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In Indian semi-arid tropics (SAT) in general and central part i.e. Madhya Pradesh state specifically; there are large yield gaps in most of the rainfed crops between current farmers’ yields and achievable ones. Soil fertility related degradation due to deficiencies of secondary and micronutrients mainly sulphur, boron and zinc in addition to macronutrients is mainly responsible for poor crop productivity, and along with poor hydraulic properties of Vertisols is responsible for about 2 million ha rainy season fallows. Soil health assessment of 11 districts in Madhya Pradesh, India has revealed that in most of the districts only few fields with adequate levels of sulphur, boron, zinc and phosphorus indicating their widespread low levels. Potassium was in general adequate. Farmers’ current blanket fertilization practices focused at macronutrients viz. nitrogen, phosphorus and potassium only, thus does not meet the variable soil fertility needs. Through participatory action research on soil test based fertilizer application, farmers realized benefits in crop productivity to the tune of 5 to 45% in the season of application and additional yield by 5 to 27% due to residual effects of S, B and Zn in succeeding three seasons. An economic assessment showed the balanced nutrition a profitable option in the 1st season itself. In current rainy fallow regions, the landform management as broadbed and furrow or conservation furrow along with balanced nutrition has shown that fallow lands in black soil regions in Madhya Pradesh can be successfully cultivated to grow soybean crop. In succeeding post-rainy season, the rainy season cultivated plots also yielded more as compared to adjoining plots having one crop only in post-rainy season. This study thus found that soil test based fertilization and landform management are the twin technologies for sustainable crop intensification in black soils of Central Indian region.

The inductively coupled plasma (ICP)-based method provides the opportunity to determine phosphorus (P) along with other major, secondary, micro and trace elements in plant materials. This study was conducted to compare and evaluate the relative efficacy of the inductively coupled plasma-optical emission spectrometry (ICP-OES) method with that of the colorimetric method using Skalar autoanalyzer, for determining P in 428 grain samples of eight diverse crops. The results on grain P analysis by the two methods, for individual as well as for all crop samples combined, showed that they were highly positively correlated (r varied from 0.84 to 0.98, p

To determine and characterize the initial background concentrations of heavy metals, a total of 50 sediment samples were collected from the largest lake at the International Crops Research Institute for the Semi-arid Tropics (ICRISAT) in Patancheru, India. The finely ground sediment samples were digested using a microwave-assisted digestion method and analyzed for 15 heavy metals using inductively coupled plasma–optical emission spectrometry (ICP-OES). The results showed that the concentrations of the heavy metals varied greatly with metal and sediment sample, but in general the concentrations were low. Our results suggest that the sediments from this lake (15 ha in area) at the ICRISAT center do not appear contaminated with the heavy metals evaluated, and they indeed reflect normal background concentrations of these metals released through the natural process of weathering.

Drought stress invariably reduces yield and may alter seed chemistry. This experiment was initiated to characterize the sorghum [Sorghum bicolor (L.) Moench] mini core collection for genetic variation and to study the effect of postflowering drought on seed Fe and Zn concentrations. Accessions with similar maturity, together with controls, were evaluated in split-plot design under irrigated and drought-stressed environments for two postrainy seasons. Residual (or restricted) maximum likelihood (REML) analysis of data considering genotypes as random and drought and year as fixed indicated highly significant variance as a result of genotypes. Highly significant effects of drought (D), year (Y), and D x Y interaction emphasized need for multilocation evaluation of germplasm for agronomic and seed nutritional traits. About twofold variation in Fe (25.8–48.9 mg kg−1 seed) and threefold variation in Zn (13.5–42.6 mg kg−1 seed) concentrations was observed across environments. Eleven accessions with high seed Fe, 14 accessions with high Zn, and nine accessions high in both Fe and Zn were identified. These accessions, however, produced low seed yields. In addition, six and four accessions, respectively, showed 8 to 39% and 9 to 38% greater Fe and Zn over control IS 33844 and produced seed yields similar to that of IS 33844. Significant rank correlation (0.70) indicated that accessions with high Fe or Zn under irrigated environments are also expected to perform well under drought-stressed environments. Significantly positive correlation between Fe and Zn indicated simultaneous improvement as a realistic approach in breeding. The identified germplasm are ideal genetic resources for the development of Fe- and Zn-dense sorghum cultivars.

Iron (Fe) deficiency chlorosis in crops is common in high-pH calcareous soils. Soil and plant testing is routinely used for diagnosing iron (Fe) deficiency chlorosis in crops, with mixed results. This article presents an overview of the factors that influence soil and plant tissue testing results. It is clear that soil tests for Fe are dominantly influenced by soil pH, bicarbonate, and moisture regime rather soil test result per se. This is because the solubility of Fe is more regulated by soil pH and moisture regime. Plant tissue testing for Fe can complement the results of soil testing for Fe. But at times, especially in calcareous soils, total Fe in plant tissue is not related to Fe deficiency, but metabolically active Fe is better at diagnosing the occurrence of the disorder. A combined use of soil and plant tissue testing seems more helpful in diagnosing Fe deficiency chlorosis disorder in crops.

The need for analytical support in agricultural research and development has long been recognized, especially for soil fertility evaluation and management, assessment of crop and food quality, and selection and breeding of nutritious food staples. In addition, the demand for analytical research support in the general areas of agriculture interfacing with human health and environmental quality has greatly increased in recent years. The trend for increased demand for analytical support will most likely continue in the future. To meet such diverse, increasing demands for analytical support, we need to upgrade infrastructure facilities and simultaneously teach and train students and young researchers in the use of modern analytical tools. This is prerequisite to providing timely, efficient, and effective analytical support, as such support is the key to monitoring, assessing, and maintaining soil, food, and environmental quality and to breeding nutritious food staples.

Submerging soil creates a series of changes that have important implications for fertility and its management in wetland rice. Wetland rice makes an important contribution to the global rice supply and is often cited as an example of a sustainable production system. We little realize that flooding soil is a powerful driver of changes in fertility and nutrient availability via two most important determinants of soil fertility—pH and redox potential (Eh). The fundamental role of pH in regulating the dynamics of major and micronutrients, toxins, and reduction products in soil solution is well known and used to optimize rice production through management; however, the role of Eh, although equally important, is not appreciated and hence not fully exploited in developing improved fertility management practices. From a synthesis of global literature, this article presents a conceptual framework for the dynamics of soil organic matter and plant nutrients in terms of the combined effects of pH and Eh in submerged ...

Nitrification, the biological oxidation of ammonium to nitrate, weakens the soil's ability to retain N and facilitates N-losses from production agriculture through nitrate-leaching and denitrification. This process has a profound influence on what form of mineral-N is absorbed, used by plants, and retained in the soil, or lost to the environment, which in turn affects N-cycling, N-use efficiency (NUE) and ecosystem health and services. As reactive-N is often the most limiting in natural ecosystems, plants have acquired a range of mechanisms that suppress soil-nitrifier activity to limit N-losses via N-leaching and denitrification. Plants' ability to produce and release nitrification inhibitors from roots and suppress soil-nitrifier activity is termed 'biological nitrification inhibition' (BNI). With recent developments in methodology for in-situ measurement of nitrification inhibition, it is now possible to characterize BNI function in plants. This review assesses the current status of our understanding of the production and release of biological nitrification inhibitors (BNIs) and their potential in improving NUE in agriculture. A suite of genetic, soil and environmental factors regulate BNI activity in plants. BNI-function can be genetically exploited to improve the BNI-capacity of major food- and feed-crops to develop next-generation production systems with reduced nitrification and N2O emission rates to benefit both agriculture and the environment. The feasibility of such an approach is discussed based on the progresses made.

