On-Farm Estimation of Economical and Ecological Optimum Nitrogen Rates for Rice Production: A Field Study of Transplanted Lowland Rice in Central Hills, Nepal

SUMMARYAchieving export growth in rice production from variable rainfed lowland rice ecosystems is at risk if depending on conventional breeding or genetic development alone. Sustained, long-term production requires building adaption capacity of smallholder farmers to better manage the challenges of seasonal climate variability and future climate change. Better understanding of the risks and constraints that farmers face in managing their current cropping system helps develop strategies for improving rice production in Cambodia. System models are now considered valuable assessment tools for evaluating cropping systems performance worldwide but require validation at the local level. This paper presents an evaluation of the APSIM-Oryza model for 15 Cambodian rice varieties under recommended practice. Data from a field experiment in 2011, conducted in a non-limiting water and nutrient environment, are used to calibrate varietal-specific coefficients and model input parameters. An independent dataset is then used to validate the model performance for a ‘real-world’ situation using on-farm data for six rice varieties planted in 54 farmer fields on 32 farms in two villages of Southeastern Cambodia. From this analysis, the APSIM-Oryza model is shown to be an acceptable tool for exploring the mismatch between current on-farm yields and potential production through yield gap analysis and the exploration of cropping system options for smallholder farmers to increase production, adapt to seasonal climate variability and be prepared for potential climate changes.

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High Nitrogen Fertilization Modulates Morpho-Physiological Responses, Yield, and Water Productivity of Lowland Rice under Deficit Irrigation

Agronomy ◽

10.3390/agronomy11071291 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1291

Author(s):

Nasr M. Abdou ◽

Mohamed A. Abdel-Razek ◽

Shimaa A. Abd El-Mageed ◽

Wael M. Semida ◽

Ahmed A. A. Leilah ◽

...

Keyword(s):

Nitrogen Fertilizer ◽

Irrigation Water ◽

Nitrogen Fertilization ◽

Deficit Irrigation ◽

Physiological Responses ◽

Water Productivity ◽

Water Shortage ◽

Rice Production ◽

Lowland Rice ◽

Nitrogen Fertilizers

Sustainability of rice production under flooding conditions has been challenged by water shortage and food demand. Applying higher nitrogen fertilization could be a practical solution to alleviate the deleterious effects of water stress on lowland rice (Oryza sativa L.) in semi-arid conditions. For this purpose, field experiments were conducted during the summer of 2017 and 2018 seasons. These trials were conducted as split-split based on randomized complete blocks design with soil moisture regimes at three levels (120, 100 and 80% of crop evapotranspiration (ETc), nitrogen fertilizers at two levels (N1—165 and N2—200 kg N ha−1) and three lowland Egyptian rice varieties [V1 (Giza178), V2 (Giza177) and V3 (Sakha104)] using three replications. For all varieties, growth (plant height, tillers No, effective tillers no), water status ((relative water content RWC, and membrane stability index, MSI), physiological responses (chlorophyll fluorescence, Relative chlorophyll content (SPAD), and yield were significantly increased with higher addition of nitrogen fertilizer under all water regimes. Variety V1 produced the highest grain yield compared to other varieties and the increases were 38% and 15% compared with V2 and V3, respectively. Increasing nitrogen up to 200 kg N ha−1 (N2) resulted in an increase in grain and straw yields by 12.7 and 18.2%, respectively, compared with N1. The highest irrigation water productivity (IWP) was recorded under I2 (0.89 kg m−3) compared to (0.83 kg m−3) and (0.82 kg m−3) for I1 and I3, respectively. Therefore, the new applied agro-management practice (deficit irrigation and higher nitrogen fertilizer) effectively saved irrigation water input by 50–60% when compared with the traditional cultivation method (flooding system). Hence, the new proposed innovative method for rice cultivation could be a promising strategy for enhancing the sustainability of rice production under water shortage conditions.

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Studies on nitrogenase activity of diazotrophic isolates from different rice production systems

Journal of Applied and Natural Science ◽

10.31018/jans.v8i1.787 ◽

2016 ◽

Vol 8 (1) ◽

pp. 284-289

Author(s):

S. Kanimoli ◽

K. Kumar

Keyword(s):

Acetylene Reduction ◽

Tamil Nadu ◽

Production Systems ◽

Nitrogenase Activity ◽

Rice Production ◽

Lowland Rice ◽

Aerobic Rice ◽

Marked Variation ◽

Reduction Assay ◽

First Time

The present study was carried out to evaluate the nitrogen fixing ability of diazotrophs isolated from the rhizosphere soils of rice which were grown in three different rice growing systems. A total of hundred and ten isolates obtained were subjected to Acetylene Reduction Assay (ARA) and ninety eight isolates recorded significant amount of nitrogenase activity in a range of 185.73 to 3794.55 nmoles of ethylene mg of protein-1 h-1. The highest nitrogenase activity was recorded by Derxia (3794.55 nmoles of ethylene mg of protein-1 h-1) isolated from Trichy (lowland). Among the three different rice production systems, isolates obtained from lowland rice (Derxia â€“ 3794.5 nmoles of ethylene mg of protein-1 h-1) recorded higher nitrogenase activity followed by Aerobic (Pseudomonas - 2194.89 nmoles of ethylene mg of protein-1 h-1) and SRI (Azotobacter - 1971.85 nmoles of ethylene mg of protein-1 h-1) rice isolates. The results revealed marked variation in the ARA of the diazotrophic isolates obtained from lowland, SRI and Aerobic rice. The nitrogenase activity of diazotrophs from rice fields have been reported earlier but the nitrogenase activity of diazotrophs from three different rice production systems from various parts of Tamil Nadu is reported for the first time from India.

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