Can site-specific nutrient management improve the productivity and resource use efficiency of climate-resilient finger millet in calcareous soils in India?

Finger millet, an important 'Nutri-Cereal' and climate-resilient crop, is cultivated as a marginal crop in calcareous soils. Calcareous soils have low organic carbon content, high pH levels, and poor structure. Such a situation leads to poor productivity of the crop. Site-specific nutrient management (SSNM), which focuses on supplying optimum nutrients when a crop is needed, can ensure optimum production and improve the nutrient and energy use efficiency of crops. Moreover, developing an appropriate SSNM technique for this crop could offer new insights into nutrient management practices, particularly for calcareous soils. A field experiment was conducted during the rainy seasons of 2020 and 2021 in calcareous soil at Dr. Rajendra Prasad Central Agricultural University, Pusa, India. The experiment consisted of 8 treatments, viz. control, nitrogen (N)/phosphorus (P)/potassium (K)-omission, 75 %, 100 %, and 125 % recommended fertilizer dose (RFD), and 100 % recommended P and K + 30 kg ha-1 N as basal + rest N as per GreenSeeker readings. From this study, it was observed that the GreenSeeker-based SSNM resulted in the maximum grain yield (2873 kg ha-1), net output energy (96.3 GJ ha-1), and agronomic efficiency of N (30.6 kg kg-1), P (68.9 kg kg-1), and K (68.9 kg kg-1). The application of 125 % RFD resulted in ∼7 % lower yield than that under GreenSeeker-based nutrient management. Approximately 12 % greater energy use efficiency and 21-36 % greater nutrient use efficiency were recorded under GreenSeeker-based nutrient management than under 125 % RDF. The indigenous supplies of N, P, and K were found to be 14.31, 3.00, and 18.51 kg ha-1, respectively. Thus, 100 % of the recommended P and K + 30 kg ha-1 N as basal + rest N according to GreenSeeker readings can improve the yield, nutrient use efficiency, and energy balance of finger millet in calcareous soils.

Environment-friendly nitrogen management practices in wetland paddy cultivation

A large amount of nitrogen (N) fertilizer is required for paddy cultivation, but nitrogen use efficiency (NUE) in paddy farming is low (20–40%). Much of the unutilized N potentially degrades the quality of soil, water, and air and disintegrates the functions of different ecosystems. It is a great challenge to increase NUE and sustain rice production to meet the food demand of the growing population. This review attempted to find out promising N management practices that might increase NUE while reducing the trade-off between rice production and environmental pollution. We collected and collated information on N management practices and associated barriers. A set of existing soil, crop, and fertilizer management strategies can be suggested for increasing NUE, which, however, might not be capable to halve N waste by 2030 as stated in the “Colombo Declaration” by the United Nations Environment Program. Therefore, more efficient N management tools are yet to be developed through research and extension. Awareness-raising campaign among farmers is a must against their misunderstanding that higher N fertilizer provides higher yields. The findings might help policymakers to formulate suitable policies regarding eco-friendly N management strategies for wetland paddy cultivation and ensure better utilization of costly N fertilizer.

Integration of organics in nutrient management for rice-wheat system improves nitrogen use efficiency via favorable soil biological and electrochemical responses

INTRODUCTION

The contrasting soil management in flooded-transplanted rice (Oryza sativa) and dry-tilled wheat (Triticum aestivum) poses a challenge for improving low nitrogen use efficiency (NUE) of the rice-wheat system. Integration of organics in nutrient management can bring in changes favoring efficient N uptake via changes in growing conditions and soil responses.

MATERIALS AND METHODS

This study reported the results of a 15-year-long experiment on integrated nutrient management (INM) systems for rice-wheat cropping. The INM included substituting ~50% of chemical fertilizers via (i) including a legume crop (Vigna radiata) in the sequence and its biomass incorporation (LE), (ii) green manuring with Sesbania aculeata (GM), (iii) farmyard manure application (FYM), (iv) 1/3 wheat stubble in situ retention (WS), and (v) 1/3 rice stubble in situ retention.

RESULTS AND DISCUSSION

The INM strategies resulted in improved NUE compared to 100% chemical fertilizers (F). The INM had significantly higher net N mineralization and improved biological activity aligning with the NUE trends. The reductions in redox potential (Eh) and pH during rice season improved NUE under integrated management. Highly reduced conditions favored N mineralization and plant availability in form of NH 4 + - N resulting in enhanced uptake efficiency, in rice crop. The soil organic carbon (C) significantly increased in INM, and an effect of the active C fractions was evident on the NUE of the wheat crop.

CONCLUSION

The results showed that these INM strategies can immensely benefit the rice-wheat system via improvement in biological health along with electrochemical changes for flooded rice, and labile-C-assisted improvement in soil conditions for wheat.

Demystifying risk attitudes and fertilizer use: A review focusing on the behavioral factors associated with agricultural nitrogen emissions in South Asia

Fertilizer use is environmentally unsustainable in South Asia. Ideally, farmers would follow optimal fertilization rates for crops based on scientific recommendations. However, there is ample evidence on why farmers under-fertilize or over-fertilize their crops. Important amongst them is that farmers' attitude to risk influences decisions on fertilizer use. This paper reviews studies on the effects of risk attitude on fertilizer use, the timing of application, and application intensity. We observe that the use of fertilizer is affected by perceptions of fertilizer as a risk-enhancing or risk-reducing input. In order to influence the future fertilizer decisions of farmers, several policy measures are suggested. Among these, gradual withdrawal of fertilizer subsidies, repurposing subsides toward improved technologies that increase productivity, improves nitrogen use efficiency (NUE) and reduce emission, providing enhanced-efficiency fertilizers and eliminating the fraudulent practice of fertilizer adulteration may be the most appropriate in a South Asian context.

Superior Haplotypes for Early Root Vigor Traits in Rice Under Dry Direct Seeded Low Nitrogen Condition Through Genome Wide Association Mapping

Water and land resources have been aggressively exploited in the recent decades to meet the growing demands for food. The changing climate has prompted rice scientists and farmers of the tropics and subtropics to adopt the direct seeded rice (DSR) system. DSR system of rice cultivation significantly reduces freshwater consumption and labor requirements, while increasing system productivity, resource use efficiency, and reducing greenhouse gas emissions. Early root vigor is an essential trait required in an ideal DSR system of rice cultivation to ensure a good crop stand, adequate uptake of water, nutrients and compete with weeds. The aus subpopulation which is adapted for DSR was evaluated to understand the biology of early root growth under limited nitrogen conditions over two seasons under two-time points (14 and 28 days). The correlation study identified a positive association between shoot dry weight and root dry weight. The genome-wide association study was conducted on root traits of 14 and 28 days with 2 million single-nucleotide polymorphisms (SNPs) using an efficient mixed model. QTLs over a significant threshold of p < 0.0001 and a 10% false discovery rate were selected to identify genes involved in root growth related to root architecture and nutrient acquisition from 97 QTLs. Candidate genes under these QTLs were explored. On chromosome 4, around 30 Mbp are two important peptide transporters (PTR5 and PTR6) involved in mobilizing nitrogen in the root during the early vegetative stage. In addition, several P transporters and expansin genes with superior haplotypes are discussed. A novel QTL from 21.12 to 21.46 Mb on chromosome 7 with two linkage disequilibrium (LD) blocks governing root length at 14 days were identified. The QTLs/candidate genes with superior haplotype for early root vigor reported here could be explored further to develop genotypes for DSR conditions.