Evaluation of NO3-N Leaching in Commercial Fields of Leafy Vegetables by the Soil Nitrogen Balance Estimation System

Nitrate-N (NO3-N) leaching in intensive crop production systems is an important issue due to its potential as a pollutant and a valuable resource. This study aimed at evaluating NO3-N leaching using on-farm measurements and modeling of 12 commercial fields of leafy vegetables characterized by an array of farm management. Real-time monitoring of the soil moisture, temperature and bulk electrical conductivity using a capacitance/resistance sensor was carried out to verify the temperature index and the leaching constant integrated in the soil nitrogen balance estimation system. Results showed that measured soil temperature strongly correlated to model estimates. Values of the leaching constant were 0.0006 kg kg−1 and 0.00075 kg kg−1 (in 2013) both of which were close to the model value of 0.0007 kg kg−1. Values in 2012 were either too high (0.00127 kg kg−1) or too low (0.0010 kg kg−1). NO3-N leaching ranged from 13.50 kg ha−1 to 72.71 kg ha−1 in 2012 and 8.66 kg ha−1 to 41.10 kg ha−1 or 0.00 kg ha−1 to 41.10 with or without rye, respectively. NO3-N leaching in single cropping systems of 2012 was higher than in double cropping systems of 2013.