O. P. Choudhary

Organic amendments decomposability influences microbial activity in saline soils

ABSTRACT Organic amendments with contrasting biochemical properties were investigated by conducting an incubation experiment in soils irrigated with different levels of saline water. Soil samples were taken from a long-term experimental field plots irrigated with normal water and saline water having electrical conductivity (EC) 6 and 12 dS m−1, respectively. Finely ground biochar, rice straw (RS), farm yard manure (FYM) and glucose were added at two rates (1% and 2.5% carbon basis) and incubated for 8 weeks at 25°C. Cumulative respiration (CR), microbial biomass carbon and available nutrients (nitrogen and phosphorus) were negatively correlated with EC, irrespective of the source and amount of added carbon (C). Compared with non-saline soil, at EC 12, relative decrease in CR was lowest with glucose (21.0%) followed by RS (32.0%), FYM (46.0%) and biochar (55.0%). Dissolved organic carbon was positively correlated with salinity and its concentration was higher in treatments with higher rate of C addition (2.5% C). This study showed decomposability of organic amendments and their rate of addition determines microbial activity in saline soils. Further, lower nitrogen (N) release from amendments under saline conditions limits microbial ability to utilize available C for satisfying their energy needs.

Influence of Long‐Term Sodic‐Water Irrigation, Gypsum, and Organic Amendments on Soil Properties and Nitrogen Mineralization Kinetics under Rice–Wheat System

Abstract Influence of long‐term sodic‐water (SW) irrigation with or without gypsum and organic amendments [green manure (GM), farmyard manure (FYM), and rice straw (RS)] on soil properties and nitrogen (N) mineralization kinetics was studied after 12 years of rice–wheat cropping in a sandy loam soil in northwest India. Long‐term SW irrigation increased soil pH, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) and decreased organic carbon (OC) and total N content. On the other hand, application of gypsum and organic amendments resulted in significant improvement in all these soil properties. Mineralization of soil N ranged from 54 to 111 mg N kg−1 soil in different treatments. Irrigation with SW depressed N mineralization. In SW‐irrigated plots, two flushes of N mineralization were observed; the first during 0 to 7 d and the second after 28 d. Amending SW irrigated plots with GM and FYM enhanced mineralization of soil N. Gypsum application along with SW irrigation reduced cumulative N mineralization at 56 days in RS‐amended plots but increased it under GM‐treated, FYM‐treated, or unamended plots. Nitrogen mineralization potential (No) ranged from 62 to 543 mg N kg−1 soil. In the first‐order zero‐order model (FOZO), the easily decomposable fraction ranged from 5.4 to 42 mg N kg−1 soil. Compared to the first‐order single compartment model, the FOZO model could better explain the variations in N mineralization in different treatments. Variations in No were influenced more by changes in pH, SAR, and ESP induced by long‐term SW irrigations and amendments rather than by soil OC.

Forms and Uptake of Manganese in Relation to Soil Taxonomic Orders in Alluvial Soils of Punjab, India

ABSTRACT Different forms of manganese (Mn) were investigated, including total, diethylenetriamine penta-acetic acid (DTPA) extractable, soil solution plus exchangeable (Mn), Mn adsorbed onto inorganic sites, Mn bound by organic sites, and Mn adsorbed onto oxide surfaces, from four soil taxonomic orders in northwestern India. The total Mn content was 200–950 mg kg−1, DTPA-extractable Mn content was 0.60–5.80 mg kg−1, soil solution plus exchangeable Mn content was 0.02–0.80 mg kg−1, Mn adsorbed onto inorganic sites was 2.46–90 mg kg−1, and Mc adsorbed onto oxide surfaces was 6.0–225.0 mg kg−1. Irrespective of the different fractions of Mn their content was generally greater in the fine-textured Alfisols and Inceptisols than in coarse-textured Entisols and Aridisols. The proportion of the Mn fractions extracted from the soil was in the order as follows: Adsorbed onto oxide surfaces > adsorbed onto inorganic site > organically bound > DTPA > soil solution + exchangeable. Based on coefficient of correlation, the soil solution plus exchangeable Mn, held onto organic site and oxide surface (amorphous) and DTPA-extractable Mn, increased with increase in organic carbon of the soil. The two forms, adsorbed onto inorganic site (crystalline) and DTPA extractable, along with organic carbon, increased with increase in clay content of the soil. DTPA-Mn and Mn adsorbed onto oxide surfaces and held on organic site decreased with increased with an increase in calcium carbonate and pH. Total Mn was strongly correlated with organic carbon and clay content of soil. Among the forms, Mn held on the organic site, water soluble + exchangeable and adsorbed onto oxide surface were positively correlated with DTPA-extractable Mn. DTPA-extractable Mn seems to be a good index of Mn availability in soils and this form is helpful for correction of Mn deficiency in the soils of the region. The uptake of Mn was greater in fine-textured Inceptisols and Alfisols than in coarse-textured Entisols and Aridisols. Among the different forms only DTPA-extractable Mn was positively correlated with total uptake of Mn. Among soil properties Mn uptake was only significantly affected by pH of the soil.

