Varinderpal Singh

Punjab Agricultural University | PAU · Department of Soil Science

Crop residues are a neglected source of sustainable agriculture since they are produced in large quantities, yet farmers frequently burn them. The purpose of this study was to assess the effects of nitrogen (N) application rate and residue management strategies for wheat production on changes in soil enzyme activity, microbial count, and chemical p...

Fertilizer nitrogen (N) management in long-grained aromatic basmati rice (Oryza sativa) is critical because both below and above the optimum N application rate adversely affects yield. Multi-location field studies were conducted in northwestern India to formulate a site-specific N management (SSNM) strategy for basmati rice by monitoring the greenn...

The present study was conducted to establish prediction models for grain yield and nitrogen (N) uptake using normalized difference vegetation index (NDVI) measurements with the GreenSeeker optical sensor for different cultivar groups of basmati rice (Oryza sativa L.) and to define the optimum sensing timing. Sensor readings were collected at 21, 28...

A number of optical sensing tools are now available which can potentially be used for refining need-based fertilizer N topdressing decisions. Algorithms for estimating field-specific fertilizer N needs are based on prediction of yield when crop is growing in the field. The present study was conducted to establish and validate yield prediction model...

Site-specific fertilizer nitrogen (N) management using chlorophyll meter (SPAD meter) can help drawing in-season need-based N topdressing decisions. However, SPAD meter based threshold chlorophyll value to trigger supplement N in spring maize is indistinct. Field studies were conducted for two years in sub-tropical and sub-humid climate to study va...

Canopy reflectance measurements using active optical sensors have emerged as potential solution to draw in-season nitrogen (N) topdressings in cereals. Site-specific need-based N management strategy using a GreenSeeker optical sensor was developed and evaluated in spring maize. Four field experiments were conducted at two locations during 2017 and...

Over-application of fertilizer nitrogen (N) in spring maize results in low fertilizer N use efficiency. Site specific need-based fertilizer N management in spring maize using chlorophyll meter (SPAD meter) and GreenSeeker optical sensor was compared with soil-test recommended N applications in field experiments conducted for two years during 201...

Use of Fertilizer Nitrogen (N) to increase food production constituted one of the major factors in supporting population growth in the twentieth century. The trend continues in the twenty-first century, particularly in the developing countries of the world. Because a part of the N applied as fertilizer is prone to be lost from the soil–plant system...

Fertilizer nitrogen (N) is one of the most important nutrient inputs in global crop production. The general fertilizer N management practices in field crops consist of applying preset N doses at specified growth stages in multiple splits. Blanket or soil-test-based recommendations ignore temporal and spatial variability in soil N supply and crop de...

A 4 years field study was conducted to improve nitrogen (N) and phosphorus (P) use efficiencies in wheat (Triticum aestivum L.) using arbuscular mycorrhizal fungi (AMF) and precision N management. Split plot design was employed to rationalize N and P fertilizer use in two different experiments with AMF in the main plot and fertilizer application pr...

Nitrogen is one of the most important macronutrients for crop growth and metabolism. To identify marker-trait associations for complex nitrogen use efficiency (NUE)-related agronomic traits, field experiments were conducted on nested synthetic wheat introgression libraries at three nitrogen input levels across two seasons. The introgression librari...

In-situ field studies were conducted for three consecutive baby corn (Zea mays L.) growing seasons to quantify the amount of reactive N flowing beyond the rhizosphere while defining mitigation strategies. The N applications based on plant need were agronomically more efficient than the fixed-time blanket N applications. Average area-scaled leachate...

Fertilizer nitrogen (N) is the major input for food production. Excessive and untimely fertilizer N topdressings to achieve high yields are common among the farmers in the major food producing regions of Asia. A four year field study was conducted to validate precision N management strategies in wheat (Triticum aestivum L.; variety PbW 550) through...

Nitrogen is one of the most important macronutrients for crop growth and metabolism. To identify marker-trait associations for complex NUE-related agronomic traits, field experiments were conducted on nested synthetic wheat introgression libraries at three nitrogen input levels across two seasons. The introgression libraries were genotyped using th...