A study was conducted for comparative evaluation of atomic absorption spectrophotometry (AAS) and inductively coupled plasma–optical emission spectroscopy (ICP-OES) for determining extractable zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) in sixty diverse soil samples having a wide range in pH and organic carbon (C). The results were significantly affected by the method of analysis and soil type but generally did not follow a definite trend. Results for extractable Fe in Alfisol samples were significantly greater when using ICP-OES than AAS; and the results for Zn, Cu, and Mn were not significantly different for the two methods. For Vertisol samples, the results for extractable Cu were significantly greater by ICP-OES than by AAS, whereas extractable Fe and Zn were significantly greater by AAS than by ICP-OES, and the results for Mn were not significantly different for the two methods. The results are discussed relative to soil type and differences in soil organic carbon and pH of the samples used...

Meeting the food demands and ensuring nutritional security of the ever increasing global population in the face of degrading natural resource base and impending climate change is the biggest challenge of the twenty first century. The consequences of mineral/micronutrient deficiencies or the hidden hunger in the developing world are indeed alarming and need urgent attention. In addressing the problems associated with mineral/micronutrient deficiency, grain legumes as an integral component of the farming systems in the developing world have to play a crucial role. For resource-poor populations, a strategy based on selecting and/or developing grain legume cultivars with grains denser in micronutrients, by biofortification, seems the most appropriate and attractive approach to address the problem. This is evident from the on-going global research efforts on biofortification to provide nutrient-dense grains for use by the poorest of the poor in the developing countries. Towards this end, rapidly growing genomics technologies hold promise to hasten the progress of breeding nutritious legume crops. In conjunction with the myriad of expansions in genomics, advances in other 'omics' technologies particularly plant ionomics or ionome profiling open up novel opportunities to comprehensively examine the elemental composition and mineral networks of an organism in a rapid and cost-effective manner. These emerging technologies would effectively guide the scientific community to enrich the edible parts of grain legumes with bio-available minerals and enhancers/promoters. We believe that the application of these new-generation tools in turn would provide crop-based solutions to hidden hunger worldwide for achieving global nutritional security.

Aims: As climate change related rainfall and temperature variability is being increasingly experienced in the SAT regions, we assessed climate change mitigation and adaptation potential of Conservation Agriculture (CA) by studying effects of minimum tillage (MT) and residue management practices on rain water use efficiency (RWUE), soil moisture, runoff, energy use and carbon dioxide emission in two maize-legume cropping systems. Study Design: The experiment was laid out in split-split plot design with four replications. Place and Duration of Study: The study was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) farm, Patancheru, Telangana, India during 2010-11 and 2011-12. Methodology: RWUE was calculated as maize equivalent yield divided by rainfall received during the crop season. Integrated digital runoff and soil loss monitoring unit (IDRSMU) was used to measure runoff. Soil moisture content was measured using the gravimetric method (0-30 cm depth) and neutron probe (60-90 cm depth). The soil organic carbon was analyzed following the Walkley-Black method [1]. The diesel consumption in MT and conventional tillage (CT) was estimated following Downs and Hansen (http://www.ext.colostate.edu/pubs) and emission of CO2 was estimated according to EPA, 2009 [2]. Results: Tillage and residue management practices did not show significant effect on RWUE except; CT having significantly higher RWUE over MT during 2011-12. Effect of cropping systems on RWUE was significant but variable during the two years of study. MT-RT (minimum tillage- residue retained) reduced total seasonal runoff by 28.62% and 80.22% compared to CT-RR (conventional tillage- residue removed) in 2010-11 and 2011-12, respectively. Similarly, MT-RT reduced rainwater loss and peak rate of runoff compared to CT-RR in both the years of study. During 2010, MT-RT had higher total soil moisture (v/v) in the 0-90 cm soil depth in sole as well as intercropped maize compared to CT-RR, however, during 2011 MT-RT had higher total soil moisture in sole maize only. As compared to CT, even though, MT improved SOC in 0-15 cm depth but lowered slightly in 15-30 cm depth. RT (residue retained) improved SOC in 0-15 and 15-30 cm depths compared to residue removal (RR). MT-RT had higher or equal SOC in 0-15 and 15-30 cm soil depths compared to CT-RR in both the maize-legume cropping systems. MT saved energy corresponding to 41.49 l of diesel per hectare annually compared to CT. Similarly, MT emitted 110.79 kg less CO2 annually on per hectare basis compared to CT due to reduced diesel use. Conclusion: CA, when adopted by following good agricultural practices and refined to suit the local conditions, could emerge as sustainable production system for climate change mitigation and adaptation of dryland cropping systems in semi-arid tropics of southern India.

Although sweet sorghum is in focus as a promising multi-purpose crop in semi-arid tropical regions, information on optimum nitrogen (N) management remains rather limited. To determine and understand the N dynamics in sweet sorghum-soil ecosystem, we evaluated the N recovery of applied fertilizer in the Alfisol field during the 2009 and 2010 rainy seasons. Sweet sorghum was grown under six N rates (0, 30, 60, 90, 120 and 150 kg N ha-1) with split application (at 0, 30 and 60 days after sowing) and N concentration and N recovery efficiency (NRE) were measured. In addition, to determine the fate of basal and topdressed N, 15N-labeled urea was applied at each application timing within main plots of 90 kg N ha-1. There was no significant difference in NRE calculated by the difference method between six N rates and N uptake rose with increasing N rate. The total dry weight and sugar yield increased at rates up to 90 kg N ha-1 and higher N rates did not significantly affect sorghum productivity. As a total of basal and topdressing applications, 33% of the applied 15N-labeled urea was absorbed by the sorghum plant, while 36 and 30% remained in the soil and unaccounted for, respectively. The NRE calculated by the isotopic method was about 39 and 37% for topdressings at 30 and 60 days after sowing, respectively. The distribution ratio of absorbed N in leaves was higher for basal applications and topdressing at 30 days after sowing, while that in grains was higher for topdressing at 60 days after sowing, compared to the other application timings. In contrast to topdressings, the NRE was very low (13%) for basal N application: about 70% of the basal applied N remained in the soil at the physiological maturity. The results imply that the NRE might be increased by improving the ways in which basal N is applied.