Wheat Response to Increasing Levels of Residual Alkalinity in Irrigation Water in a Semi-Arid Region

Response of wheat (Triticum aestivum L. emend. Fiori & Paol.) cultivars to irrigation with sodic waters having high residual alkalinity is not well known. The objective of this field investigation (2006–07 to 2008–09) was to study the response of three wheat cultivars (PBW 343, PBW 502, and PBW 550) to four levels of residual sodium carbonate (RSC) in irrigation water: 0, 3, 6.5, and 10 mmolc L−1 at Ludhiana. Another field study (2004–05 to 2006–07) involving PBW 343 and PBW 502 was carried out using tubewell water irrigation (RSC of 5.5 mmolc L−1) at Bathinda. Increase in RSC significantly increased soil pH and exchangeable sodium percentage and decreased grain yield of all three cultivars at Ludhiana. The three cultivars responded differentially to RSC levels. Data pooled across three years at Ludhiana revealed that at 3 mmolc L−1 RSC, yields of PBW 343 and PBW 502 were similar, but cultivar PBW 343 produced higher yield than PBW 502 and PBW 550 when irrigated with water containing 6.5 and 10 mmolc L−1 RSC. Cultivar PBW 550 had the lowest grain yields at all levels of RSC. Grain yield at 10 mmolc L−1 RSC was 3.9, 3.3, and 2.9 Mg ha−1 for PBW 343, PBW 502, and PBW 550, respectively. No significant effect of RSC of irrigation water on any grain quality parameter of cultivars was observed. At Bathinda, cultivar PBW 343 produced 11% higher grain yield than PBW 502 under tubewell irrigation. At both the locations, cultivar PBW 343 performed better with respect to yield than the other cultivar/s and, therefore, should be preferred on soils irrigated with waters containing RSC higher than 5 mmolc L−1.

Site-specific Fertilizer Nitrogen Management in Irrigated Wheat using Chlorophyll Meter (SPAD meter) in the North-western India

In irrigated wheat as grown in north-western 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 SPAD meter) as a function of soil N supply. The SPAD meterguided protocols for fertilizer N application at crown root initiation (CRI) and maximum tillering (MT) stages, coinciding with first two irrigations, were evaluated through a series of field experiments with seven wheat varieties in Ludhiana and Gurdaspur in north-western India. Threshold leaf greenness levels equivalent to SPAD readings <40, <42.5 and <45 were tested in terms of (i) whether to apply fertilizer or not, and (ii) deciding as to how much fertilizer N needs to be applied as per requirement of the crop. At CRI stage, when the crop was about two-week old, fertilizer N dose could not be guided by SPAD meter because due to application of a basal dose of N at planting variation in the leaf colour was found to be very small. Also, due to small size of leaves at CRI stage it was difficult to use SPAD meter to measure leaf colour. Application of 30 kg N ha−1 at planting, 45 kg N ha−1 at CRI stage and a dose of 30 or 45 kg N ha−1 at MT stage depending upon leaf greenness to be ≥ or < SPAD 42.5, respectively produced wheat grain yields at par with blanket recommendation for fertilizer N, but with higher fertilizer N use efficiency.