Predicting in-season crop yield is a unique tool for drawing important crop management decisions for precision farming. Field experiments were conducted at two locations in northwestern India under different agro-climatic zones to predict and validate spring maize yield using various in-season spectral indices. The spectral properties measured with...

Background: Excessive application of nitrogen (N) fertilizer in cereal crops not only decreases the N use efficiency but also accelerates greenhouse gas (GHG) emission. Aim: To improve N use efficiency in wheat (Triticum aestivum L.) using precision N management and coating seeds with arbuscular mycorrhizal fungi (AMF). Methods: Field experiment la...

Fertilizer nitrogen (N) is one of the most important nutrient inputs in global crop production. The general fertilizer N management practices in field crops consist of applying preset N doses at specified growth stages in multiple splits. Blanket or soil-test-based recommendations ignore temporal and spatial variability in soil N supply and crop de...

Consumption of fertilizer nitrogen (N) in India is increasing at a rate faster than that in the world because crop production per unit of applied N is not increasing as much as observed in many countries in Western Europe and North America. Due to gradual reduction in crop yield response and low fertilizer N use efficiency, there is an urgent need...

Application of fertilizer nitrogen (N) and phosphorus (P) in excess of crop requirement causes nutritional imbalances in soil along with economic and ecological losses. The optical sensors (leaf color chart, chlorophyll meter, and GreenSeeker) help guide real-time N topdressing decisions and arbuscular mycorrhizal fungi (AMF) further improve nutrie...

Precision nitrogen (N) management sustains high grain yield with low N optimum dose and thus may help reduce the escape of reactive nitrogen from soils to the atmosphere. Two-year field studies were conducted at two locations in sub-tropical and sub-humid climate in Indo-Gangetic plains of South Asia with the objectives to establish precision N man...

In cereal crop production in South Asia, nitrogen fertilizers are generally managed as blanket recommendations formulated on the basis of crop response data averaged over large geographic areas. Blanket recommendations do not take into account the spatio-temporal variability in nitrogen supplying capacity of soils. In developed countries, improved...

Three-year multi-location field experiments were conducted in soils of varying inherent nitrogen (N) supply in diverse agro-climatic zones for improving productivity and mitigating N2O emissions in timely sown and late sown wheat. The biomass, total N uptake (TNU) and spectral properties were monitored at different growth stages. Biomass production...

A 5-year field study was conducted to improve nitrogen (N) and phosphorus (P) use efficiencies in wheat with the synergistic use of plant growth-promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF), and spectral properties for deriving need-based fertilizer N management decisions. Bio-fertilizer consortium inoculation on wheat seed im...

Increasing nitrogen fertilizer applications have sustained a growing world population in the 20th century. However, to avoid any further associated environmental damage, new sustainable agronomic practices together with new cultivars must be developed. To date the concept of nitrogen use efficiency (NUE) has been useful in quantifying the processes...

Dry direct-seeded aerobic rice (DSR) is an emerging attractive alternative to traditional puddled transplanted rice (PTR) production system for reducing labour and irrigation water requirements in the Indo-Gangetic plains (IGP) of India. The fertilizer N requirement of DSR grown with alternate wetting and drying water management may differ from tha...

In irrigated wheat as grown in northwestern India, fertilizer nitrogen (N) management following blanket recommendations is increasing resulting in stagnant yield levels with low N use efficiency. Site-specific nutrient management strategy to apply N as per need of wheat crop was formulated based on leaf colour measured by chlorophyll meter (Minolta...

Site-specific fertilizer nitrogen management (SSNM) could be the best management option to avoid excessive and untimely nitrogen (N) applications in wheat. Field experiments were conducted in soils of varying inherent fertility in diverse agro-climatic zones to provide SSNM strategy for wide range of wheat genotypes. The intensity of leaf colour gr...

SUMMARY Bagasse and rice husk are two important agro-industrial by-products that are used as fuel in the sugar and rice mill industries, thus producing large quantities of bagasse ash (BA; 0·05 of bagasse) and rice husk ash (0·20 of rice husk) as waste material. Applying BA and rice husk ash (RHA) to agricultural land improves yield, nutrient uptak...