To date, most studies on biological nitrification inhibition (BNI) in sorghum have been performed with plants grown in hydroponic systems. However, the current study was conducted to determine whether or not sorghum inhibits nitrification in fields of Alfisols, and clarify the mechanism that results in inhibition of soil nitrification in the field. Nitrification activity in the rhizosphere of sorghum (Sorghum bicolor (L.) Moench) i.e. soil attached to its roots within a few millimeters was measured and compared with those in adjacent bulk soil. Sweet sorghum (6 varieties) and grain sorghum (3 varieties) were cultivated in 4 Alfisol fields in a semi-arid tropical region of India during the 2010 or 2011 rainy seasons. Soil samples were collected three times during the growing season. Nitrification activity in the rhizospheric soil was significantly lower than that in the bulk soil during 8 out of 12 samplings while the pH (H2O, 1:2) of the rhizospheric soil was significantly lower than that of the bulk soil in 10 out of 12 samplings. Acidification of the soil by sulfuric acid decreased the nitrification activity to a comparable extent, as emerged in the rhizospheric soils. Our results indicate that acidification of soil around roots would be one of the main causes of nitrification inhibition by sorghum in the field.

In the semi-arid tropics (SAT), there exists large yield gaps (two- to four-fold) between current farmers’ yields and achievable yields. Apart from water shortages, soil degradation is responsible for the existing gaps and inefficient utilization of whatever scarce water resource is available. On-farm soil fertility testing across different states in Indian SAT during 2001–2012 showed widespread new deficiencies of sulfur (46–96 percent), boron (56–100 percent), and zinc (18–85 percent) in addition to already known phosphorus (21–74 percent) and nitrogen (11–76 percent, derived from soil carbon). Based on these results, a new fertilizer management strategy was designed to meet varying soil fertility needs at the level of a cluster of villages by applying a full nutrient dose if >50 percent fields were deficient and a half dose in the case of fields

Existing large crop yield gaps between farmers’ fields in rainfed areas and the achievable yields are abridged through integrated watershed management during 2002-2007, while improving farmers’ livelihoods also. In addition to water shortages, emerging widespread deficiencies of multiple micro- and secondary nutrients such as sulphur (S), boron (B) and zinc (Zn) along with nitrogen (N) and phosphorus (P) are holding back the productivity potential through inefficient utilization of limited available water. Soil test-based balanced nutrient application of deficient SBZn plus NP in fields in watersheds recorded 70 to 119% (2100 kg ha −1 in maize, 660 kg ha −1 in groundnut, 640 kg ha −1 in mungbean and 1070 kg ha −1 in sorghum) improvement in crop productivity along with additional returns varying from Rs 16,050/- to Rs 28,160/- ha −1 over the farmers’ practice (only NP). Landform management to alleviate waterlogging proved effective intervention to manage high clay Vertisols for higher soybean and groundnut productivity by 13 to 27% (340 to 350 kg ha −1 in soybean and 160 to 250 kg ha −1 in groundnut) over the farmers’ practice. However, the integrated approach of balanced nutrition and landform management plus improved cultivar was the best option in increasing sunflower productivity by 182% (1600 kg ha −1 in sunflower) over farmers’ management (control). Adoption of these soil-water-crop interventions in target watersheds abridged yield gaps by 12 to 96% in groundnut (160 to 1280 kg ha −1 ), 29 to 100% (240 to 1130 kg ha −1 ) in pigeonpea and 0 to 100% (0 to 1175 kg ha −1 ) in chickpea. The impact of watershed interventions was seen in farm-based activities like improved milk production and incomes. The watershed programs alleviated migration in the catchments by improving the five capitals viz. human, financial, social, physical and natural.

Red ferruginous (RF) soils of tropical Indian environments belong to Entisols, Inceptisols, Alfisols, Mollisols and Ultisols soil orders. The occurrence of Ultisols alongside acidic Alfisols and Mollisols in both zeolitic and non-zeolitic parent materials in humid tropical (HT) climatic environments, indicates that the soil diversity in India is large. These soils are not confined to a single production system and generally maintain a positive organic carbon (OC) balance without adding significantly to greenhouse gas emissions. This review presents a synthesis of literature on the recent developments on the pedology of RF soils, including their physical, chemical, biological, mineralogical and micro-morphological properties, and their degradation status. It also addresses the changes in soil properties in semi-arid tropical (SAT) areas, created by climate shift during the Holocene. This knowledge contributed to our understanding as to how the parent material composition influences the formation of Alfisols, Mollisols and Ultisols in weathering environments of HT climate; and also as to how the relict Alfisols of SAT areas are polygenetic. The state-of-the-art information developed through the extensive work on such soils has helped establish an organic link between pedogenetic processes and bulk soil properties, and has provided an insight of many pedological and edaphological issues related to Alfisols, Mollisols and Ultisols mainly of HT climate. The synthesis has helped us to understand as to why the formation of Oxisols from Ultisols is an improbable genetic pathway in tropical environment of India and elsewhere in the world. There is a strong need to modify the mineralogy class of highly weathered RF soils. We hope this review will help to dispel some of the myths on the formation of tropical soils and their low fertility by putting in context their characteristics and capacity to be productive.

Soil health assessment of farmers’ fields in watershed villages in Medak district, Andhra Pradesh, India showed widespread deficiencies of sulfur (S), boron (B), and zinc (Zn) in addition to organic carbon and phosphorus (P). Participatory on-farm trials on soil test-based application of deficient Zn, B, and S along with nitrogen (N) and P during 2009 to 2012 significantly increased crop yields over farmers’ practice (FP)—by 31% to 45% in chickpea, 15% to 16% in cotton, 12% to 15% in paddy, and 8% to 9% in sugarcane. Total soluble sugars in sugarcane under balanced nutrition (BN) increased by 13%. Residual benefits of S, B, and Zn were observed in succeeding chilly crop (12% higher yield). Benefit to cost (B:C) ratios of BN ranged between 2.8 to 8.5 in chickpea, 2.6 to 4.4 in cotton, 2.3 to 2.9 in paddy, and 7.1 to 11.4 in sugarcane, indicating economic feasibility for scaling-up.

Microbiota in the gut play essential roles in human health. Prebiotics are non-digestible complex carbohydrates that are fermented in the colon, yielding energy and short chain fatty acids, and selectively promote the growth of Bifidobacteria and Lactobacillae in the gastro-intestinal tract. Fructans and inulin are the best-characterized plant prebiotics. Many vegetable, root and tuber crops as well as some fruit crops are the best-known sources of prebiotic carbohydrates, while the prebiotic-rich grain crops include barley, chickpea, lentil, lupin, and wheat. Some prebiotic-rich crop germplasm have been reported in barley, chickpea, lentil, wheat, yacon, and Jerusalem artichoke. A few major quantitative trait loci and gene-based markers associated with high fructan are known in wheat. More targeted search in genebanks using reduced subsets (representing diversity in germplasm) is needed to identify accessions with prebiotic carbohydrates. Transgenic maize, potato and sugarcane with high fructan, with no adverse effects on plant development, have been bred, which suggests that it is feasible to introduce fructan biosynthesis pathways in crops to produce health-imparting prebiotics. Developing prebiotic-rich and super nutritious crops will alleviate the widespread malnutrition and promote human health. A paradigm shift in breeding program is needed to achieve this goal and to ensure that newly-bred crop cultivars are nutritious, safe and health promoting.

