The effects of intensification on Nitrogen Dynamics and Losses on Diversified Organic Vegetable Farms

Debendra Shrestha1, Krista Jacobsen2, Ole Wendroth3

1University of Kentucky, Ag. Science Bldg. N 308, Lexington, KY, 40546-0091, [email protected] 

2 University of Kentucky, Ag. Science Bldg. N 308, Lexington, KY, 40546-0091

3 University of Kentucky, Ag. Science Bldg. N 1100, Lexington, KY 40546-0091

Abstract

Nitrogen (N) is the main limiting nutrient, and is both a great driver of yield as well as agriculture’s impact on the environment. Organic farming systems are subject to N losses and have less predictable N dynamics than conventional systems. The objective of this study is to compare the N dynamics and key loss pathways in three farming systems, including two organic systems, representing a gradient of intensification (characterized by quantity of inputs, and the frequency of tillage and fallow periods) in Kentucky, USA. We have grown spring planted table beet (Beta vulgaris), summer planted green pepper (Capsicum anuum), and fall planted collard green (Brassica oleracea var. medullosa). Soils were sampled monthly for soil mineral N (NH4+ and NO3-) at 0-15 cm, 15-30, and 30-50 cm depths. Trace gas fluxes (N2O and CO2) were measured weekly using a FTIR-based field gas analyzer. The results of this study showed the higher N2O and CO2 fluxes at the time of fertilizer application and tillage, at the beginning of the crop season.