Phosphorus drawdown improves net return and water quality in a no-till corn–soybean system

Developing conservation management options that are agronomically and economically feasible, with or without incentivization, and environmentally effective is imperative for reducing phosphorus (P) loss from agricultural fields. A long-term study was established in Northeast Kansas to investigate the effect of P fertilizer management and the use of cover crops on agronomics, economics, and environmental outcomes in a no-till, corn (Zea mays L.)–soybean (Glycine max [L.] Merr.) system. Treatments included two levels of cover crop treatment (with cover crops [CC] and without [NC]) and three levels of P fertilizer management (zero P control [CN], build and drawdown rate management [DD], and build and maintain rate management [MT]). Both DD and MT management increased the cover crop biomass compared to CN. Cover crop treatment reduced corn yield by more than 1,400 kg ha−1 but did not affect soybean yield. Corn yield increased from CN to DD to MT management in a stepwise fashion. Fertilizer treatment effect on soybean yield was mixed, with MT increasing yield significantly in the 2020 soybean crop compared to CN management, but not in the 2022 crop. Consistently, net return was highest for the DD-NC treatment, which also reduced total P loss by 38% and dissolved reactive P loss by 50% in the third year of the study relative to MT-NC. This research illustrates the potential for soil test P drawdown to increase net returns and reduce P losses.