Diffuse reflectance spectroscopy (DRS) is a rapid and noninvasive assessment technique for several spectrally active soil properties (chromophores) such as sand, clay, organic C, and Fe contents. The approach is also used for estimating many spectrally inactive constituents (non-chromophores) based on the assumption of covariation between non-chromophores and chromophores. The linkage between covariation and the ability of DRS to estimate a non-chromophore has not been reported in the literature. In this study, we evaluated the covariation assumption using three dependency measures (Pearson correlation coefficient, r; biweight midcorrelation, bicor; and mutual information based adjacency, AMI), five chromophores (organic C, Fe, clay, and sand contents, and geometric mean diameter), and seven non-chromophores (pH, electrical conductivity, P, K, B, Zn, and Al contents) measured in 247 Alfisol and 249 Vertisol samples. An average dependency index (ADI) was developed for each of the three measures (ADIr, ADIbicor, and ADIAMI). The first derivative of the reflectance in conjunction with partial least squares regression was used for data modeling. Model accuracy was evaluated using residual prediction deviation (RPD). The relationships between RPD values of non-chromophores and the ADI values were examined for different chromophore groups (physical, chemical, and combined). The performance of ADIAMI was found to be superior to ADIr and ADIbicor. The ADIAMI computed using chemical chromophores gave strong linear relationships (R2 = 0.93) between ADIAMI and the RPD of chemical non-chromophores, suggesting that the AMI may be used as a robust dependency measure to assess the covariation of non-chromophores with chromophores in DRS.

With environmental issues relating to heavy-metal contamination of natural resources becoming of increasing concern, there is an obvious need to have a method that can be used for routine analysis of a range of materials including soil, sediment, sewage sludge, plant, mineral and organic fertilizers, and other miscellaneous materials for heavy metals of concern. A single-step microwave digestion method was developed using aqua regia solution for digestion of finely ground samples for determining 15 heavy metals in soil, plant, and fertilizer materials using inductively coupled plasma–optical emission spectrometry (ICP-OES). Results on the recoveries of 15 heavy metals added via certified standard reference sample to soil, plant, or fertilizer samples showed that the results varied with the metal and the substrate, and with few exceptions, the results were satisfactory. The method is simple, rapid, and accurate and seems ideal for the routine analyses of a range of materials. Using microwave-assisted diges...

In view of widespread deficiencies, a long-term experiment was started at the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, India in 2007 to identify economically efficient application strategy (full or 50% dose every or every second year) of sulphur (S) (30 kg ha−1), boron (B) (0.5 kg ha−1) and zinc (Zn) (10 kg ha−1). During the fourth year in 2010, balanced fertilization through adding S, B and Zn increased maize grain yield by 13–52% and soybean yield by 16–28% compared to nitrogen (N) and phosphorus (P) fertilization alone. Balanced nutrition increased N and P uptake, utilization and use efficiency for grain yield and harvest index indicating improved grain nutritional quality. The N, P plus 50% of S, B and Zn application every year recorded highest crop yields and N and P efficiencies indices and increased rainwater use efficiency with a benefit:cost ratio of 11.9 for maize and 4.14 for soybean. This study showed the importance of a deficient secondary nutrient S and m...

Thirty-two diverse Jatropha curcas L. cultivars were analyzed for their oil content by the standard Soxhlet extraction method using hexane as solvent. The results were then compared with those obtained by nuclear magnetic resonance (NMR) spectrometer. The cultivars had a wide range in oil content, which ranged from 4.8 to 38.8% by the Soxhlet method and from 6.0 to 38.9% by the NMR method. The values of oil content determined by the NMR method were highly significantly correlated (R2 = 0.9929, P < 0.0001, n = 32) with those obtained using the Soxhlet method. The NMR method is simple, nondestructive, rapid, and accurate for the routine analysis of oil content in Jatropha.

India’s growing self-sufficiency in food production and food stocks since independence suggest that soils have the capacity to produce. Therefore, a review of Indian soils and their capacity to sequester carbon; and the factors favouring C sequestration under different land uses is in order. Several researchers, especially those in The National Bureau of Soil Survey and Land Use Planning and the International Crops Research Institute for Semi-Arid Tropics monitored the changes in soil organic (SOC) and inorganic (SIC) carbon as influenced by land use in the Indo-Gangetic Alluvial Plains and black soil regions between 1980 and 2005. The results showed an increase in SOC stocks due to turnover of greater plant biomass into the soil. Results of long-term fertilizer experiments with rice-based double or triple cropping systems indicate soil’s capacity to store greater C, and maintain higher C in passive pools and that active fraction of soil C can be used as an indicator of soil health. The inclusion of active pool/labile SOC is expected to improve the performance of Century eco-system model in predicting SOC changes under different climatic conditions. Greenhouse gas emissions from the tropical Indian soils (both zeolitic and non-zeolitic) do not seem to contribute significantly to the global warming potential. The application NPK plus FYM emerged as a cost effective technology for Indian farmers. In view of the potential of C sequestration by major zeolitic and non-zeolitic soils, the present SOC stock of about 30 Pg can be further increased.

Internal soil standards are used in an analytical laboratory as one of the tools for providing feedback on the quality of soil-testing service provided. The objective of this study is to provide results on the temporal variability in soil-test values of the internal soil standards used for soil organic carbon and extractable phosphorus (P), potassium, sulfur, boron, and zinc determination in our analytical service laboratory. The range, mean, standard deviation, and coefficient of variation values for the internal standards for various fertility parameters varied according to the parameter and were generally of acceptable quality, except for the extractable P (Olsen P) in the lower range of extractable P. Our results show that the use of internal soil standards in an analytical service laboratory is a simple, inexpensive, and effective tool for providing feedback on the quality of soil-testing service.

Assessment of soil structure and soil aggregation remains a challenging task. Routine methods such as dry- and wet-sieving approaches are generally time consuming and tedious, which calls for a robust, fast, and nondestructive method of soil aggregate characterization. Over the last two decades, diffuse reflectance spectroscopy (DRS) has emerged as a rapid and noninvasive technique for soil characterization. Combined with chemometric and data-mining algorithms, it provides an effective way of measuring several soil attributes and has the added advantage of being amenable to a remote sensing mode of operation. The objective of this study was to determine if the DRS approach could be used as a rapid, noninvasive technique to estimate soil aggregate characteristics. The DRS approach was examined for the estimation of soil aggregate characteristics such as the geometric mean diameter and two statistical parameters of the lognormal aggregate size distribution (ASD) functions using 910 soil samples from India representing three important soil groups. Results showed that the geometric mean diameter and the median aggregate size parameter provided excellent predictions, with ratio of performance deviation (RPD) values ranging from 1.99 to 2.28. The RPD value for the standard deviation of the ASD ranged from 1.36 to 1.72, suggesting moderate prediction. It was further observed that soil aggregates influence the incident electromagnetic radiation on soils primarily in the visible region and to some extent the shortwave- and near-infrared regions. Electronic transitions of Fe-bearing minerals, clay minerals, and C–H functional groups of organic matter may be responsible for modifying the spectral reflectance from soils in addition to the self-shadowing effects of surface roughness. The results of this study suggest that the chemometric approach may be combined with DRS to estimate soil aggregate size characteristics.

