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A field study with varying nitrogen (N) rates (0-150 kg N ha-1) was conducted in Ludhiana (Punjab, India) in a randomized complete block design in three consecutive baby corn seasons to quantify and mitigate N losses to the environment. The nitrous oxide (N2O) flux emissions were measured at 2, 4, 8, 16, and 24 days after each fertilizer N split application. The leachate N losses were estimated by analyzing ammonium and nitrate ion content. Fertilizer N surplus to crop requirement explained 94.1% (spring), 95.9% (summer), and 95.5% (winter) variation in the area-scaled N losses (N2O, leachate). Lower fertilizer N usage by plants at early growth stages (upto V6 stage) resulted in higher N losses within ten days after the first fertilizer application. Carbon equivalent emissions followed the trend summer> spring>winter. Temporal variations during the monitoring seasons influenced the cob and stover yield in response to fertilizer N. On average, 67.9% of the applied fertilizer N was taken up by plants, 4.7% was lost via N leaching, 2.7% escaped as N2O, 3.2% accumulated in the soil profile, and 21.5% remained unaccounted. Sensing-based N application significantly improved N recovery efficiency by 51.2%, mitigated N emissions by 45.4%, and N leaching by 69.3% in comparison with fixed-time blanket fertilizer N topdressings. Fertilizer N management using PAU-LCC provided an economical and farmer-friendly solution to achieve a significant reduction in N losses while sustaining productivity. Further validation and transfer of technology to on-farm locations are needed to benefit from this work. [ABSTRACT FROM AUTHOR]

Fertilizer nitrogen (N) management in long-grained aromatic basmati rice (Oryza sativa) is critical because both below and above the optimum N application rate adversely affects yield. Multi-location field studies were conducted in northwestern India to formulate a site-specific N management (SSNM) strategy for basmati rice by monitoring the greenness of the fully expanded top leaf of the crop plants using a leaf color chart (PAU-LCC) specially developed at Punjab Agricultural University, Ludhiana. The green colour intensity of the successive panels of PAU-LCC increases with consistent decrease in optical reflectance by 1.6% (at 550 nm wavelength) and thus provides better precision in quantifying leaf colour greenness over the IRRI-LCC (the LCC developed at International Rice Research Institute, Philippines). The threshold leaf greenness at which a variety will respond to fertilizer N was found to be equal to LCC shade 3.5 and 4.0 for less and high N responsive varieties, respectively. Monitoring leaf greenness using LCC at weekly intervals and application of 10 kg N ha−1 whenever leaf greenness was less than the specified threshold level constituted the appropriate SSNM strategy. The SSNM produced grain yield equivalent to soil-test-based fixed N rates but with 20 to 60% less N fertilizer. Significantly higher agronomic (average 40.8 vs. 24.5 kg grain kg−1 N) and recovery (average 76.1 vs. 52.7%) efficiencies of fertilizer N were recorded with SSNM than with soil-test-based fixed fertilizer N rates. The SSNM also reduced N2O and GHG emissions by 20.1 and 23.6% as compared to soil-test-based fertilizer N rates. [ABSTRACT FROM AUTHOR]

Site-specific fertilizer nitrogen (N) management using chlorophyll meter (SPAD meter) can help drawing in-season need-based N topdressing decisions. However, SPAD meter based threshold chlorophyll value to trigger supplement N in spring maize is indistinct. Field studies were conducted for two years in sub-tropical and sub-humid climate to study variations in spectral properties and to establish threshold SPAD value for need-based N management in spring maize cultivars. Results specified that N concentration of topmost fully expanded leaf was closely correlated with SPAD meter readings from six-leaf stage (V6) to tasseling stages (VT). The Cate-Nelson plot expressed SPAD 50 as the threshold value to determine plant N need at different growth stages. Need-based topdressings of 30 kg N ha−1, whenever SPAD reading fell below the threshold 50 improved grain yield production by 7.6 to 10.2 per cent over soil test-based N application. SPAD threshold 45 guided N management was inadequate to meet plant N demand, whereas SPAD threshold 55 guided N application lead to N doses in excess of crop requirement without yield benefits. SPAD threshold 50 guided N management ensured better demand-supply synchrony throughout the growth stages and thus reported better N recovery and agronomic efficiencies over soil test-based N management. [ABSTRACT FROM AUTHOR]

