|YE, RONGZHONG - Clemson University
|PARAJULI, BINAYA - Clemson University
|BAUER, PHILIP - Former ARS Employee
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2020
Publication Date: 4/29/2020
Citation: Ye, R., Parajuli, B., Ducey, T.F., Novak, J.M., Bauer, P.J., Szogi, A.A. 2020. Cover cropping increased phosphorus stocks in surface sandy Ultisols under long-term conservation and conventional tillage. Agronomy Journal. 112(4):3163-3173. https://doi.org/10.1002/agj2.20227.
Interpretive Summary: Phosphorus is an essential plant nutrient but it can create ecological imbalances in surface water bodies when it is at high concentration in runoff from fields. In this study we looked at how conservation tillage and cover crop management practices influence the available and unavailable pools of soil phosphorus. We found that conservation tillage and cover crops promoted the accumulation of surface residue, increasing the inorganic and organic phosphorus pool at the top of the soil surface. Additionally, conservation tillage increased residue accumulation that resulted in higher microbial activity related to phosphorus cycling. These results demonstrate that conservation tillage and cover cropping affect the soils internal phosphorus pools, especially near the soil surface. These findings appear useful for developing phosphorus fertilizer recommendations for conservation tillage and cover crop management systems in sandy soils of the Coastal Plain.
Technical Abstract: Low use-efficiency and high environmental significance of phosphorus (P) requires a better understanding of its stocks and behavior in soils. We investigated P fraction dynamics in sandy Coastal Plain soils, where long-term conservation agriculture driven by conservation tillage and residue return for ~40 years and the integration of cover cropping for four years has been demonstrated to improve soil organic matter (SOM). Soils were collected from fields at 0-5 and 5-15 cm depths to study the effects of tillage (conservation versus conventional) and cover crop (with versus without) on soil stocks of various chemically-defined P pools and the phosphatase potential activities (PHO). Conservation tillage increased potassium chloride-extractable inorganic P (KCl-Pi) stocks in top soils (0-5 cm) when compared to conventional tillage, but had no effects on other pools at both soil depths. Cover cropping caused significant accumulations of sodium hydroxide-extractable organic P (NaOH-Po) in top soils (0-5cm). Nonetheless, neither conservation tillage nor cover crop changed the contributions of the chemically-defined pools to soil total P with NaOH-Po dominating at both soil depths followed by sodium hydroxide-extractable inorganic P (NaOH-Pi) and Hydrochloric-extractable Pi (HCl-Pi). Conservation tillage increased PHO by 128 percent in the 0-5 cm soils, while no cover crop effects were observed. In all, conservation tillage slightly improved P availability potentially through its impacts on microbial activities, while cover cropping increased P stocks and availability by promoting Po accumulations. These findings appear useful for developing phosphorus fertilizer recommendations for conservation tillage and cover crop management systems in sandy soils of the Coastal Plain.