Analysis Of Nitrogen And Phosphorus Losses In Leached And Surface Runoff Water With Application Of Different Fertilizers And Management Strategies Under Typical Crop Rotation System In The Erhai Lake Basin,Yunnan,China

Excessive use of chemical fertilizers resulted non-point source of pollution from agricultural farm land.These non-points source of pollution specifically nitrogen?N?and phosphorus?P?depleted the fresh surface water bodies and underground fresh water aquifers.The same pollutants also depleted the water quality of Erhai Lake in Dali,Yunnan,China.The objective of the study was to protect the water of Erhai Lake from becoming pollutant through addition of N and P as non-point source pollutants from agricultural farm land.To reduce the N&P loading in the surface runoff and leached water a balanced crop nutrition system was practiced with the application of different fertilizer types for typical crop rotation system.Treatments under test designs were;CK?No fertilizers?,CF(Conventional fertilizers practices applied with conventional fertilizers at the rate of 195 Kg N,72 Kg P₂O₅ and 90 Kg K₂O ha^-1),T₁?applied with conventional fertilizer but doses were environment friendly;NPK were 20%lower than CF?,T₂{Refined organic fertilizers?ROF?6500 Kg ha^-1 applied at the rate of 156 Kg N ha^-1},T₃{ROF 2609 Kgha^-1 applied at the rate of 63 Kg N ha^-1,93 Kg N was added through conventional urea?CU?},T₄(ROF 26000 Kgha^-1),T₅{ROF 10436 Kgha^-1applied and 93 Kg N was added through conventional urea},T₆{Controlled release fertilizer?CRF?applied with 20%lower level than CF treatment}.Test design was applied for the rice crop season 2017,broad bean crop season 2017-18 and rice crop season 2018.Leached and surface runoff water samples were collected and tested for total nitrogen?TN?and its forms?NO₃^--N and NH₄⁺-N?,total phosphorus?TP?and soluble active phosphorus?SAP?in the laboratory.Crops were harvested timely and crop yield data was recorded.All the data was analyzed statistically and results were inferred.In case of crop production,for the typical crop rotation cycle Rice-Broad bean-2017-18,CRF?T₆?obtained maximum rice grain yield(9.9 t ha^-1)and broad bean yield(5.1 t ha^-1).The fertilizer improved nitrogen use efficiency?NUE?for the rice crop 2017,broad bean crop season-2017-18 and rice crop season-2018;the NUE recorded was 53%,52%and 53%respectively.The fertilizer reduced 17 to 42%TN and 24 to 41%TP discharge in the leached and surface runoff water during the typical crop rotation system rice-broad bean crop season-2017-18.Similar results were recorded during the rice crop season 2018.Conventional fertilizers applied 20%lower NPK in the treatment T₁ also mitigated the TN discharge in the leached water at 30 cm soil profile depth as compared to CF treatment.The TN recorded declined discharge was 40%,33%for the rice crop season-2017 and 2018respectively.The TN reduced loss in the leached water at 60 cm soil profile depth was 63%and 26%for the rice-broad bean crop season-2017-18 and rice crop season-2018 respectively.Under the mentioned treatment?T₁?TN discharge was also decreased in the surface runoff water and it was 38%and 29%for the rice crop season 2017 and 2018 respectively.Moreover,the treatment also mitigated the NH₄⁺-N,NO₃^--N discharge in the leached and surface runoff water during the both rice crop seasons and during the broad bean crop season as compared to CF treatment.Total phosphorus and SAP losses were also declined under the treatment T₁ as compared to CF.Use of 20%lower conventional fertilizers as compared to CF treatment also promoted the NUE and it was 48%,52%and 50%for the rice crop season 2017,rice-broad bean crop season 2017-18and rice crop season 2018 respectively.Moreover,the mentioned NUE was higher than CF treatment.Similarly,the treatment?T₁?also improved the phosphorus use efficiency?PUE?as compared to CF treatment.Partial application of refined organic fertilizer in combination with CU under the treatment T₅succeeded in achieving the optimum rice grain yield and it was equal to treatment T₁ and not significantly lower than CF treatment.The achieved yield was 7.8,12.3 and 9.8 t.ha^-1 for the rice crop season 2017,rice-broad bean crop season 2017-18 and rice crop season 2018 respectively.The fertilizer mixture also improved the NUE.Total nitrogen losses in the leached water at 30 cm soil profile depth was also reduced as compared to CF treatments and it was 47%and 31%for the rice crop season 2017 and 2018 respectively.In the similar way,TN loss in the leached water at 60 cm was also declined and it was 47%and 32%for the rice-broad bean crop season-2017-18 and rice crop season 2018 respectively.Similarly,TN in the surface runoff water was also declined.Ammonium-N and NO₃^--N were also reduced in the leached and surface runoff water during the both rice crop season.The mixture of fertilizer was also effective in the reduction of TP and SAP losses in the surface and leaching water from the agricultural farm land under paddy rice cultivation.So,it was deduced that both treatments T₁ and T₅ also succeeded in achieving the optimum rice grain yield during the both seasons 2017 and 2918.Application of conventional and refined organic fertilizer mixed with CU at the rate of 20%lower levels than CF treatment was better option for crop production under the rice-broad bean crop rotation system in the Erhai Lake Basin.The former mentioned fertilizer technology not only achieve the optimum yield but also declined the TN and TP losses in the leached and surface runoff water.Among all these fertilizer strategies,the use of CRF was the best option.So,it can be suggested that use of controlled release fertilizer with lower NPK rates has potential to alleviate TN and TP discharge in the leached and surface runoff water from agricultural farm land.Moreover,the fertilizer also could achieve the maximum yield among all the treatments.