U.S. Singh

Opportunities for increased nitrogen-use efficiency from improved resource management in irrigated rice systems

Abstract Research and extension work to improve nitrogen (N) management of irrigated rice has received considerable investment because yield levels presently achieved by Asian farmers depend on large amounts of N fertilizer. Most work has focused on placement, form, and timing of applied N to reduce losses from volatilization and denitrification. In contrast, less emphasis has been given to development of methods to adjust N rates in relation to the amount of N supplied by indigenous soil resources. As a result, N fertilizer recommendations are typically made for districts or regions with the implicit assumption that soil N supply is relatively uniform within these domains. Recent studies, however, document tremendous variation in soil N supply among lowland rice fields with similar soil types or in the same field over time. Despite these differences, rice farmers do not adjust applied N rates to account for the wide range in soil N supply, and the resulting imbalance contributes to low N-use efficiency. A model for calculating N-use efficiency is proposed that explicitly accounts for contributions from both indigenous and applied N to plant uptake and yield. We argue that increased N-use efficiency will depend on field-specific N management tactics that are responsive to soil N supply and plant N status. N fertilizer losses are thus considered a symptom of incongruence between N supply and crop demand rather than a driving force of N efficiency. Recent knowledge of process controls on N cycling, microbial populations, and soil organic matter (SOM) formation and decomposition in flooded soils are discussed in relation to N-use efficiency. We conclude that the intrinsic capacity of wetland rice systems to conserve N and the rapid N uptake potential of the rice plant provide opportunities for significant increases in N efficiency by improved management and monitoring of indigenous N resources, straw residues, plant N status, and N fertilizer.

Opportunities for increased nitrogen-use efficiency from improved lowland rice germplasm

Understanding of the mechanisms governing the efficient use of N by rice plants—both its acquisition and internal use—is reviewed. Acquisition efficiency is considered in terms of root properties influencing the absorption and assimilation of NH+4 and other N species, and their regulation; root-induced changes in the rhizosphere affecting N mineralization, transformation and transport; and root-associated biological N2 fixation. Efficiency of internal use is considered in terms of the translocation, distribution and remobilization of absorbed N in different plant organs, flag leaf N import/export and leaf senescence patterns, and the efficiency with which N is used in CO2 fixation. Evidence for genetic variation in both acquisition efficiency and internal-use efficiency is given for plants under N-sufficient and N-limited conditions. The possibility of incorporating in rice the machinery for N2 fixation is discussed.

Grain yield performance of rice genotypes at suboptimal levels of soil N as affected by N uptake and utilization efficiency

Abstract Field screening trials were conducted in two dry seasons to assess variability in grain yield, N uptake and N utilization for 180 rice genotypes, mostly lowland indica improved varieties or elite breeding lines of different growth durations [60 each of early (100–110 days), medium (111–119 days) and late (120–135 days)], without the addition of N fertilizer and to identify genotypes with the potential to produce high yields at suboptimal N levels through efficient uptake and/or utilization of N. Available soil N was lower in year 2 (20 kg ha −1 ) than in year 1 (64 kg ha −1 ). In both years significant differences in grain yield, N uptake and N-utilization efficiency (NUE) were observed among genotypes within each growth-duration group. Genotypes varied in their response to change in available soil N. The average increase in grain yield for each kilogram increase in N uptake was 61.9 kg in year 1 and 82.7 kg in year 2. However, some genotypes absorbed similar amounts of N but produced different grain yields and/or total dry matter. Some genotypes with similar harvest index exhibited significantly different NUEs — e.g., IR50363-61-1-2-2 (NUE = 64.4 in year 1 and 71.9 in year 2) and IR51009-155-2-3-3 (55.3 and 60.8) in the early-duration group; BG380-2 (70 and 78.8) and IR50391-100-2-3-3-2 (56.3 and 58.9) in the medium; and IR27325-63-2-2 (69.7 and 69.8) and BR51-46-1-C1 (57.9 and 60.5) in the late. Those with higher NUE had lower percentage straw N at maturity. Grain N concentration also affected NUE, but the coefficient of variation in percentage grain N among genotypes was less than that of percentage straw N. The relative performance of genotypes in terms of NUE was more consistent than plant N uptake, based on rank correlations between the two trials. High N uptake and NUE were observed in IR13429-150-3-2-1-2 (NUE 65.4, N uptake 9.1 g m −2 ) in the early-duration group, IR44 (NUE 67.2, N uptake 8.3 g m −2 ) in the medium-duration group and IR39323-182-2-3-3-2 (NUE 64.8, N uptake 9.3 g m −2 ) in the late-duration group. The study identified genotypes which may possess promising traits for improved N uptake and utilization efficiency. Further studies are needed to elucidate the mechanisms involved in high N uptake and N-use efficiency.