Canopy reflectance measurements using active optical sensors have emerged as potential solution to draw in-season nitrogen (N) topdressings in cereals. Site-specific need-based N management strategy using a GreenSeeker optical sensor was developed and evaluated in spring maize. Four field experiments were conducted at two locations during 2017 and 2018 to develop an algorithm, and two experiments during 2019 to validate the sensor-based application for improving N use efficiency (NUE) and grain yield. The sensor measurements made at V9 growth stage with R2 value of 0.61 obtained from the relation between in-season estimate of yield (INSEY) and grain yield rendered better corrective N rate for improving NUE and getting optimum grain yield, whereas sensor measurements at V6, V12 and VT growth stages were not reliable for the purpose. Applying N rate in two splits of 30 kg N ha−1 at planting and 45 kg N ha−1 at V6 growth stage was recommended before applying sensor based corrective N rate at V9 stage. Sensor guided N topdressing produced yields similar to those obtained by following the soil test-based N recommendations but with lower N rates. These results were also reflected in considerable increase in N recovery (8 _18%) and agronomic (4 _13.5 kg grain kg−1 N) efficiencies in comparison with soil test-based N recommendations, thereby signifying the usefulness of the sensor-based algorithm in optimizing need-based fertilizer N management in spring maize. [ABSTRACT FROM AUTHOR]

The present study was conducted to establish prediction models for grain yield and nitrogen (N) uptake using normalized difference vegetation index (NDVI) measurements with the GreenSeeker optical sensor for different cultivar groups of basmati rice (Oryza sativa L.) and to define the optimum sensing timing. Sensor readings were collected at 21, 28, 35, 42, and 49 days after transplanting (DAT) from multi-cultivar and multi-rate N fertilization experiments conducted in 2016 and 2017. Prediction model established by regressing NDVI day−1 as the determinant of plant biomass with grain yield and N uptake at maturity following exponential functions revealed that sensing the crop before or after 35 DAT (panicle initiation stage) was not accurate and did not predict satisfactorily the yield or N uptake potential. Regression analysis generated two potential and viable yield or N uptake prediction models: one for the basmati rice cultivar CSR30 (tall cultivar), and the other for a PB-PUSA (group of semi-dwarf cultivars). Validation of the prediction models using an independent experiment conducted in 2018 revealed that sensing the crop at the panicle initiation stage provide grain yield and N uptake predictions close to the observed grain yield (R2 = 0.86, RMSE = 6.1%) and N uptake (R2 = 0.75, RMSE = 8.5%). This study showed that yield and N uptake potential in basmati rice can be predicted using in-season NDVI data measured with the GreenSeeker optical sensor. [ABSTRACT FROM AUTHOR]

A 4 years field study was conducted to improve nitrogen (N) and phosphorus (P) use efficiencies in wheat (Triticum aestivum L.) using arbuscular mycorrhizal fungi (AMF) and precision N management. Split plot design was employed to rationalize N and P fertilizer use in two different experiments with AMF in the main plot and fertilizer application practice in the subplots. The AMF seed coating improved mycorrhization, root dry weight and P uptake. AMF coating of wheat seeds improved mean grain yield and agronomic efficiency of applied P fertilizer (AEP) by 11% and 55.4%, respectively. However, AMF seed coating did not improve chlorophyll content, normalized difference vegetative index, grain yield and agronomic efficiency of applied N fertilizer (AEN). Precision N management using leaf color chart (LCC), chlorophyll meter (SPAD), and GreenSeeker optical sensor (GS) sustained wheat grain yield equivalent to the soil-test based N fertilizer recommendation with 20–31 kg ha−1 less fertilizer N. Proximal sensing guided N use improved AEN by 21.9%–39.6% while mitigating global warming potential by 16%–24%. Integrated use of AMF seed coating and precision N management provides a potential solution to improve N and P nutrition and reduce environmental footprints of fertilizer N use in wheat. [ABSTRACT FROM AUTHOR]