An optical sensor-based fertilizer nitrogen (N) management strategy that relies on visible and near-infrared spectral response from plant canopies was evaluated for irrigated wheat in the northwestern India. GreenSeeker™ optical sensor-guided fertilizer N dose, computed from an estimate of potential yield and response index, takes into account both...

Precision nutrient management is one of the key components of the precision agriculture and governs all the major issues of improving productivity, sustainability, profitability and climate change related turbulences. Soil test based nutrient management recommendations have served the purpose of improving food grain production but have not improved...

Aphids have acquired the status of major pest in North-western plains of India. A complex of five species infests the wheat in this part of the country. The diatomaceous earth (DE) has the potential to substitute the most widely used method of chemical control. Laboratory and field investigations were conducted to evaluate the effectiveness of DE e...

Application of fertilizer N doses to rice (Oryza sativa L.) whenever leaf greenness as measured by chlorophyll meter (SPAD) and LCC falls below a fixed threshold is being extensively used for site-specific management of fertilizer N. As fixed threshold greenness varies with regions, rice cultivars and seasons, a dynamic threshold greenness concept...

Use of high rates of commercial nitrogen (N) fertilizers over the years has resulted in adverse effects on soil and environment health. Integrated use of fertilizer N and organic N sources is expected to reduce the N losses and improve N use efficiency. The present field experiment was conducted for two years to evaluate the effects of commercially...

Blanket fertilizer nitrogen (N) recommendations for large irrigated transplanted rice tracts lead to low N use-efficiency (NUE) due to field-to-field variability in soil N supply and seasonal variability in yield. To achieve high NUE, a fertilizer N management strategy based on visible and near-infrared spectral response from plant canopies using a...

Bagasse ash (BA) and rice husk ash (RHA) contain significant quantities of P and many other nutrients. Application of biomass ashes has been shown to improve crop yields and soil properties. The present experiment was conducted to determine the effect of BA and RHA application in combination with different doses of P fertilizer on soil enzyme activ...

Large field to field variability in inherent nitrogen (N) supply restricts efficient fertilizer N use when broad based blanket recommendations are used in cereals. Field experiments were conducted for 11 years (2000-2011) to evaluate threshold leaf colour greenness to guide in-season need based fertilizer N top-dressings in different rice, wheat...

Rice husk ash (RHA) and bagasse ash (BA) are available in large quantities in South Asian countries growing rice and sugarcane. Land application of RHA and BA is likely to influence chemistry of soil phosphorus (P) and thereby P adsorption and desorption. Laboratory studies were carried out to investigate the short-term and long-term effects of RHA...

Prediction of potential yields during crop growth season is important for successful agricultural decision-making. The objective of this study was to predict grain yield of dry direct-seeded rice (DDSR) using leaf greenness as measured by chlorophyll meter (SPAD) and leaf color chart (LCC) and using normalized difference vegetation index (NDVI) wor...

In the Indo-Gangetic plain in South Asia, fertilizer nitrogen (N) application to irrigated wheat in two split doses at planting and at crown root initiation (CRI) stages of the crop is the general recommendation. Farmers have a tendency to apply another dose of N at maximum tillering (MT) stage to avoid the risk of N deficiency. However, appropriat...

Fertile soils are a fundamental asset for a sustainable rice-wheat cropping systems followed in 13 Mha in the Indo-Gangetic plains (IGP). Managing practices for the rice-wheat cropping system are changing and in turn influencing soil fertility parameters. In long-term rice-wheat cropping, soil organic carbon content declined only in soils having hi...

Large quantities of rice husk ash (RHA), bagasse ash (BA) and coal fly ash (FA) are available in many Asian countries as waste materials, which create a serious disposal problem. Recycling of these ashes on agricultural land can help to improve physical and chemical fertility of soil. The present field experiment was conducted for three and half ye...

Robust relationships were observed between in-season GreenSeekerTM optical sensor based estimates of yield at Feekes 5-6 and 7-8 growth stages and actual wheat yields. Sensor-guided fertiliser N applications resulted in high yield levels and high N use efficiency. Application of 90 kg N/ha at planting, or in two equal doses at planting and crown ro...

