Soil Carbon Dioxide Emissions from Sorghum–Sunflower Rotation in Rainfed Semi-arid Tropical Alfisols: Effects of Fertilization Rate and Legume Biomass Incorporation

The long-term effects of plant legume [horse gram (Macrotyloma uniflorum)] biomass incorporations were assessed in terms of carbon dioxide (CO2) emissions, soil quality parameters, and climatically influenced soil parameters in a dryland Alfisol under varying soil fertility conditions. Six selected treatments consisted of off-season legume incorporation (I) and no incorporation / fallow (F), each under three varying nitrogen and phosphorus fertilizer levels (viz., N0P0, N25P30, and N50P30). Soil moisture, soil temperature, soil surface carbon dioxide emission, soil dehydrogenases, and microbial biomass carbon (MBC) were monitored at three different crop situations [viz., Kharif period (KP), legume/fallow period (LP), and no crop period (NP)] at 14 different periods of the year. Incorporation practices resulted in greater rates of CO2 emission over fallow conditions during the Kharif and legume periods, whereas the emission rate was greater in fallow soils during the end of the legume and no crop periods. The increased rates of fertilizer doses also significantly increased the soil CO2 flux during the majority of the measurements. Beneficial effects of incorporation practices were observed in terms of high soil moisture (5–11%), low soil temperature (3–7%), and high content of MBC over without incorporations. Correlation studies indicated that the soil property MBC was found to be the greatest significant variable with CO2 emission in all the fertilizer treatments under biomass-incorporated soils. These results indicated the undesirable (in terms of CO2 fluxes) and desirable (soil biological and other parameters) effects of legume biomass incorporation and fertilizer application and their significance in improving soil quality and greenhouse gas (GHG) emissions in dryland Alfisols of semi-arid tropics

Evaluation of crop production systems based on locally available biological inputs

Crop production systems that require chemical fertilizers, pesticides, machinery for tillage, and irrigation water are expensive. In countries such as India, they have started to undermine the water security of future generations, contributing to soil and water pollution particularly when synthetic pesticides are not used properly. It is true that agriculture as practiced 100 years ago without modern inputs had lower productivity than present systems of production. However, many premodern practices, such as the use of organic manures to enhance soil fertility and of herbal extracts to protect crops, can be made more efficient by the scientific knowledge that has been gained over the past century, making crop production more sustainable while still achieving high productivity

Biology and genetic improvement of Jatropha curcas L.: a review

Bio-diesel is a fast-developing alternative fuel in many developed and developing countries of the world. The bio-diesel production from vegetable oils during 2004–2005 was estimated 2.36 million tonnes globally. Of this, EU countries accounted for about 82% and USA about 6%. Global bio-diesel production is set to reach some 24 billion litres by 2017. Shortage of edible oil for human consumption in developing countries does not favour its use for bio-diesel production. Hence non-edible oil from crops like Jatropha (Jatropha curcas) and Pongamia (Pongamia pinnata) is favoured for bio-diesel production and the trend is expected to continue. Especially J. curcas has gained attention in tropical and sub-tropical countries and has spread beyond its centre of origin, because of its hardiness, easy propagation, drought endurance, high oil content, rapid growth, adaptation to wide agro-climatic conditions, and multiple uses of plant as a whole. The full potential of J. curcas has not been realized due to several technological and economic reasons. One of the major reasons is the lack of high yielding varieties with high oil content. In this review, we attempt to discuss the currently available information on Jatropha species identity, taxonomy and description, distribution and ecological requirements of the species, possibilities of exploitation of genetic potentiality, exploitation of existing diversity for yield and oil content by direct selection, hybridization and creation of diversity by mutation, and biotechnological interventions

Heavy-Metal Concentrations in Sediments Collected from ICRISAT Lake, Patancheru, India

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

Simple and accurate method for routine analysis of heavy metals in soil, plant, and fertilizer

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 digestion, an analyst can perform more than 100 analyses in a working da

Variable indicators for optimum wavelength selection in diffuse reflectance spectroscopy of soils