Background: Excessive application of nitrogen (N) fertilizer in cereal crops not only decreases the N use efficiency but also accelerates greenhouse gas (GHG) emission. Aim: To improve N use efficiency in wheat (Triticum aestivum L.) using precision N management and coating seeds with arbuscular mycorrhizal fungi (AMF). Methods: Field experiment laid out in split‐plot design was conducted to study the role of AMF consortia (four species) seed coating and different precision N management strategies in rationalizing fertilizer N use. Results: The AMF seed coating improved mycorrhization but did not improve N assimilation, grain yield, root weight, N uptake, chlorophyll value, normalized difference vegetative index, and physiological efficiency (PEN) of applied N fertilizer. The benefits of AMF seed coating in improving N assimilation were not visible even in no‐N treatment. Precision N management using leaf color chart (LCC), chlorophyll meter (SPAD), and GreenSeeker optical sensor (GS) sustained wheat grain yield equivalent to the soil‐test based N fertilizer recommendation with the average savings of 20% N fertilizer. Precision N management strategies improved mean recovery efficiency (REN) and partial factor productivity (PFPN) of applied N fertilizer, respectively by 26.0% and 26.4% over the soil‐test based N management. Spectral properties measured with LCC, SPAD and GS showed good correlation (R2 > 0.71) with grain yield, depicting great potential of optical sensing tools in predicting grain yield and inferring need‐based fertilizer N topdressings decisions in wheat. Conclusions: Precision N management provides a potential solution to improve N nutrition in wheat while reducing nitrous oxide (N2O) and total GHG emissions by 23.2 and 23.6%, respectively, in comparison to soil‐test based N application. [ABSTRACT FROM AUTHOR]

Three-year multi-location field experiments were conducted in soils of varying inherent nitrogen (N) supply in diverse agro-climatic zones for improving productivity and mitigating N2O emissions in timely sown and late sown wheat. The biomass, total N uptake (TNU) and spectral properties were monitored at different growth stages. Biomass production and TNU statistics of only 0.76% and 3.4%, respectively, till Zadoks 14 growth stage (four leaves stage) revealed that applying all fertilizer N dose by Zadoks 14 is not an appropriate strategy to assure fertilizer N supply throughout the growth stages. Rescheduled fertilizer N topdressings with moderate N (25 kg ha−1) at sowing and remaining N dose in two equal splits at Zadoks 14 and Zadoks 29 (main shoot and 9 more tillers) growth stages reduced N2O and GHG emissions, respectively, by 32.4% and 30.6%. Sustained N supply till grain filling produced an average of 5.1% to 10.5% higher grain yield and 2.1% to 10.5% higher grain protein content. The spectral properties recorded with PAU-LCC and SPAD meter at Zadoks 29 growth stage governed the grain yield response to fertilizer N application and can be used to fine-tune fertilizer N topdressing decisions over a wide range of varieties, locations, sowing timings and environments. [ABSTRACT FROM AUTHOR]

A 5-year field study was conducted to improve nitrogen (N) and phosphorus (P) use efficiencies in wheat with the synergistic use of plant growth-promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF), and spectral properties for deriving need-based fertilizer N management decisions. Bio-fertilizer consortium inoculation on wheat seed improved rhizosphere mycorrhization, albeit native mycorrhiza also produced mycorrhiza colonization. Lower mycorrhiza colonization was observed in no-P and high P treatments at 30 and 60 days after sowing (DAS) when wheat seeds were not inoculated with bio-fertilizer. However, the mycorrhiza colonization was independent of the fertilizer P level at 60 DAS in the inoculated treatments. The integrated nutrient management with bio-fertilizer and need-based N use sustained highest grain yield with 16.7% and 25% less use of fertilizer N and P, respectively. The agronomic (AE) and recovery efficiencies (RE) of applied N and P were increased by 23.0% (AEN), 21.3% (REN), 40.2% (AEP) and 49.8% (REP), respectively. On-farm validation studies exhibited improvement in partial factor productivity of fertilizer P (PFPP) by 35.8% and fertilizer N (PFPN) by 22.5% in comparison with the soil test-based recommendation. The synergistic use of bio-fertilizer and need-based N management improved the PGPR population, dehydrogenase and alkaline phosphatase activities in soil. The improved soil microbiological properties attributed to better mycorrhization and microflora propagation in soil-facilitated nutrient assimilation and thus higher N and P use efficiencies in wheat. [ABSTRACT FROM AUTHOR]