Widespread multinutrient deficiencies in the semi-arid tropics (SAT) are among major factors for large gaps between farmers’ current crop yields and potential yields. In this study, we adopted a stratified soil sampling method to assess soil fertility-related constraints in farmers’ fields in eight districts of Andhra Pradesh in the semi-arid tropics of India. Most of the fields across all eight districts were critical in sulfur (61%–98% deficient fields); and up to six districts each in boron (83%–98% deficient fields), zinc (50–85% deficient fields), and soil organic carbon (55–97% deficient fields). Low soil organic carbon specifically indicates nitrogen deficiency. Phosphorus deficiency was critical in three districts (60–84%) while potassium in general was adequate. Soil test-based nutrient balancing through the application of sulfur, boron, and zinc in addition to farmers’ practice of adding only nitrogen, phosphorus, and potassium increased crop productivity by 8%–102%. Benefit–cost ratio (1.60–28.5) proved favourable to scale-up balanced nutrition. Better post-harvest soil health and residual benefits of sulfur, boron, and zinc up to four succeeding seasons indicated sustainability of the practice. Results showed that balanced nutrition is a way forward for sustainably improving farm productivity and livelihoods.

Analysis of soils from 421 farmers’ fields in eastern districts of Rajasthan, India, revealed widespread deficiencies of sulfur (S; 43 to 87% fields deficient), boron (B; 25 to 100%), and zinc (Zn; 0 to 94%) in addition to phosphorus (P; 10 to 73%) and soil organic carbon (1 to 84%). An integrated approach of application of deficient S, B, and Zn along with N and P to high-yielding crop cultivars increased yield over farmers’ practice of N and P application to local cultivars by 92 to 204% in maize, 115 to 167% in pearl millet, and 150% in groundnut. Benefit-to-cost ratio of the integrated strategy varied from 3.33 to 8.03 in maize, 2.92 to 3.40 in pearl millet, and 1.15 in groundnut. The integrated approach effectively utilized scarce water in food production and increased rainwater-use efficiency at 67 to 145 kg mm−1 ha−1 from 21 to 50 kg mm−1 ha−1 under farmers’ practice.

Soil degradation in the semi-arid tropics (SAT) is mainly responsible for low crop and water productivity. In Madhya Pradesh and Rajasthan states in India, the soil analyses of farmers' fields revealed widespread deficiencies of S (9–96%), B (17–100%) and Zn (22–97%) along with that of P (25–92%). Soil organic C was deficient in 7–84% fields indicating specifically N deficiencies and poor soil health in general. During on-farm evaluations in rainy seasons 2010 and 2011, the soil test based addition of deficient nutrient fertilizers as balanced nutrition (BN) increased crop yields by 6–40% (benefit to cost ratios of 0.81–4.28) through enhanced rainwater use efficiency. The integrated nutrient management (INM), however, decreased the use of chemical fertilizers in BN by up to 50% through on-farm produced vermicompost and recorded yields at par or more than BN with far better benefit to cost ratios (2.26–10.2). Soybean grain S and Zn contents improved with INM. Applied S, B, Zn and vermicompost showed residual benefits as increased crop yields for succeeding three seasons. Hence, results showed INM/BN was economically beneficial for producing more food, while leading to resilience building of SAT production systems.

Aim In Alfisols, potassium (K) deficiency limits productivity, as these soils are poor in K-bearing minerals such as mica. As nutrient management practices greatly influence K nutrition of crops especially in the longer term, we evaluated the effects of 27 (1978–2004) years of cropping fingermillet (Eleusine coracana G.) under different manure and mineral fertilizer treatments on K release, balance and yield sustainability on K deficient Alfisols in the semi-arid tropical region of southern India. Methods Fingermillet (variety: PR-202) was grown each year under rainfed conditions with 5 different nutrient management treatments: control (no amendment), 10 Mg ha−1 farm yard manure (FYM), 10 Mg ha−1 FYM +50 % NPK, 10 Mg ha−1 FYM +100 % NPK and 100 % NPK. Potassium release characteristics in the soil profile were determined using 1 N boiling HNO3 (strong extracting solution), 0.01 M HCl (medium extracting solution) and 0.01 M CaCl2 (mild extracting solution). Results Continuous cropping of Alfisols for 27 years resulted in a decrease in K supplying capacity due to soil K depletion through crop K uptake. In soils without K addition, inherent soil supply could not meet the K requirement of fingermillet; thus, a negative K balance following 27 years of cropping affected K nutrition of the crop in all the treatments. As a result, the highest sustainable yield index (SYI) was observed using an integrated nutrient supply (combined application of nutrients from organic and inorganic sources), and the lowest index was obtained without K additions. Conclusion For balanced nutrient management in cereal production systems, K nutrition needs urgent attention in the K deficient Alfisol region of southern India. Addition of any amount of organic manures available at field level offers an alternative strategy for maintaining soil K fertility to improve and sustain crop productivity.

The chlorophyll meter (SPAD-502) is used to estimate nitrogen status of various crops. However, the relationship between SPAD readings and leaf nitrogen concentration (LNC) in sweet sorghum (Sorghum bicolor) has not been fully established. We examined the relationship between SPAD readings and LNC in sweet sorghum in a two-year study; and the effects of leaf thickness on the relationship was also examined. There was a significant relationship between the SPAD reading and LNC at each of two growth stages, but the correlation was weaker when the data for the two growth stages were pooled. This correlation improved when the specific leaf area was introduced as a second independent variable in the multiple regression analysis. This regression equation was applicable to not only different growth stages but also different seasons. The results suggest that the regression equation developed in this study can help in optimizing nitrogen fertilization for sweet sorghum production.

The knowledge on the relationships of protein and micronutrient concentration in wheat grain with edaphic characteristics could provide valuable information for site-specific fertilization of crops for producing grains denser in micronutrients such as iron (Fe) and zinc (Zn) in rain-fed agriculture. In this study, we used soil properties and topographic parameters in the artificial neural network (ANN) methodology as a power tool for improving models for predicting wheat grain micronutrient and protein contents in the hilly regions of western Iran. Soil and grain samples were collected from 1 m2 plots using the stratified random method, whereas the slope positions were considered as the basis of soil sampling, at 100 selected points. The mean grain Zn, Fe, Cu (copper) and Mn (manganese) concentrations were 37.02, 65.86, 14.79 and 44.93 mg–1 kg–1, respectively, and mean grain protein was 13.76%. Application of the ANN models for predicting Zn, Fe, Cu, Mn and protein contents in grains improved prediction b...

