Usha Kiran Chopra

Bio: Usha Kiran Chopra is an academic researcher from Indian Agricultural Research Institute. The author has contributed to research in topics: Irrigation & Loam. The author has an hindex of 9, co-authored 18 publications receiving 642 citations.

Spatial variability of soil properties and its application in predicting surface map of hydraulic parameters in an agricultural farm

Abstract: Knowledge of spatial variation of soil properties is important in precision farming and environmental modelling. Spatial distribution of water content at field capacity (FC) and permanent wilting point (PWP) at different zones of a farm governs the available water for plant growth. These two soil hydraulic parameters play key roles in crop selection for different blocks of a farm, and in scheduling irrigation of crops in a field. In this study, spatial variation of bulk density organic carbon, silt and clay contents for two soil depths (0-15 and 15-30 cm) in the agricultural farm of the Indian Agricultural Research Institute, New Delhi were quantified and the respective surface maps were prepared through ordinary kriging. Particle size distribution shows better spatial correlation structure than bulk density and organic carbon content. Gaussian model fits well with experimental semivariogram of bulk density, and silt and clay contents. Hole-effect model was found to be the best to fit the experimental semivariogram of organic carbon content. Spatial correlation structure for both surface (0-15 cm) and subsurface (15-30 cm) soil layer remains the same, but the magnitude of spatial correlation differs. Cross-validation of the kriged map shows that spatial prediction of basic soil properties using semivariogram parameters is better than assuming mean of observed value for any unsampled location. Pedo-transfer functions were coupled with the surface map of basic soil properties to generate a map of water content at FC and PWP. Evaluation of spatial maps of θ FC and θ PWP showed reasonable accuracy of these two hydraulic parameters for farm-level or regional-scale application.

Assessment of plant nitrogen stress in wheat Triticum aestivum L. through hyperspectral indices

Abstract: A field experiment with wheat was conducted with four different nitrogen and four different water stress levels, and hyperspectral reflectances in the 350–2500 nm range were recorded at six crop phenostages for two years 2009–2010 and 2010–2011. Thirty-two hyperspectral indices were determined using the first-year reflectance data. Plant nitrogen N status, characterized by leaf nitrogen content LNC and plant nitrogen accumulation PNA, showed the highest R 2 with the spectral indices at the booting stage. The best five predictive equations for LNC were based on the green normalized difference vegetation index GNDVI, normalized difference chlorophyll index NDCI, normalized difference705 ND705 index, ratio index-1dB RI-1dB and Vogelman index a VOGa. Their validation using the second-year data showed high R 2 >0.80 and ratio of performance to deviation RPD; >2.25 and low root mean square error RMSE; R 2 > 0.80. The corresponding RMSE and RE of these ranged from 1.39 to 1.13 and from 24.5% to 33.3%, respectively. Although the predicted values show good agreement with the observed values, the prediction of LNC is more accurate than PNA, as indicated by higher RMSE and very high RE for the latter. Hence, the plant nitrogen stress of wheat can be accurately assessed through the prediction of LNC based on the five identified reflectance indices at the booting stage.

Cropping system effects on soil quality for three agro-ecosystems in india

Abstract: Soil quality integrates the effects of soil physical, chemical and biological attributes. Some of them are dynamic in nature and behave differentially in various agro-ecosystems (AESs) and are quantified in terms of a soil quality index (SQI). An attempt has been made in this paper to develop an SQI based on a minimum data set (MDS), which could be used to evaluate the sustainability of the crop production in three varying AESs in India, namely sub-humid, semi-arid and arid. Thirteen indicators were utilized to develop the SQI from the properties measured from the surface soil layer (0–15 cm). Each indicator of the MDS was transformed into a dimensionless score based on scoring functions (linear and non-linear) and integrated into four SQIs. The weighted non-linear index (WNLI) was identified as the most sensitive for all the AESs and was recommended as an index for future assessments. Based on this index, the quantification of soil quality under several cropping systems was carried out for sub-humid, semi-arid and arid AESs and the most suitable cropping system was identified. WLNI was positively and significantly correlated (R2 = 0.79, p < 0.01) with wheat equivalent yield for all the cropping systems. This clearly indicated that the index may be used satisfactorily for quantifying soil quality.

Ridge-Furrow Mulching Systems—An Innovative Technique for Boosting Crop Productivity in Semiarid Rain-Fed Environments

Abstract: Increasing food demands by a growing human population require substantial increases in crop productivity. In rain-fed arid and semiarid areas where the water supply is limited, an increase in the precipitation use efficiency (PUE) is the key to reach this goal. This chapter examines the scientific basis of a ridge-furrow mulching system (RF system) for increasing PUE, and summarizes the effects of this system on crop performance, microclimates, soil attributes, and environmental sustainability. Studies have shown that using crop straw, plastic film, or gravel–sand materials to mulch the soil surface significantly reduces the evaporation of soil moisture, increases water availability to crop plants, and decreases soil erosion caused by wind and water. Plastic mulching increases topsoil temperature during cool spring, promoting plant growth; during hot summer, straw mulching can moderate soil temperature, preventing the topsoil from reaching temperatures that inhibit plant growth. Ridge furrows with plastic mulching on the ridges and crop straw covering the furrows channel water to the furrows, and enhance soil water infiltration and water availability to the crop. Microclimates under mulched ridges and furrows favor soil microbial activity, increase soil biodiversity, and improve environmental benefits. The effectiveness of ridge-furrow systems is reflected in increased crop yields (20–180%) compared with that of the conventional-flat planting. Although more research is required to document physiochemical strengths, technique details and potential drawbacks, and more importantly to define long-term sustainability, we strongly suggest that RF systems are an innovative approach for increasing crop water availability, improving soil productivity, and enhancing food security for arid and semiarid rain-fed areas.

Recent advances in mulching materials and methods for modifying soil environment

Abstract: The global temperature has been increasing over the years due to climate change that, directly or indirectly, affects water and energy consumptions in the agriculture sector. The application of mulching practices reduces soil evaporation, conserves soil moisture, suppresses weed growth, controls soil structure and temperature, influences soil micro-organisms, and is aesthetically pleasing. This study has reviewed 189 published research papers, which described the effects of various mulching materials and methods on soil and environment that influence crop productivity. This paper describes the extent of influence of different mulching materials and methods on the hydrothermal environment of soils. It is imperative to know the processes that control soil environments under various mulching conditions and the effects of mulching materials on crop yield, productivity and water use efficiency. These issues of mulching are the prime concerns of this review study. Plastic mulching materials have a greater importance than the organic ones to control soil environment and increase crop yield. But, the organic mulching materials are inexpensive and environment friendly. The selection of an appropriate mulching material is, however, guided by crop type, crop management practices and climatic conditions. Future research is needed on the effects of low-cost biodegradable mulching materials on microclimate modifications, soil biota, soil fertility, crop growth and crop yields.