Tobacco farming is an important economic income in Brazil, although it has been challenged as regard the occupational exposure to both pesticides and nicotine endured by farmers. Chronic occupational exposure to complex mixtures can lead to health hazardous. We examined genomic instability and epigenetic changes in tobacco farmers occupationally exposed to pesticide mixtures and nicotine at tobacco fields. DNA damage was assessed by alkaline comet assay in blood cells. Genomic DNA was isolated, and telomere length was measured using quantitative polymerase chain reaction assay. We measured 5-methyl-2'-deoxycytidine, a marker of global DNA methylation, and p16 promoter methylation. The oxidative profile was evaluated by trolox equivalent antioxidant capacity and lipid peroxidation (thiobarbituric acid reactive substances) in serum. Exposure parameters, plasma cotinine and inorganic element levels, were also measured. DNA damage was significantly elevated for farmers in relation to unexposed group (P < 0.001; Mann-Whitney test) and positively associated with years of exposure. Inverse relationship between DNA damage and total equivalent antioxidant activity was demonstrated for exposed and unexposed groups. Exposed group showed significantly shorter telomeres (P < 0.001; unpaired t-test) and DNA hypomethylation (P < 0.001; unpaired t-test), as well as p16 hypermethylation (P = 0.003; Mann-Whitney test). Lipid peroxidation was increased for exposed group in relation to unexposed one (P = 0.02; Mann-Whitney test) and presented a positive correlation with global DNA methylation (P = 0.0264). Farmers have increased plasma cotinine levels (P < 0.001) and inorganic elements (phosphorus, sulphur and chlorine) in relation to unexposed group. Elevated oxidative stress levels due to chronic occupational pesticide mixtures and nicotine exposure in tobacco farmers were associated with higher DNA damage, shorter telomeres and altered DNA methylation. Telomere-accelerated attrition due to exposure may be potential intermediate step before a disease state. [ABSTRACT FROM AUTHOR]

Blanket fertilizer nitrogen (N) recommendations for large irrigated transplanted rice tracts lead to low N use-efficiency (NUE) due to field-to-field variability in soil N supply and seasonal variability in yield. To achieve high NUE, a fertilizer N management strategy based on visible and near-infrared spectral response from plant canopies using a GreenSeeker™ optical sensor was evaluated. Seven field experiments were conducted during 2005-2007 at two locations in the Indo-Gangetic plains of South Asia to define relationships between in-season sensor measurements at panicle initiation (PI) stage and up to 2 weeks later, and yield of rice. During 2006-2010, seven field experiments were conducted to assess the sensor-based N management strategy and to work out the prescriptive N management to be followed prior to applying sensor-guided fertilizer dose. During 2010 and 2011, the sensor- based N management strategy was evaluated versus farmers' fertilizer practice at 19 on-farm locations. Relationships with R values 0.51 (n = 131), 0.45 (n = 74) and 0.49 (n = 131), respectively, were observed between in-season sensor-based estimates of yield at 42 (PI stage), 49 and 56 days after transplanting of rice and actual grain yield of rice. Applications of 30 kg N ha at transplanting and 45 kg N ha at active tillering stage were found to be the appropriate prescriptive strategy before applying the GreenSeeker-guided dose at PI stage. Sensor-guided N management resulted in similar grain yields as the blanket rate farmer practice, but with reduced N rates, i.e. greater recovery efficiency (by 5.5-21.7 %) and agronomic efficiency [by 4.7-11.7 kg grain (kg N applied)]. This study revealed that high yields coupled with high NUE in transplanted rice can be achieved by replacing blanket fertilizer recommendation by an optical sensor-based N management strategy consisting of applying a moderate amount of fertilizer N at transplanting and enough fertilizer N to meet the high N demand during the period between active tillering and PI before applying a sensor-guided fertilizer N dose at PI stage of rice. [ABSTRACT FROM AUTHOR]

