (N) and potassium (K) are the nutrients most extracted by cotton, and low-fertility sandy soil demands new management strategies to improve fertilization efficiency and yield. The objective of this study was to evaluate the effects of cover crops (fallow, velvet bean, ruzigrass, ruzigrass + velvet bean, inoculated ruzigrass (Azospirillum brasiliensis), and inoculated ruzigrass (Azospirillum brasiliensis) + velvet bean), potassium application timing (pre-planting or post-planting), N rate (80 and 120 kg ha−1) and growing season on cotton yield, yield components, and yield quality. Cover crop dry matter production was higher in the first growing season (2018/2019) than in the second growing season (2019/2020). In the season with the worst climatic scenario (2018/2019), the anticipation K increased number bolls, boll weight and fiber yield under lower application N rates (80 kg ha−1). The inoculated ruzigrass + velvet bean consortium increased fiber yield when 120 kg ha−1 of N was applied at pre-planting K. The fiber quality parameters were influenced by growing season and management. Pre-planting K application increased short fiber content (SFI) with cotton under inoculated ruzigrass. In summary, K application prior to cotton planting in sandy soil in years of rainfall instability enables higher fiber yields under lower N rates (80 kg ha−1), but with regular rainfall K management did not affect cotton yield under inoculated ruzigrass + velvet bean at higher N rate (120 kg ha−1).