OPPORTUNITIES TO MANIPULATE NUTRIENT-BY-WATER INTERACTIONS IN RAINFED LOWLAND RICE SYSTEMS

Water stress, accompanied by changes in soil aeration, severely limits rice productivity in rainfed systems. These factors affect nutrient availability. Nitrate (NO3) that accumulates in aerobic soil is rapidly lost through leaching or denitrification in flooded soil. Green manures can act as NO3 catch crops and legumes may gain additional N from biological N fixation. Direct seeding permits additional crops to be grown. Roots are commonly shallow in rainfed lowlands. It is not clear to what extent rice yields in rainfed lowlands are Limited by water, nutrients, and the interactions between them, over diverse soil types, cultural practices and seasonal conditions. Research must determine what really Limits root growth, water extraction and nutrient uptake. Some evidence suggests that manipulation of controlled-release fertilizer and root system development may be the key to optimizing nutrient release and capture in fluctuating environments. The potential for using strategic application of nutrients Co buffer water Limitation and stabilize yields must be examined. Models such as QUEFTS (Quantitative Evaluation of the Fertility of Tropical Soils) provide a potential framework for analyzing the effects of soil fertility and water availability on growth and yield of rice

The drought response of lowland rice to crop establishment practices and N-fertilizer sources

Abstract Increasing drought resistance and nutrient availability to the plant is important for increasing yields in rainfed lowland rice. This study investigated the effects of crop establishment and controlled-release fertilizers on drought stress responses and nitrogen uptake of rice (Oryza sativa L.) cv. PSBRc14 grown on a clayey loam Vertic Tropaquept in a split-split-plot field experiment. The main plots were two water treatments (well-watered and drought-stressed for 20 days from panicle initiation). The subplots comprised of three crop establishment methods. In the sub-subplots, prilled urea was compared with Polyon 12 and POC-S120. Drought prolonged crop maturity by about 20 days and greatly reduced grain yield but not the total biomass and total N uptake. Dry-seeded rice had a lower yield in the well-watered treatment but higher yield in the stress treatment compared with transplanted and wet-seeded rice. The higher yield of dry-seeded rice under stress could be related to its significantly higher root length density, higher root–shoot ratio, and more uniform root distribution with respect to soil depth, and higher available soil moisture in the root zone during the stress period. Under the well-watered condition, yields in all fertilizer treatments were comparable. In the stress treatment, Polyon 12 produced the lowest yield probably because of the mismatch between drought-induced prolongation of crop duration and the release period of Polyon 12.

Addressing sustainability of rice-wheat systems: analysis of long-term experimentation and simulation

The rice-wheat system dominant in the Indogangetic region of South Asia, is facing a number of complex problems, with severe implications on the sustainability of the system. Agronomic, soil, and historical weather data from a long-term experiment (LTE) at Pantnagar, India, were used for analysing yield trends, and in an attempt to explain sustainability related issues for the rice-wheat systems. Validated models (CERES-Rice and CERES-Wheat) were run in sequence using a Sequence Analysis Driver of DSSAT V3.0 for simulating long-term yields of rice and wheat for the LTE. Experimental data indicated that rice yields have declined, whereas wheat yields have increased during the same period. Long-term simulation indicated that, except for some outliers, the yield trends were similar to the trends obtained from the experiment. The Driver was then used in running the rice-wheat experiment for 20 years and 15 replications using generated weather data. The Sequential Analysis Program of DSSAT V3.0 was then used in analysing the trends of model outputs (yields, N, organic C) using percentiles and cumulative probability functions. Yield and soil fertility (total N, organic C) trends in context with sustainability of rice-wheat systems are explained using both long-term experimental and simulation results.