Abstract: Over and untimely application of fertilizer nitrogen (N) are the major constrains in improving fertilizer N recovery efficiency in irrigated wheat (Triticum aestivum L.). Large field to field and seasonal variability further lower fertilizer N recovery efficiency when broad based blanket recommendations are followed. Six field experiments were conducted during 2005 to 2009 at different locations to establish threshold leaf colour greenness to guide in-season need-based fertilizer N topdressings in wheat. Colour of the first top fully exposed leaf as measured by comparison with different shades of green colour on a leaf colour chart (LCC) and wheat grain yield were significantly correlated. The Cate-Nelson plot of leaf greenness expressed as LCC values against relative grain yield of 0.91 indicated that leaf greenness between LCC shade 4 and 5 may guide crop demand driven N applications in wheat. A series of experiments with progressive refinement in treatments were conducted to develop adequate need-based N management strategy using a single threshold LCC value in irrigated wheat. It was found that a dose of at least 25kgNha−1 should be applied at planting. At 1st irrigation (crown root initiation) stage leaf greenness cannot be quantified properly using LCC due to small leaf size and thus it did not lead to adequate fertilizer N management decision. At 2nd irrigation (maximum tillering) stage leaf colour of the first fully exposed leaf served as best indicator of inherent soil N supply as well as crop N needs and thus helped guide need-based fertilizer N top dressing for improving fertilizer N use efficiency in wheat. Fertilizer N management strategy based on application of prescriptive doses of 25kgNha−1 at planting and 45kgNha−1 at 1st irrigation and then a dose of 30 or 45kgNha−1 at 2nd irrigation stage depending on colour of the leaf to be ≥LCC 4 or

Abstract: In the quest of enhancing nitrogen (N) use efficiency in irrigated transplanted rice beyond that observed with blanket recommendation, leaf colour chart (LCC) is being used to apply N whenever colour of the first fully opened leaf from the top is less green than a critical colour shade. So as to avoid frequent (every 7–10 days) monitoring of leaf colour, criteria were developed to apply fertilizer N at critical growth stages of rice but by adjusting the dose of N as per colour of the leaf measured with LCC. A series of experiments were carried out at Ludhiana and Gurdaspur locations from 2007 to 2010 with treatments refined progressively to work out appropriate combination of fixed and adjustable rates of fertilizer N at critical stages of transplanted rice. A dose of 30kgNha−1 at transplanting as prescriptive N management proved to be adequate for achieving high yields of rice. Corrective N management consisting of adjustable N doses was worked out as application of 45, 30 or 0kgNha−1 depending upon leaf colour to be

Abstract: Large field to field variability restricts efficient fertilizer N management when broad based blanket recommendations are used in maize (Zea mays L.). To achieve higher yields and to avoid nitrogen (N) deficiency risks, many farmers apply fertilizer N in excess of crop requirement in maize. Field experiments were conducted for five years (2005–2009) to establish and evaluate threshold leaf colour to guide in-season need based fertilizer N topdressings in four maize genotypes. Colour (of the first top maize leaf with fully exposed collar) as measured by comparison with different shades of green colour on a leaf colour chart (LCC) and maize grain yield was significantly correlated. The Cate–Nelson plot of chlorophyll (SPAD) meter/leaf colour chart values against relative grain yield of 0.93 for the experiments conducted during first two years indicated that LCC shade 5 during vegetative growth stages and LCC shade 5.5 at silking stage (R1) can guide crop demand driven N applications in maize. Evaluation of the established threshold leaf greenness during the next three years revealed that fertilizer N management using LCC 5 starting from six-leaf (V6) stage to before R1 stage resulted in improved agronomic and N recovery efficiency in different maize genotypes. There was no response to fertilizer N application at R1 stage. The study revealed that in maize, fertilizer N can be more efficiently managed by applying fertilizer N dose based on leaf colour as measured by LCC than blanket recommendation. [Copyright &y& Elsevier]

