Ecologically-based Agricultural Management Practices Affect Soil Nitrogen Dynamics

The nitrogen (N) conundrum lies in the difficulty farmers face in N provision—soil inorganic N (SIN) is necessary to achieve high yields, but excess SIN is lost through nitrate (NO3-) leaching. Agricultural management systems that synchronize N mineralization from organic amendments with plant uptake will maximize yields while minimizing losses. To understand N dynamics, it is necessary to develop accurate and comprehensive methods to measure N mineralization. This study assessed N mineralization at the Ursinus College Organic Farm in two organic management systems: full tillage with black plastic mulch (BP) and reduced tillage with straw mulch (RT). Using in situ measurements of N mineralization with refinements throughout the study, our results indicate high variability in N transformations in ecologically-based systems. The use of in situ methods provides enhanced understanding of N mineralization in true field conditions, but our data show that refinements are needed to decrease variability and account for multiple N transformation and loss pathways. Our data can be used as a starting ground for further method refinements that will aid the understanding of N mineralization and ultimately confront the N conundrum