Heavy metals are governed by parent material of soils and influenced by the soil physicochemical properties and soil and crop management practices. This paper evaluates total heavy metal concentrations in rainfed soils under diverse management practices of tropical India. Vertisols (clayey soils with high shrink/swell capacity) had the highest concentrations of heavy metals. However, chromium (Cr) content was above the threshold value in Aridisol [calcium carbonate (CaCO3)]-containing soils of the arid environments with subsurface horizon development. Concentration increased at lower depths (>30 cm). Basaltic soils showed higher concentrations of nickel (Ni), copper (Cu) and manganese (Mn). Cadmium (Cd), cobalt (Co), Cu and Mn concentrations were higher in soils cultivated to cotton, whereas Cr concentration was above the threshold level of 110 mg kg−1 in food crop cultivated soils. As the specific soil surface is closely related to clay content and clay type, soil’s ability to retain heavy metals is more closely tied to the specific surface than to the soil cation exchange capacity. Higher positive correlations were found between heavy metal concentrations and clay content [Cd(r = 0.85; p ≤ 0.01); Co (r = 0.88; p ≤ 0.05); Ni (r = 0.87; p ≤ 0.01); Co (r = 0.81; p ≤ 0.05); Zn (r = 0.49; p ≤ 0.01); Cr (r = 0.80; p ≤ 0.05); Mn (r = 0.79; p ≤ 0.01)]. The amounts of nitrogen–phosphorus–potassium applied showed a positive correlation with Co and Ni (r = 0.62; p ≤ 0.05). As several soils used for growing food crops are high in Ni, Cr and Mn, the flow of these metals in soil–plant–livestock/human chain needs further attention.

The aim of this study was to understand the inheritance of grain iron (Fe) and zinc (Zn) concentrations in sorghum [Sorghum bicolor (L.) Moench] and to assess the possibility of exploiting heterosis to improve these micronutrients. Three sets of full diallel crosses were made, one set using five parents contrasting for both grain Fe and Zn concentrations; the second set using six parents contrasting only for Fe, and the third set with four parents contrasting only for Zn. The crosses and parents were evaluated in replicated trials for two years. The results indicated that both additive and non-additive gene action play a role in conditioning grain Fe and Zn concentration in sorghum. However, non-additive gene action is predominant in conditioning grain Fe; and additive gene action in conditioning grain Zn. Some of the crosses showed significant heterosis for grain Fe concentration without yield penalty and some crosses showed targeted grain Zn concentration (40 mg kg−1) coupled with higher grain yields. The results also showed that it is possible to improve grain Fe concentration through exploiting heterosis, but there would be little opportunity if any for improving grain Zn through heterosis breeding. To develop hybrids with high grain Fe and Zn concentration in sorghum both parents needs to be improved for these micronutrients. Combining higher grain Fe and Zn with high yield is feasible.

A study was made to determine the influence of pasture degradation on soil quality indicators that included physical, chemical, biological and micromorphological attributes, along the hillslope positions in Chaharmahal and Bakhtiari province, western Iran. Soil samples from different slope positions were collected from 0 to 30 cm depth for physical and chemical properties and from 0 to 15 cm depth for biological properties at two adjacent sites in the two ecosystems: natural pasture and cultivated land. Soil quality indicators including bulk density, mean weight diameter, soil organic carbon (SOC), particulate organic material (POM) in aggregate fractions, total nitrogen, available potassium, available phosphorus, cation exchange capacity, soil microbial respiration (SMR) and microbial biomass C and N were determined. The results showed that SOC decreased cultivation from 1.09 to 0.77 % following pasture degradation. The POM decreased by about 19.35 % in cultivated soils when compared to natural pasture; also, SMR and microbial biomass C and N decreased significantly following pasture degradation. Furthermore, aggregate stability and pore spaces decreased, and bulk density increased in the cultivated soils. Overall, our results showed that long-term cultivation following pasture degradation led to a decline in soil quality in all selected slope positions at the site studied in the semiarid region.

Rainfed agriculture in the dry regions is affected by water shortages. Our earlier research showed that the deficiencies not only of major nutrients but also those of sulfur (S) and micronutrients are holding back the potential of agricultural production systems. The objectives of this article are to discuss the efficacy of soil testing to diagnose nutrient deficiencies using 28,270 diverse soil samples collected from farmers' fields in the semi-arid tropical (SAT) regions of India and to confirm the efficacy of the soil test-based balanced nutrient management in enhancing productivity of a range of crops in on-farm farmer participatory trials under rainfed conditions. Results of a large numbers of on-farm trials demonstrated that soil testing is indeed an effective tool for on-farm fertility management, a prerequisite for sustainably enhancing the productivity in rainfed areas in the SAT regions of India. The need to strengthen the soil-testing infrastructure in the country is emphasized.

pearl millet ( Pennisetum glaucum (L.) r. Br.) is an important staple food crop in the semiarid tropical regions of Asia and Africa. As part of a major initiative to improve its grain Fe and Zn densities, two sets of line × tester studies were conducted. results showed that the underlying physiological processes determining the grain Fe and Zn densities were largely under additive genetic control, and Fe and Zn densities of the inbred lines per se and their general combining ability (GCA) were positively and highly signifi- cantly correlated. This would imply that recur - rent selection can be effectively used to improve the breeding populations for grain Fe and Zn densities and that breeding lines selected for high Fe and Zn densities per se are more likely to include those with high GCA for these micro - nutrients. Lack of better-parent heterosis indi - cated that to breed hybrids with high Fe and Zn densities would require high levels of these micronutrients in both parental lines. Highly sig - nificant and positive correlations between the Fe and Zn densities, between the GCA of Fe and Zn densities, and between the specific combining ability (SCA) of the Fe and Zn densities showed that simultaneous selection for both micronutri - ents is likely to be effective with respect to all these performance parameters. Consistency in the patterns of results across both sets of trials and across the environments for all the param - eters implies that these results could be of wider application to the genetic improvement of Fe and Zn densities in pearl millet.

Understanding of the hydrological behavior of soils is a prerequisite for developing appropriate soil and water management practices. Such information for Alfisols and Vertisols, the two major soils in the semi-arid tropics (SATs), is scanty especially from a long-term perspective. In this paper, we describe and discuss results from long-term (from 1976 to 2010) hydrological studies conducted on small agricultural watersheds on Vertisols and Alfisols at the ICRISAT Center, Patancheru, India. The hydrological behavior of soils are characterized in terms of runoff volume, peak runoff rate, number of runoff events, soil loss, sediment concentration and deep drainage loss under different rainfall, crop cover and soil moisture conditions to aid in developing effective soil and water management practices. We also provide details on the effects of annual and monthly rainfall on the hydrological behavior of these soils in different rainfall regions. The results show that Alfisols and Vertisols in the SATs have very contrasting hydrological behavior. Several findings emerging from our studies, are rather unexpected. For example, the sandy Alfisols with higher saturated hydrological conductivity generated higher runoff compared to the clayey Vertisols with extremely low saturated hydraulic conductivity. The undesirable early season runoff from Alfisols is higher than from Vertisols. The contribution of 1–2 big storms to annual runoff and soil loss was high on both soils. The contrasting hydrological behavior of these two soils is due to differences in soil characteristics such as crusting, sealing and low structural stability in Alfisols; and the presence of cracks during the early season and formation of micro-cracks during rainless periods in Vertisols. The results suggest that the information from the long-term hydrological studies is useful for determining appropriate soil and water management practices and strategies in different rainfall regions.