To reduce the amount of wasted reactive nitrogen (N) reaching the environment and to achieve high N fertilizer use efficiency, a site-specific N management strategy using GreenSeeker™ optical sensor (GS) was evaluated in dry direct-seeded rice (DDSR) in the north-western India. Four field experiments were conducted during 2011–2013 to develop an optical sensor algorithm for fine tuning in-season N fertilizer applications. It was demonstrated that panicle initiation of rice is the appropriate stage for applying GS guided N fertilizer dose. Application of a prescriptive dose of 60 kg N ha −1 in two or 90 kg N ha −1 in two or three equal split doses, followed by a corrective N dose guided by GS at panicle initiation stage resulted in rice yield levels comparable to that obtained by following general recommendation, but with lower total N fertilizer application. On an average, N use efficiency was improved by more than 12% when N fertilizer management was guided by GS as compared to when general N fertilizer recommendation was followed. The results prove the inadequacy of general recommendations for N fertilizer management in DDSR and possibility of increasing N use efficiency along with high rice yield levels through site-specific N fertilizer management using GS. [ABSTRACT FROM AUTHOR]

Increasing nitrogen fertilizer applications have sustained a growing world population in the 20th century. However, to avoid any further associated environmental damage, new sustainable agronomic practices together with new cultivars must be developed. To date the concept of nitrogen use efficiency (NUE) has been useful in quantifying the processes of nitrogen uptake and utilization, but we propose a shift in focus to consider nitrogen responsiveness as a more appropriate trait to select varieties with lower nitrogen requirements. We provide a roadmap to integrate the regulation of nitrogen uptake and assimilation into varietal selection and crop breeding programs. The overall goal is to reduce nitrogen inputs by farmers growing crops in contrasting cropping systems around the world, while sustaining yields and reducing greenhouse gas (GHG) emissions. Current practice for managing nitrogen (N) use for cereal production are not environmentally sustainable. Overuse of N fertilizers is a global problem for millions of farmers who must decide on N applications whether, when and how much. A combination of improved advice on N management for specific cropping regimes is required, together with a breeding target of new commercial crop varieties with sustainable yields and a low N requirement. While N use efficiency (NUE) has been a useful concept for quantifying the genetic differences in N uptake and utilization, the concept of an economic N optimum derived from N yield dose–response curves may provide new insights for lowering the N requirement. [ABSTRACT FROM AUTHOR]

Cancer is a leading cause of disease burden throughout the world. Many cancers develop as a result of exposure to both lifestyle and environmental factors that are potentially modifiable. In the last few years, much of the scientific attention has drawn to the discovery of new and effective chemopreventive agents from natural sources. A multitude of phytoconstituents have been explored for their potential to prevent the occurrence of carcinogenesis both in vitro and in vivo by means of diverse cellular and molecular approaches. Key focus of this review is to highlight some significant and new information about different molecular aspects of chemopreventive ability of plant based phytochemicals in terms of their inhibitory potential on cancer growth. In addition, information regarding certain limiting factors such as whole animal physiology, tumour microenvironment and bioavailability of active components of phytoconstituents used in pre/clinical trials are further explored. This review would further assist the scientific community involved in designing efficacious chemopreventive approaches using these phytochemicals in treating cancer. [ABSTRACT FROM AUTHOR]

Wheat is grown on more than 240 million hectares globally, more than any other commercial crop. Variation for nitrogen-use efficiency (NUE) in wheat germplasm is very important as efficiency of nitrogen fertilizers use can have significant effect on overall consumption of N. In the present study we used nested synthetic hexaploid wheat introgression libraries to detect genetic variation associated with NUE and related traits. The libraries were genotyped with 9474 SNP markers and used for genome-wide association mapping. Significant phenotypic variation was observed for all measured and derived traits. We detected 10 Quantitative trait locus (QTL) and 19 marker-trait associations (MTAs) possibly involved in improving NUE. Of these, 5 QTL and 8 MTAs detected under nitrogen-limited conditions have potential for use in breeding to increase nitrogen-deficiency tolerance. Nitrate transporter genes collocated with detected MTAs showed significant changes in expression of TaNRT2 genes in response to N-starvation and N-recovery. The identified promising breeding lines with stable yield, better NUE and acceptable protein content may constitute an important genetic resource in improving NUE of modern wheat varieties. • To meet future wheat production demands, improving nitrogen use while maintaining grain yield is vital. • We identified marker-trait associations improving nitrogen use efficiency while maintaining grain yield under varying nitrogen levels. • We also identified promising breeding lines with significant genetic variations and carrying the trait-associated markers or candidate genes. • These may serve as potential donors to be exploited further in genomics-assisted breeding programs targeting improved NUE while maintaining grain yield in wheat. [ABSTRACT FROM AUTHOR]