Field experiments were conducted during 2006-08 to study the response of hybrid rice cultivar PHB 71 to fertilizer N and to study the possibility of improving N-use efficiency by affecting fertilizer N as per need of the crop as guided by leaf colour chart (LCC). Treatments included six rates of N application (0,60,90,120,150 and 180 kg/ha) applied...

Blanket fertilizer nitrogen (N) recommendations for large irrigated wheat tracts lead to low N-use efficiency due to field-to-field variability in soil N supply and seasonal variability in yield. To achieve high N use efficiency, a site-specific N management strategy using GreenSeeker™ optical sensor was evaluated. We conducted seven field experime...

Fertilizer nitrogen (N) is one of the major inputs in rice–wheat production systems in South Asia. As fertilizer N has generally been managed following blanket recommendations consisting of two or three split applications of preset rates of the total amount of N, improvement in N use efficiency could not be achieved beyond a limit. Feeding crop N n...

Modifications in fertilizer source and/or management can lead to reduced losses of N, high wheat yields and increased fertilizer N-use efficiency. Relative performance of neem (Azadirachta indica A Juss)-coated urea vis-à-vis ordinary urea applied to wheat (Triticum aestivum C. emend Fiori & Paol.) was studied when applied at different levels (48,...

Neem coated urea (NCU) applied to rice can result in high N use efficiency as it contains nitrification inhibition properties. Field experiments were conducted for three years (2005–2007) at Ludhiana (sandy loam soil) and Gurdaspur (clay loam soil) for evaluating the relative performance of NCU vis-à-vis ordinary urea as a source of N for transplan...

Poultry litter (PL) is an important nutrient source; however, no information is available regarding its value in supplying N and P in rice–wheat (RW) production. A three-year field study was conducted at Ludhiana, Punjab, India on a loamy sand soil to identify optimum combination of PL and N and P fertilizers for a sustainable RW production. The li...

Leaf colour chart (LCC) guides fertilizer nitrogen (N) application to rice as per requirement of the crop on the basis of a critical leaf colour. We evaluated need-based N management in on-farm experiments at 350 locations in the Indian Punjab during 2002 - 2005. Following LCC-based N management, from 9.4 - 54.2 kg N ha-1, with an average of about...

The contribution of different sized soil separates to various inorganic P fractions was investigated after 32 years of long-term fertilization under maize-wheat-cowpea fodder crop rotation. Phosphorus was applied as single super phosphate. A major portion (71.5%) of Olsen-P was extracted from sand size particles, and only 11.4% and 17.1% was presen...

Leaf colour chart (LCC) guides fertilizer nitrogen (N) application to rice as per requirement of the crop on the basis of a critical leaf colour. We evaluated need-based N management in on-farm experiments at 350 locations in the Indian Punjab during 2002 – 2005. Following LCC-based N management, from 9.4 – 54.2 kg N ha71, with an average of about...

Phosphorus availability from residual P sources in soil is virtually the chemistry of metastable P compounds, i.e., their solubility and interaction with other soil and plant components. Identification of these compounds in soils under long-term application of fertilizers and farmyard manure is unstated and is prerequisite to comprehend the process...

Transformations of applied phosphorus (P) to unavailable residual soil P is the major cause of limited P supply in most of the P-deficient soils. The effect of the incorporation of crop residues (rice straw [RS] and wheat straw [WS]) and organic manures (farmyard manure [FYM] and green manure [GM]) on P release in soil and its bio-availability to v...

An understanding of the adsorption–desorption behaviour of phosphate (P) in soils after three decades of long-term fertilization would be an invaluable supplement to our knowledge of the chemistry of P in soils and would assist in developing P application strategies for successive crops. With this objective and within the framework of a long-term e...

Laboratory studies were conducted in 100 cm long columns (10 cm ID) to study distribution and leaching of applied urea-N in a sandy loam and clay loam soils under upland and wetland moisture regimes. At 2 days after application, movement of N coincided with the wetting front in both the soils and under both the moistures regimes. Urea moved to deep...