| authors: | Alva, A. ; Paramasivam, S. ; Graham, W. ; Wheaton, T.A. |
| title: | Best Nitrogen and Irrigation Management Practices for Citrus Production in Sandy Soils |
| year: | 2003 |
| source: | Water Air & Soil Pollution 143:139-154 |
| URL: | Please log in to access the document. |
| abstract: | Drinking water monitoring data have indicated an increase in nitrate-nitrogen (NO3-N) concentration in groundwater in some parts of the citrus production region of Florida. A proactive, incentive-based program of developing crop-specific best management practices (BMP) began with the Florida N-BMP legislation passed in 1994. A combination of careful irrigation and nitrogen (N) management is needed to improve N uptake efficiency and to minimize potential leaching of nitrate (NO3-N) to the groundwater. An improved N management practice is considered as a BMP, only if that practice is proved to decrease NO3-N leaching into groundwater in commercial groves with out adversely impacting the economics of production. Therefore, long-term evaluation of horticultural responses as well as monitoring groundwater N03-N were conducted in five commercial groves representing different soil types, citrus variety and rootstock, tree age, and cultural practices to determine the impact of changes in N management and/or irrigation scheduling. Groundwater N03-N leaf nutrient concentrations, fruit yield and fruit quality were monitored for 15 months under the grower's routine management and subsequently for 48 months, with improved N and irrigation management practices. The N management practices evaluated in this study included broadcast application of a combination of water soluble and slow release granular products, fertigation, and a combination of foliar application and fertigation. Irrigation was improved by using tensiometer set point of 10 and 15 cbar. This article presents the fruit yield, and concentrations of N, P, K in six-month spring flush during the study period. The study showed that 5 to 8 yr old Valencia trees on Volkamar lemon rootstock produced high quality fruit in the range of 59 to 81 Mg ha?1 with 168 kg N ha?1 as fertigation combined with improved irrigation scheduling. Fruit yield of 36 yr old Valencia orange trees on Rough lemon rootstock was greater with application of 180 kg N ha?1 yr?1 as fertigation compared to that of the trees, which received a similar rate of N as three broadcast applications of granular products. Fertilizer program comprising three foliar applications of N using low biuret urea to deliver 66 kg N ha?1 yr?1 and an additional 76 kg N ha?1 yr?1 as fertigation was the most effective for decreasing surfical groundwater NO3-N while maintaining optimal fruit production and nutritional status of the leaves. The study demonstrated that economically and technically feasible N-BMP's can be developed for citrus grown on sandy soils with a combination of improved N management and irrigation scheduling. |
| keywords: | Fruit quality, groundwater nitrate, nitrogen losses, nitrogen transformation, optimal nitrogen requirement, vadose zone. |
