Ravender Singh

Soil physical quality as influenced by long-term application of fertilizers and manure under maize-wheat system.

Soil physical environment as affected by long-term fertilizer experiment application in a maize-wheat system on sandy loam soils of India was characterized and quantified using a unified soil physical quality index (S). Treatments were 100% and 150% of recommended nitrogen, phosphorus, and potassium (NPK); 100% NPK + farmyard manure; 100% NPK + sulfur; and control (no fertilizer or manure). Soil aggregation, bulk density, organic carbon in bulk soil (SOC) and aggregates, pore-size distribution, saturated hydraulic conductivity, field capacity moisture content, and plant-available water content were evaluated. Most of the effects were pronounced in 0- to 15-cm layer. Better aggregation was found with 100% NPK + farmyard manure, where macroaggregates were greater than 50% of total soil mass. Aggregation indices were positively and significantly correlated with SOC in 8- to 4-mm aggregates. Bulk density was significantly lower (1.51 Mg m−3) with manure, corresponding to maximum SOC content (6.8 g kg−1). The field capacity moisture content, plant-available water content, and saturated hydraulic conductivity were significantly higher in manure plots. Transmission and storage pores were more abundant in manure-treated plots. Effects of 150% NPK or 100% NPK + sulfur doses was better compared with 100% NPK, indicating that the recommended dose of NPK was suboptimal to maintain the desired soil physical health. Close associations of S with soil physical parameters was obtained, indicating potential of S in quantifying the modifications of soil physical environment through fertilizer and manure applications.

Changes in seed water status as characterized by NMR in developing soybean seed grown under moisture stress conditions

Changes in water status of developing seeds of Soybean (Glycine max L. Merrill.) grown under different moisture stress conditions were characterized by proton nuclear magnetic resonance (NMR)- spin-spin relaxation time (T2). A comparison of the seed development characteristics, composition and physical properties indicated that, characteristics like seed weight, seed number/ear, rate of seed filling increased with development stages but decreased with moisture stress conditions. The NMR- spin-spin relaxation (T2) component like bound water increased with seed maturation (40-50%) but decreased with moisture stress conditions (30-40%). The changes in seed water status to increasing levels of moisture stress and seed maturity indicates that moisture stress resulted in more proportion of water to bound state and intermediate state and less proportion of water in free-state. These changes are further corroborated by significant changes in protein and starch contents in seeds under high moisture stress treatments. Thus seed water status during its development is not only affected by development processes but also by moisture stress conditions. This study strongly indicated a clear moisture stress and development stage dependence of seed tissue water status in developing soybean seeds.

Predicting Wheat Grain and Biomass Yield Using Canopy Reflectance of Booting Stage

Field experiment was conducted in a sandy loam soil of Indian Agricultural Research Institute, New Delhi during the year 2011–13 to see the effect of irrigation, mulch and nitrogen on canopy spectral reflectance indices and their use in predicting the grain and biomass yield of wheat. The canopy reflectances were measured using a hand held ASD FieldSpec Spectroradiometer at booting stage of wheat. Four spectral reflectance indices (SRIs) viz. RNDVI (Red Normalized Difference Vegetation Index), GNDVI (Green Normalized Difference Vegetation Index), SR (Simple Ratio) and WI (Water Index) were computed using the spectral reflectance data. Out of these four indices, RNDVI, GNDVI and SR were significantly and positively related with the grain and biomass yield of wheat whereas WI was significantly and negatively related with the grain and biomass yield of wheat. Calibration with the second year data showed that among the SRIs, WI could account for respectively, 85xa0% and 86xa0% variation in grain and biomass yield of wheat with least RMSE (395xa0kgxa0ha−1 (15xa0%) for grain yield and 1609xa0kgxa0ha−1 (20xa0%) for biomass yield) and highest d index (0.95 for grain yield and 0.91 for biomass yield). Therefore it can be concluded that WI measured at booting stage can be successfully used for prediction of grain and biomass yield of wheat.