Productivity of sodic soils can be enhanced through the use of salt tolerant rice varieties and proper agronomic practices

Regaining the agricultural potential of sodic soils in the Indo-Gangetic plains necessitates the development of suitable salt tolerant rice varieties to provide an entry for other affordable agronomic and soil manipulation measures. Thus selection of high yielding rice varieties across a range of sodic soils is central. Evaluation of breeding lines through on-station and on-farm farmers’ participatory varietal selection (FPVS) resulted in the identification of a short duration (110–115 days), high yielding and disease resistant salt-tolerant rice genotype ‘CSR-89IR-8’, which was later released as ‘CSR43’ in 2011. Several agronomic traits coupled with good grain quality and market value contributed to commercialization and quick adoption of this variety in the sodic areas of the Indo-Gangetic plains of eastern India. Management practices required for rice production in salt affected soils are evidently different from those in normal soils and practices for a short duration salt tolerant variety differ from those for medium to long duration varieties. Experiments were conducted at the Indian Council of Agricultural Research-Central Soil Salinity Research Institute (ICAR-CSSRI), Regional Research Station, Lucknow, Uttar Pradesh, India during 2011 and 2013 wet seasons, to test the hypothesis that combining matching management practices (Mmp) with an improved genotype would enhance productivity and profitability of rice in sodic soils. Mmp were developed on-station by optimizing existing best management practices (Bmp) recommended for the region to match the requirements of CSR43. The results revealed that transplanting 4 seedlings hill−1 at a spacing of 15 × 20 cm produced significantly higher yield over other treatments. The highest additional net gain was US

Psycho-Biological Changes with Add on Yoga Nidra in Patients withMenstrual Disorders: a Randomized Clinical Trial

3.3 at 90 kg ha−1 N, and the lowest was US

Participatory evaluation guides the development and selection of farmers’ preferred rice varieties for salt- and flood-affected coastal deltas of South and Southeast Asia

0.4 at 150 kg ha−1 N. Above 150 kg ha−1, the additional net gain became negative, indicating decreasing returns from additional N. Hence, 150 kg N ha−1 was considered the economic optimum N application rate for CSR43 in these sodic soils. Using 150–60–40–25 kg N–P2O5–K2O–ZnSO4·7H2O ha−1 in farmers’ fields grown to CSR43 produced an average of 5.5 t ha−1 grain. The results of on-farm evaluation trials of CSR43 showed that matching management practices (Mmp) increased yield by 8% over existing best management practices (Bmp) recommended by ICAR-CSSRI for sodic soils and by 16% over framers’ management practices; however, combining Mmp with CSR43 resulted in 35% higher yields over farmers’ current varieties and management. This approach of combining cost effective crop and nutrient management options and a salt-tolerant variety can maximize the productivity and profitability of sodic soils in the alluvial Indo-Gangetic plains and in neighboring salt-affected areas of the Ganges mega delta in South Asia.

Trichoderma Species as Abiotic Stress Relievers in Plants

Introduction: Menstrual disorders are common problems among women in the reproductive age group. Yuga interventions may decrease the physical and psychological problems related to menstrual disorders. The present study was aimed to assess the effect of Yoga Nidra on psychological problems in patients with menstrual disorders. Methods: A total number of 100 women recruited from the department of obstetrics and gynecology and were then randomly allocated into two groups: a) intervention received yogic intervention and medication for 6 month, and b) control group received no yogic intervention and they only received prescribed medication). Psychological General Well-Being Index (PGWBI) and hormonal profile were assessed at the time of before and after six months on both groups. Results: The mean score of anxiety, depression, positive well-being, general health, and vitality scores, as well as hormonal levels, in posttest were significantly different in intervention group as compared with pretest. But there was no significant difference in control group. Conclusion: Yoga Nidra can be a successful therapy to overcome the psychiatric morbidity associated with menstrual irregularities. Therefore, Yogic relaxation training (Yoga Nidra) could be prescribed as an adjunct to conventional drug therapy for menstrual dysfunction.