Low Irrigation Water Improves Biomass Saccharification, Photosynthetic Pigments of Maize, and Minimizes Nitrate Nitrogen Leaching

Nitrogen (N) application under irrigation regimes for improving maize biomass saccharification and reducing soil nitrate (NO3-) losses is an essential agronomic management strategy for sustainable farming. This study aimed to assess the impact of irrigation regimes and N fertilizer dosages on nitrate leaching, plant enzymatic activities, photosynthetic gas exchange, and biomass saccharification of maize straw. Two irrigation water levels such as low irrigation (LW; 60%) and high irrigation (HW; 80%) of field capacity and five N dosages, including 0, 200, 250, 300, and 350 kg N ha(-1), were used as experimental treatments and were replicated four times. A plastic plate was kept below the pot for leachate collection, and it was sampled through a syringe at 10-day intervals. The soil total N, soil mineral N, plant N, soil organic carbon, and plant enzyme activities were also determined. The leaching of NO3- was more (5.36 mg L-1) for 350 kg N ha(-1) under HW compared to other N dosages. The LW decreased NO3- leaching by 10.15%, acid soluble by1.88%, insoluble by 9.69%, and total lignin by 8.72% compared to HW irrigation. In addition, LW irrigation increased grain yield (25.57%), shoot (17.45%), and root dry matter (28.67%) over the HW. The LW irrigation resulted in higher hexoses (21.72% dry matter) and lower acid soluble (2.23% dry matter), acid insoluble (14.32% dry matter), and total lignin content (16.56% dry matter) in N300 treatment. Thus, lowering the N fertilization and irrigation water can be optimally used to prevent NO3- leaching and improve the maize biomass. The application of LW irrigation coupled with low N dose (300 kg ha(-1)) was considered the most optimal rate of irrigation and N fertilizer for increasing maize biomass, enzyme activities, and biomass saccharification, along with potential minimization of NO3- leaching.