Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6363514 | Agricultural Water Management | 2016 | 13 Pages |
Abstract
A 2-year study was conducted to explore the impact of current and alternative best management practices (BMPs) of irrigation and fertigation on nitrate (NO3â) leaching below the root zone. Using a fully randomized complete block design, three fertigation strategies were compared: current BMP with and without accounting for NO3â-N in irrigation-water, and a high frequency fertigation treatment with low-N concentration applications. Temporal changes in water content, pore water NO3â concentrations and soil water potential were monitored within and below the root zone to a soil depth of 3 m at eight sites in an almond and a pistachio orchard. NO3â concentrations below the root zone ranged from <1 mg Lâ1 to more than 2400 mg Lâ1 (almond), and up to 11,000 (pistachio) mg Lâ1, with mean concentrations of 326 and 4631 mg Lâ1, respectively. Within the fertigation cycle, fertilizer injection at the end of an irrigation event generally resulted in lower NO3â losses below the root zone compared with fertilizer injection midway through the irrigation. Pre-bloom and post-harvest flood irrigation in the almond orchard caused deep soil wetting and flushing of NO3â below the root zone, threatening groundwater quality. Statistical analysis using principal component analysis, Chi-squared Automatic Interaction Detector and the Artificial Neural Network showed that most of the deep soil NO3â concentration variability could not be explained by irrigation duration, fertigation timing or local variations in soil physical characteristics. However, mass balance estimates for water and N indicated the annual orchard average N loss could be estimated based on eight monitoring sites in spite of the inherent spatial variations in soil properties and the spatiotemporal variations in water and NO3â applications. The study indicated that reduction of N losses at the orchard scale would require alternative fertigation and irrigation practices, including better control of fertigation amounts and irrigation duration.
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Authors
S. Baram, V. Couvreur, T. Harter, M. Read, P.H. Brown, J.W. Hopmans, D.R. Smart,