Highlights: [•] Optical sensor (GreenSeeker™) and SPAD meter can be used to predict dry direct-seeded rice yield. [•] Predictions made by the LCC are not reliable. [•] Adjusting the LCC scores by CGDD improved the prediction reliability. [ABSTRACT FROM AUTHOR]

Abstract: Large quantities of rice husk ash (RHA), bagasse ash (BA) and coal fly ash (FA) are available in many Asian countries as waste materials, which create a serious disposal problem. Recycling of these ashes on agricultural land can help to improve physical and chemical fertility of soil. The present field experiment was conducted for three and half years to explore the possibilities to utilize these waste materials as soil amendments to improve productivity of rice–wheat system (RWS). The treatments consisted of application of RHA and BA at 10Mgha−1 to either wheat or to rice or to both wheat and rice and 20Mgha−1 to rice alone. The rates used for FA were 15 and 30Mgha−1. Addition of RHA and BA significantly increased the grain yield of wheat and rice but FA caused small increases in crop yields. Direct application of RHA and BA to wheat was significantly superior than their application to rice in the RWS. Direct application of RHA and BA to wheat resulted in 25 and 24% increase in mean grain yield of wheat and 10 and 11% increase in subsequent rice crop, respectively. However, direct application to rice resulted in 8 and 11% yield increase in rice and 10 and 14% increase in subsequent wheat for RHA and BA, respectively. Application of RHA and BA at 20Mgha−1 to rice resulted in lower RWS productivity than that applied at 10Mgha−1 to wheat. There was no significant effect of these ashes on heavy metal contents in grain and straw of the 7th crop of wheat. Application of three types of ashes generally resulted in positive P balance in RWS, however, K balance remained negative. These results suggest that RHA and BA can be recycled successfully in rice–wheat system to improve its productivity with no adverse effect on soil health. [Copyright &y& Elsevier]

Abstract  Poultry litter (PL) is an important nutrient source; however, no information is available regarding its value in supplying N and P in rice–wheat (RW) production. A three-year field study was conducted at Ludhiana, Punjab, India on a loamy sand soil to identify optimum combination of PL and N and P fertilizers for a sustainable RW production. The litter was applied to rice at 5 Mg ha−1 as a single application and supplemented with different rates of N. The residual effect of PL and the direct effects of the different combinations of N and P were studied in the following wheat. Nitrogen and P mineralization from PL was studied under controlled conditions in the laboratory, and macronutrient input–output balances were estimated from field results. About 46% of the N from PL was released after 60 days of incubation. The release of P from the PL occurred mainly during the initial 20 days after incubation, accounting for 15–17% of the total P. Combining PL with fertilizer N (40 kg ha−1) increased rice yield and nutrient uptake similar to what was obtained with the application of recommended fertilizer N (120 kg ha−1). In the following wheat, the residual effect of PL was equal to 30 kg N ha−1 and 13 kg P ha−1. After three annual cropping cycles and PL application, mean soil organic C increased by 17%, Olsen-P by 73%, and NH4OAc-extractable-K by 24%. Most treatments had positive P but negative K balances. About 11% of the net P balance was recovered from the soil as Olsen-P. The study showed that optimum N and P fertilizer doses for an RW system receiving 5 Mg ha−1 of PL are 40 kg N ha−1 for rice and 90 kg N + 13 kg P ha−1 for the following wheat. Safe and effective management of PL should be based on P balance, particularly when regular applications of PL are to be made in the RW system. [ABSTRACT FROM AUTHOR]