Diffuse reflectance spectroscopy (DRS) operating in 350–2500 nm wavelength range is fast emerging as a rapid and non-invasive technique for analyzing multiple soil attributes. Because the spectral reflectance values in this range of wavelengths are highly co-linear, it is important to select relevant spectral information from the reflectance spectra to build a robust spectral algorithm. The objective of this study is to examine the utility of different variable indicators such as partial least squares regression (PLSR) coefficients (β), variable influence on projection, squared residual (SqRes), correlation coefficient (r), biweightmidcorrelation (bicor), mutual information based adjacency value (AMI), signal-to-noise ratio (StN), covariance procedures (CovProc) and their combinations in conjunction with an ordered predictor selection (OPS) approach for selecting optimum number of spectral variables (NSV) which could improve DRS model performance. The approach was tested with the PLSR models of pH, organic carbon, extractable iron (Fe), sand and clay contents and geometric mean diameter in Vertisols and Alfisols. The prediction accuracy of best models selected via OPS approach was found to be superior to full-spectrum (NSV = 2048) model for all the soil attributes. The percent decrease in RMSE value was found to be highest for Fe (14%, NSV = 79) in Alfisols followed by pH (9%, NSV = 660) in Vertisols while it varied between 3 and 8% for other soil attributes. Although the results were not conclusive in favor of one specific variable indicator, the CovProc and bicor were found to be more appropriate for accurate and moderate DRS models in this study, respectively. The overall results of this study advocate the use of OPS approach with variable indicators and their combinations as a promising strategy to develop simple and effective DRS models for soils

Improved crop productivity and rural livelihoods through balanced nutrition in the rainfed semi-arid tropics

Diagnostic soil analysis in targeted clusters of eight districts in Andhra Pradesh revealed critical deficiencies of sulphur (61 to 98%), boron (23 to 98%) and zinc (45 to 85%) in addition to that of soil carbon (25 to 97%), and phosphorus (14 to 84%) which are apparently holding back the productivity potential. The soil test based application of sulphur, boron and zinc together increased productivity by 8 to 102% in cotton, groundnut, castor, sorghum, greengram, cowpea, chickpea and maize. Economic assessment reveal that per rupee invested as additional cost (` 1,400/- to ` 2,150/-) gave ` 1.6 to 28.5 in return. Residual benefits of balanced nutrition were observed during 4 succeeding seasons. Soil health improved in balanced nutrition plots, inspite of higher yields and nutrient removal. The results showed that balanced nutrition is the way forward to increase crop productivity through resilience building of production systems and improve farm based livelihoods in the SAT regions

Dependency measures for assessing the covariation of spectrally active and inactive soil properties in diffuse reflectance spectroscopy

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

Evaluation of stratification criteria for regional assessment of soil chemical fertility parameters in semi-arid tropical India

Statistically sound soil sampling strategy is a prerequisite for assessing the soil fertility status of a region. We tested a stratified, random sampling methodology to ascertain whether surface geology, microwatershed, position on the toposequence, and size of farm holding explained the differences in the fertility parameters of soils in the semi-arid tropical region of Karnataka State, India. Descriptive statistics revealed that out of 119 farmer fields sampled, many were deficient in the following nutrients: 50% in available phosphorous (P), 78% in boron (B), 67% in zinc (Zn), and 72% in sulfur (S). Discriminant analysis indicated that fertility studies on a regional scale need to include good representation of soil heterogeneity based on parent material (surface geology), hydrological properties, and positions on toposequence but not the size of the farm holding. The proposed stratified random sampling technique enabled representation of the heterogeneity in the whole population even with a small sample set siz

Increased proportion of active soil N in Breton loam under cropping systems with forages and green manures

Total soil N and N mineralization rate partially ctririct&iie the influence olvariouJcropping systems on the growth of.sequent.crop.s in a rotation' The objectives of this study were to (1) quantify the relationship among cropping system, total N and mineralizable N, and (2) compare amount of N mineralized under'controlled laboratory conditions-with pianl N uptake under green]ouse conditi:ns. Three cropping systems that have been in operation between 9 and 60 yr on a Gray-Luvisol (Breton loam; were ^selected . They included: (1) an ag.lo: ecological (lnn) d-yr rotation involving fabibeans as gr-een manure (AER1 sampled after the_first lababean crop-?nq AER? ,u-pied after 3 yr of continuous forage)l (2) continuous grain system (CG), with fertilizer N at 90 kg ha-'^yr- '; inttrated in 1980 and considered established in f"98i; i3) a classicial Ereton iotation (CBR) involving 9]o-ng-term (ca. 1930) 5-yr rotation with forages and cereals and no return of.ciop residues (CBR1 fertilized with P-K-S and CBR2 unfertilized). We cautio_n that not all ohlses of each rotation were sampled: bur conclusions pertain to N-mineralization potential in soil samples immediately preceding barley as sequent crop in each rotation. The rate ofN mineralization declined with time, but it remained greater than iero aftei 20 wi AER2 > > CBRI > CBR2 : CG. Mineralizable soil N, following one cycle of the AER rotation, was almost double that following 60 yr of the CBR rotation. Data for mineral-N accumulation under laboratory conditions were described best by a single-component expo-n-ential model. Legume-based rotations were associated with increased total soil N and a greater proportional increase in active N than in total soilN. Active N was least in soil under the CG system. The incubation-extraction procedure resulted in higher estimates of mineralizable N than did the plant-uptake method; liowever, the ranking of N-supplying power of soils was the same