Cropping practices, soil properties, pedotransfer functions and organic carbon storage at Kuanria canal command area in India

Effects of cropping practices on soil properties viz. particle size distribution, pH, bulk density (BD), field capacity (FC, -33 kPa), permanent wilting point (PWP, -1500 kPa), available water capacity (AWC) and soil organic carbon (SOC) were assessed. The pedotransfer functions (PTFs) were developed for saturated hydraulic conductivity (Ks), water retention at FC and PWP of soils for different sites under major cropping system in a canal irrigated area. The results revealed that the soils are mainly composed of sand and clay with the clay contents ranging from 29.6 to 48.8%, BD of 1.44-1.72xa0Mgxa0m-3, and 0.34 to 0.95% SOC. The Ks decreased, and water retention at FC, PWP and AWC increased significantly with soil depth due to greater clay contents in lower soil depths. The PTFs were best represented as the power functions for prediction of Ks with clay content as predictor variable; whereas the PTFs for water retention at FC and PWP were better represented as the exponential functions. SOC content was higher under rice-sugarcane crop rotation compared to other systems. SOC storage in the surface layer was higher in rice-sugarcane rotation (18.90-20.53xa0Mgxa0ha-1) than other sites. The developed PTFs would be very useful in soil and water management strategies for the study area or elsewhere having similar soil and cropping practices. The information on SOC storage in the Kuanria region would help for better soil and crop planning in future.

Effect of Organic Inputs on Strength and Stability of Soil Aggregates Under Rice-Wheat Rotation

Abstract The study aims to elucidate the impact of organic inputs on strength and structural stability of aggregates in a sandy loam soil. Tensile strength, friability and water stability of aggregates, and the carbon contents in bulk soil and in large macro (>2 mm), small macro (0.25-2 mm), micro (0.053-0.25 mm) and silt+clay size (<0.053) aggregates were evaluated in soils from a long-term experiment with rice-wheat rotation at Modipuram, India, with different sources and amounts of organic C inputs as partial substitution of N fertilizer. Addition of organic substrates significantly improved soil organic C contents, but the type and source of inputs had different impacts. Tensile strength of aggregates decreased and friability increased through organic inputs, with a maximum effect under green gram residue (rice)-farmyard manure (wheat) substitution. Higher macroaggregates in the crop residue- and farmyard manure-treated soils resulted in a higher aggregate mean weight diameter, which also had higher soil organic C contents. The bulk soil organic C had a strong relation with the mean weight diameter of aggregates, but the soil organic C content in all aggregate fractions was not necessarily effective for aggregate stability. The soil organic C content in large macroaggregates (2-8 mm) had a significant positive effect on aggregate stability, although a reverse effect was observed for aggregates <0.25 mm. Partial substitution of nitrogen by organic substrates improved aggregate properties and the soil organic C content in bulk soil and aggregate fractions, although the relative effect varied with the source and amount of the organic inputs.

Estimating S-index, unsaturated hydraulic conductivity and diffusivity through RETC in Indian Agricultural Research Institute farm

The hydraulic properties of vadoze zone like hydraulic conductivity, diffusivity and soil water retention characteristics are required to study soil water, nutrient and pollutant dynamics and their management. Surface layer of ten master profiles of Indian Agricultural Research Institute (IARI) farm, New Delhi were studied for different physicochemical and hydraulic properties. All ten master profiles were grouped under the order Inceptisol, subgroup Typic Haplustept and hyperthermic soil temperature regime. The soil water retention data were measured for all the sample layers and fitted to van Genuchten model using RETC software. The R2 value of fitted curve varied between 0.98 to 0.99 with residual sum of squares from 0.001 to 0.003. The θr value varied between 0.0332 to 0.0760 cm3 cm−3 and the saturated water content between 0.4665 to 0.3613 cm3 cm−3. In the present study, α ranged between 0.0018 to 0.0164 cm−1. The n value varied between 1.381 to 2.437. Combined for all profiles the prediction equation developed for K(θ) is K(θ) = 1.17×106×θ11.93 and D(θ) is D(θ) = 2.07×107× θ7.71 with R2 value of 0.77 both for K(θ) and D(θ). The Sindex varied between 0.068 to 0.128. The S-index was significantly positively correlated with θr (r = 0.73*), θs (r = 0.64*), n (r = 0.97**) and significantly negatively correlated with α (r = -0.80**). The S-index value for all the 10 master profiles were more than 0.050 indicating very good physical quality for all the 10 master profiles of IARI experimental farm.