Soil depth generally varies in mountainous regions in rather complex ways. Conventional soil survey methods for evaluating the soil depth in mountainous and hilly regions require a lot of time, effort and consequently relatively large budget to perform. This study was conducted to explore the relationships between soil depth and topographic attributes in a hilly region in western Iran. For this, one hundred sampling points were selected using randomly stratified methodology, and considering all geomorphic surfaces including summit, shoulder, backslope, footslope and toeslope; and soil depth was actually measured. Eleven primary and secondary topographic attributes were derived from the digital elevation model (DEM) at the study area. The result of multiple linear regression indicated that slope, wetness index, catchment area and sediment transport index, which were included in the model, could explain about 76 % of total variability in soil depth at the selected site. This proposed approach may be applicable to other hilly regions in the semi-arid areas at a larger scale.

Sweet sorghum is a multipurpose crop that has great potential as a bioethanol crop. To make an appreciable profit from cultivating sweet sorghum in the semi-arid tropics (SAT), such agronomic practices as nutrient management need to be standardized. The objective of this study is to determine optimum nitrogen (N) rates for maximizing the grain and sugar yields of sweet sorghum during the rainy season in the Indian SAT. During the 2009 and 2010 seasons, the response of sweet sorghum being grown in an Alfisol to the application of six N rates (0, 30, 60, 90, 120, and 150 kg N ha-1) was evaluated in Patancheru, Andhra Pradesh, India. The chlorophyll content (SPAD reading), cane fresh weight, and grain dry weight increased significantly in line with higher N rates. The volume of juice also increased significantly, although sugar content (brix reading) did not change in line with higher N rates, consequently resulting in a significant increase in sugar yield as computed from the volume of juice and sugar content. There were smaller differences due to N application during the season when soil fertility was at a medium level under high air temperature. Net income, as estimated from cane fresh weight and grain dry weight, increased at rates up to 90 kg N ha-1, and higher N rates did not significantly affect productivity or income, but instead caused severe lodging in 150 kg N ha-1 at the harvest stage. Based on these results, an input of 90-120 kg N ha-1 could be recommended for maximizing sweet sorghum productivity and farmers’ income in the SAT region of India.

Agriculture is the single largest geo-engineering initiative that humans have initiated on planet Earth, largely through the introduction of unprecedented amounts of reactive nitrogen (N) into ecosystems. A major portion of this reactive N applied as fertilizer leaks into the environment in massive amounts, with cascading negative effects on ecosystem health and function. Natural ecosystems utilize many of the multiple pathways in the N cycle to regulate N flow. In contrast, the massive amounts of N currently applied to agricultural systems cycle primarily through the nitrification pathway, a single inefficient route that channels much of this reactive N into the environment. This is largely due to the rapid nitrifying soil environment of present-day agricultural systems.In this Viewpoint paper, the importance of regulating nitrification as a strategy to minimize N leakage and to improve N-use efficiency (NUE) in agricultural systems is highlighted. The ability to suppress soil nitrification by the release of nitrification inhibitors from plant roots is termed 'biological nitrification inhibition' (BNI), an active plant-mediated natural function that can limit the amount of N cycling via the nitrification pathway. The development of a bioassay using luminescent Nitrosomonas to quantify nitrification inhibitory activity from roots has facilitated the characterization of BNI function. Release of BNIs from roots is a tightly regulated physiological process, with extensive genetic variability found in selected crops and pasture grasses. Here, the current status of understanding of the BNI function is reviewed using Brachiaria forage grasses, wheat and sorghum to illustrate how BNI function can be utilized for achieving low-nitrifying agricultural systems. A fundamental shift towards ammonium (NH4(+))-dominated agricultural systems could be achieved by using crops and pastures with high BNI capacities. When viewed from an agricultural and environmental perspective, the BNI function in plants could potentially have a large influence on biogeochemical cycling and closure of the N loop in crop-livestock systems.

In the mixed crop–livestock systems, while general relation among feed quality, productivity and soil nutrient management have been reported, information on the effects of extractable soil nutrients on crop residue (CR) feed quality traits is scarce (e.g. in semiarid regions of Karnataka, India). In view of the increasingly important role of CR as feed components, in these farming systems, generating such information is a relevant research issue for sustainable development. Here, we report the occurrence and strength of relationships among extractable nutrients in soils and CR feed quality traits, and the effects of improved nutrients input on feed availability and feed quality of CR. Soil samples were collected from farmers’ fields in the semiarid zone of Karnataka and analyzed for available phosphorus (P), potassium (K), sulphur (S), zinc (Zn) and boron (B) using standard laboratory methods. Soil test results were clustered as low, medium or high based on the level of nutrient concentration. Four major farming systems involving nine crops and 419 farms were selected for on-farm trials. Under every sample farm, a plot with farmer’s practice (control) and improved fertilizer inputs (combined application of nutrients found deficient by soil testing) were laid. Performance of crops was recorded. Samples were collected for CR feed quality trait analysis using Near Infrared Reflectance Spectroscopy. The result showed that for cereal and oil crops, extractable soil S was significantly negatively associated with anti-feed quality traits such as neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) (P

The effects of growing Jatropha in on-farm and on-station degraded lands were evaluated on carbon (C) sequestration and soil properties. Jatropha accumulated and added to soil significant amounts of C (305 kg ha−1 year−1) from the year one itself. Overall, a 3–5-year old plantation added per year around 4000 kg plant biomass equivalent to 1450 kg C ha−1 – 800 kg C through leaves, 150 kg C through pruned twigs, and 495 kg C as deoiled Jatropha cake. Biodiesel C replacement in the fossil fuel was 230 kg ha−1. Besides adding biomass to the soil, and C replacement in fossil fuel; the standing Jatropha rendered ecosystem service by fixing 5100–6100 kg ha−1 C as the aboveground plus belowground biomass. Carbon additions by Jatropha during 4 years increased C content in the degraded surface soil layer by 19%, resulting in about 2500 kg ha−1 C sequestered. Huge C additions and live root activity under Jatropha increased microbial population, respiration rate and microbial biomass C and N in soil. Along with C additions, 4000 kg ha−1 year−1 plant biomass recycled into the soil 85.5 kg nitrogen, 7.67 kg phosphorus, 43.9 kg potassium, 5.20 kg sulphur, 0.11 kg boron, 0.12 kg zinc and other nutrients. The C additions improved water holding capacity of the soil under Jatropha as compared with the adjacent control soil which increased by 35% at 30 kPa and 21% at 1500 kPa soil water potential.

Among plant nutrients, nitrogen (N) is the most important. Its importance as a growth- and yield-determining nutrient has led to large and rapid increases in N application rates, but often with poor use efficiency. Nitrogen management requires special attention in its use so that the large losses can be minimized and the efficiency maximized. Site-specific nutrient management (SSNM) has been found especially useful to achieve the goals of improved productivity and higher N use efficiency (NUE). Leaf color charts and chlorophyll meters assist in the prediction of crop N needs for rice and wheat, leading to greater N-fertilizer efficiency at various yield levels. Crop simulation models can be used in combination with field information and actual weather data to make recommendations to achieve higher NUE. Remote sensing tools are also used to predict crop N demands precisely. At the same time, traditional techniques like balanced fertilization, integrated N management (INM), use of nitrification inhibitors a...

