Environmental and Agronomic Efficiency of Phosphorus in No-Tillage Corn-Soybean Rotation with Cover Crops.

Nutrient loss, specifically nitrogen and phosphorus, from agricultural systems is a significant contributor to eutrophication and contamination of surface and ground waters. To help protect surface waters, it is vital to have a complete understanding of nutrient cycling in cropping systems and its interactions with nutrient use efficiency and nutrient loss. The objective of this study was to quantify the effects of cover crops and different phosphorus fertilizer management practices on nutrient use efficiency, environmental efficiency and cycling in a no-tillage corn-soybean rotation. This study was conducted in the Central Great Plains (Manhattan, KS) during the 2015-2017 growing seasons on a Smolan Silty clay loam (fine, smectitic, mesic Pachic Argiustoll). Three P management treatments (0 kg P₂O₅/ha, 60 kg P₂O₅/ha broadcast in fall, 60 kg P₂O₅/ha injected sub-surface in spring) and two cover crop treatments (no cover crop and winter cover crop) were arranged in a 3x2 factorial structure applied in 3 replicates to eighteen 0.5 ha plots. Total nutrient uptake, grain removal and yield were measured for each treatment. Results show that total uptake of K₂O (9.4% increase) and recycling of P₂O₅ (23.3% increase) and K₂O (10.3% increase) are directly influenced by cover cropping. Application of P₂O₅ fertilizer also statistically impacted the yield of soybeans during the 2016 growing season. Findings from this study are intended to provide producers with flexible management options for phosphorus fertilizer and cover crops. Data from the 2017 growing season will be presented as available.