Liquid swine manure as a sidedressed nitrogen source for corn

Sidedressing liquid swine (Sus scrofa) manure (LSM) on corn (Zea mays L.) may provide additional time to apply manure and help better match crop-nutrient demand with nutrient supply. A 2-yr, on-farm study was conducted in Minnesota to assess three sidedress nutrient sources—injected LSM via dragline hose, anhydrous ammonia (AA), and urea ammonia nitrate (UAN)—against a non-sidedressed control. At planting, all treatments (including the control) received 46 kg N ha⁻¹ as starter fertilizer. At sidedressing, 157 kg N ha⁻¹ of available N was targeted for application with the different N sources at the fourth leaf collar stage of corn (V4). Sidedressing did not affect plant population compared with the non-sidedressed control in 2018, but sidedressed LSM reduced plant population by 6% relative to the control in 2019, likely due to wet soil conditions and manure injection settings that partially buried plants. In 2018, LSM produced comparable grain yield and net return to sidedressing costs as AA and UAN, despite lower soil ammonium and nitrate levels in the 0- to 15-cm soil layer approximately 12 d after application. In 2019, LSM led to 18–25% lower grain yield than AA and UAN and lower net returns because of a combined plant population reduction and an application of 50 kg plant available N ha⁻¹ less than expected. Sidedressing corn with LSM is a viable alternative to commercial fertilizers, although to realize consistent results, better fine-tuning of application rate, depth, and speed under different soil moisture conditions may be needed.