Recharge from precipitation and irrigation
Pumping of large volumes of water from aquifers has occurs each year. If the groundwater is not recharged periodically, the water table fall. Recharge occurs when precipitation is more than required in root zone. The water which enters the soil surface, passes via the root zone, and slowly percolates to the groundwater. In the surrounding area of Koshi River, part of the recharge water move into the aquifer. Even so, the recharge still comes from root zone drainage. Where the water table is declining, recharge occurs during wet periods. When root zone drainage occurs, part of the residual nitrate-N in the root zone is leached out and enters in the groundwater.
Cropping Practices (CP)
Maize production is recognized as a contributor to nitrate contamination of groundwater. In continuous corn production, the soil tends to store organic nitrogen from residues. This organic nitrogen is readily mineralizable,
during the late summer and early fall, when the soil is warm. Mineralization added considerable amounts of mineral nitrogen to the soil after crop uptake is completed. This nitrogen is converted to nitrate and leached in offseason. The research finding has shown that a cornsoybean rotation can cut leaching as compared to continuous corn. Soybean is realised as a scavenger crop that uses residual nitrate-nitrogen in the soil before it fixes its own nitrogen. This reduces the amount of nitrate accessible for leaching during the growing season. Thus the management of water & recommended nitrogen fertilizer practices; result in reduction of nitrate-nitrogen contamination, depending on the soil & irrigation system. Considerably the sprinkler irrigation has the advantage that limited amounts of water can be applied and cause less in-season loss on medium to lighter textured soils.
Precipitation has a huge effect on drainage volume & nitrate losses. It is also affected by dry and wet climatic cycles with greatest losses in wet years. Nitrate losses are highly related to cropping system with row crops yielding greater drainage volumes & nitrate losses. Cover crop reduces nitrate losses. Rate of N application affects nitrate losses more than any other nutrient management. Nitrate losses increase with increasing N rate. The nitrate losses are different among N sources as long as application rate if it is coated with urea or lac while similar Management Practices are followed. Time of application affects nitrate losses but is greatly influenced by temporal distribution of precipitation and source of N. Side dress and late split applications tend to give greater nitrate losses in the succeeding year compared to spring preplant applications. Drainage water management and their depth, influences the volume of drainage and amount of nitrate lost. Nitrate loss, drainage volume, and discharge rate are increased with greater drainage intensity while nitrate and drainage losses are increased with deeper depths. Long-term, subsurface drainage, which integrates the effects of climate variability, soil properties and various cropping systems, is vital to nitrate losses. For more details please contact to:
Dr. AJEET KUMAR
Assistant Professor-cum-Scientist and PI of Nitrate Problem Project in Maize, sanctioned vide O.O. No. 440/IV Res. /DOR/RPCAU, Pusa dated 26.03.2021. Department of Soil Science, SRI, RPCAU, Pusa
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Read more: https://www.rpcau.ac.in/wp-content/uploads/2022/06/F2-A-way-of-Nitrogen-management-to-reduce-nitrate-contamination-in-subsurface-Waters-Ajeet-Kumar2022.pdf
Original link: https://www.rpcau.ac.in/