Performance of Some Wheat Cultivars Under Saline Irrigation Water in Field Conditions

ABSTRACT Most of the crop salt tolerance studies are often conducted in a glasshouse and are limited under field conditions. Therefore, the present research study was conducted under field conditions to evaluate the performance of six wheat cultivars at five salinity levels (EC 0, 3, 6, 9, and 12 dS m−1) in split plot design with three replications. Increasing salinity significantly increased soil pH, electrical conductivity (EC), and sodium adsorption ratio (SAR). Yield parameters of different cultivars were affected more at higher salinity levels than lower in two years. Data over two years revealed that up to EC 9 dS m−1 cultivars PBW 658 and HD 2967 performed better on the absolute yield basis but PBW 621 produced higher relative yield. At EC 12 dS m−1, PBW 658 produced significantly higher grain yield (4.23 t ha−1) than cultivars HD 2967 (4.11 t ha−1) and PBW 621 (3.99 t ha−1); therefore, should be preferred at salinity more than 9 dS m−1.

Microbial Activity Is Constrained by the Quality of Carbon and Nitrogen under Long-term Saline Water Irrigation

ABSTRACT Most important, yet least understood, question, how microbial activity in soil under saline water irrigation responds to carbon (C) varying qualitatively (most labile form to extreme recalcitrant form) with or without maintaining C/N ratio was investigated in an incubation experiment. Soil samples from a long-term saline-water (electrical conductivity, EC ≈ 0, 6, and 12 dS m−1)- irrigated field were incorporated with three different C substrates, viz., glucose, rice straw (RS), and biochar with or without nitrogen (N as ammonium sulfate, NH4SO4) and were incubated at 25 °C for 56 days. Cumulative respiration (CR), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and dehydrogenase activity (DEA) concentrations decreased with increasing EC (P < 0.05), but less so in soils amended with glucose followed by RS and biochar. The addition of N to soils amended with different C substrates significantly decreased CR, MBC, DEA, and available phosphorus (P) concentrations at a given EC level.

Influence of Levels and Methods of Boron Application on the Yield and Uptake of Boron by Cotton in a Calcareous Soil of Punjab

ABSTRACT A field experiment was conducted to study the influence of boron (B) application on yield and B uptake of cotton (Gossypium hirsutum L.) in B-deficient calcareous soil of south-west Punjab. The treatments comprise six levels of soil-applied B (0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 mg B kg−1soil) and two levels of foliar-applied B (0.1% and 0.2% borax and granubor solution) along with the common control (no B application). The experiment was laid out in RBD factorial design with three replications. The seed cotton yield and its attributing characters (plant height, number of sympodial and monopodial branches, boll weight, and number of boll per plant) and root biomass increased significantly with increasing levels of boron up to 1.0 mg B kg−1 level over the control and then remained nonsignificant with further higher levels of soil-applied boron. Among foliar-applied boron levels, 0.1% borax solution was better than 0.2% borax solution. Soil-applied boron was at par with foliar-applied boron. The efficiency of borax and granubor was found to be equal in both sources of boron. The mean B content and its uptake by seed cotton and roots increased significantly up to 1.0 mg B kg−1 soil-applied B level and then recorded nonsignificant with further higher levels of boron. For the foliar method of B application, the mean B content and its uptake by seed cotton increased significantly over the control. The mean available B content in soils (0–15 cm) at 45, 75, 105, and 145 days after sowing increased significantly over the control for all soil-applied B levels, while it remained nonsignificant over the control for all growth stages of cotton in foliar method of B application. Further, it was positively correlated with root biomass (r = 0.91), boron uptake by root (r = 0.98), and sympodial branch per plant (r = 0.81). The interaction of B application levels and sources was not significant for all studied traits. Regardless of B sources, B application had a significant effect on yield, yield attributes, and B uptake up to 1.0 mg B kg−1 level for soil-applied B and 0.1% borax or granubor solution for foliar-applied B.