The ability to suppress soil nitrification through the release of nitrification inhibitors from plant roots is termed ‘biological nitrification inhibition’ (BNI). Here, we aimed at the quantification and characterization of the BNI function in sorghum that includes inhibitor production, their chemical identity, functionality and factors regulating their release. Sorghum was grown in solution culture and root exudate was collected using aerated NH4Cl solutions. A bioluminescence assay using recombinant Nitrosomonas europaea was employed to determine the BNI activity. Activity-guided chromatographic fractionation was used to isolate biological nitrification inhibitors (BNIs). The chemical structure was analyzed using NMR and mass spectrometry; pH-stat systems were deployed to analyze the role of rhizosphere pH on BNIs release. Sorghum roots released two categories of BNIs: hydrophilic- and hydrophobic-BNIs. The release rates for hydrophilic- and hydrophobic- BNIs ranged from 10 to 25 ATU g−1 root dwt. d−1. Addition of hydrophilic BNIs (10 ATU g−1 soil) significantly inhibited soil nitrification (40 % inhibition) during a 30-d incubation test. Two BNI compounds isolated are: sakuranetin (ED80 0.6 μM; isolated from hydrophilic-BNIs fraction) and sorgoleone (ED80 13.0 μM; isolated from hydrophobic-BNIs fraction), which inhibited Nitrosomonas by blocking AMO and HAO enzymatic pathways. The BNIs release required the presence of NH 4 + in the root environment and the stimulatory effect of NH 4 + lasted 24 h. Unlike the hydrophobic-BNIs, the release of hydrophilic-BNIs declined at a rhizosphere pH >5.0; nearly 80 % of hydrophilic-BNI release was suppressed at pH ≥7.0. The released hydrophilic-BNIs were functionally stable within a pH range of 5.0 to 9.0. Sakuranetin showed a stronger inhibitory activity (ED50 0.2 μM) than methyl 3-(4-hydroxyphenyl) propionate (MHPP) (ED50 100 μM) (isolated from hydrophilic-BNIs fraction) in the in vitro culture-bioassay, but the activity was non-functional and ineffective in the soil-assay. There is an urgent need to identify sorghum genetic stocks with high potential to release functional-BNIs for suppressing nitrification and to improve nitrogen use efficiency in sorghum-based production systems.

The continuous growing of rice has led to a deterioration in soil quality, resulting in a serious threat to agricultural sustainability in the high rainfall zone of south Gujarat, India. Therefore, crop diversification with a wider choice in the production of crop varieties is being promoted to restore the soil quality. A field experiment was conducted in Navsari, India during 2003–2007 on a Vertisol to evaluate the productivity, sustainability, resource-use efficiency and economics of 10 rice-based cropping systems. The results showed that system productivity for rice–fenugreek (Trigonella foenum-graecum)–okra (Abelmoschus esculentus) was highest (25.73 t ha−1), followed by rice–onion (Allium cepa)–cowpea (Vigna sinensis L.) (24.15 t ha−1); and the lowest system productivity was observed with the rice–wheat (Triticum aestivum)–fallow system (7.85 t ha−1). The sustainable yield index (0.97), production efficiency (102.94 kg ha−1 day−1) and field water use efficiency (15.98 kg ha−1 mm−1) were maximum with ...

Soil nutrient contents were determined in 802 surface soil samples (0–15 cm deep) collected from farmers' fields that support extensive cultivation of soybean (Glycine max L.) and finger millet (Eleusine coracana G.), spread across three districts, in the semi-arid regions of Karnataka, India. Following soil analysis, on-farm crop trials were conducted during 2005–2007 to study the crop response to the soil application of nitrogen (N), phosphorus (P), sulfur (S), boron (B), and zinc (Zn) fertilizers. Analyses of soil samples revealed that 4–83% fields were deficient in N, 34–65% in P, 83–93% in extractable S, 53–96% in B, and 34–88% of farmers' fields were deficient in Zn. On-farm trials conducted during the three rainy seasons (2005, 2006, and 2007) significantly (P ≤ 0.05) enhanced crop productivity indices such as yields of grain, stover, and total biomass in soybean and finger millet crops. Integrated management of deficient nutrients in finger millet and soybean crops significantly enhanced the grain...

The lowland rice system in Asia makes a major contribution to the global rice supply and is often cited as an example of a sustainable system in which two or three crops of rice are grown in sequence under submerged conditions. However, water shortages are becoming critical in some regions for lowland rice cultivation; and there is high potential in exploring rice cultivation under moisture regimes that save water and also increase productivity. The objective of this article therefore is to analyze the consequences of switching growing of rice from flooded to aerobic conditions on soil fertility and its management. Fertility advantages of submerged rice include amelioration of chemical fertility, preferential accumulation of organic matter and improved availability of major, secondary and selected micronutrients, which contribute to the long-term maintenance of soil fertility and sustainability of the lowland rice system. However, the fertility problems under aerobic rice are better addressed with the cro...

Frequency of boron (B) deficiency is increasing in rainfed systems, and hence there is a need to diagnose the deficiency. Colorimetric methods are still widely used in soil-testing laboratories in India for measuring B. Little information is available on the comparative evaluation of the colorimetric and inductively coupled plasma (ICP) methods for determining extractable B in soils. We describe results of the comparative evaluation of these methods for measuring extractable B in 57 soil samples with pH values ranging from 5.3 to 9.5. There was a significant correlation between B values determined by the two methods, and the correlation coefficient was greater for soil samples with pH in the neutral to alkaline range. Interaction between soil samples and methods (ICP or colorimetric) was significant except for soil samples in the pH range of 8.0 to 9.5. Precision for B determination was greater with the ICP than with the colorimetric method.

Foxtail millet is an important staple crop in some parts of China, India and Japan, and a potential bioenergy source. The grains are rich source of protein, fiber, minerals and vitamins. We had earlier reported the development of a core collection (155 accessions) of foxtail millet. This study was initiated to identify trait-specific germplasm for agronomic and nutritional traits, and to develop a mini core through multilocational evaluation of the foxtail millet core collection. One hundred and fifty-five accessions together with five controls (four common and one location-specific control) were evaluated for 21 descriptors at five agro-ecologically diverse locations in India during the 2008 rainy season. The experiment was conducted in an alpha design with three replications at Patancheru, and in an augmented design with one of the five controls repeated after every nine-test entries at other locations. A number of diverse germplasm accessions with agronomically (earliness and high grain yield) and nutritionally (high seed protein, calcium, iron and zinc) superior traits were identified for use in foxtail millet breeding. The hierarchical cluster analysis of data using phenotypic distances resulted in 25 clusters, from each cluster, ∼10% or a minimum of one accession was selected to form a mini core, which comprised of 35 accessions. The comparison of mean, variance, frequency distribution, diversity (H’) and phenotypic correlations revealed that the mini core indeed captured adequate variability from the core collection. This mini core collection is an ideal pool of diverse germplasm for studying population structure and diversity, and identifying new sources of variation for use in breeding and genomics studies in foxtail millet.