Ashok K. Patra

Pedotransfer functions for predicting the hydraulic properties of Indian soils

Most of the data pertaining to Indian soils are limited to the major soil separates, sand, silt, and clay. We examined the possibilities of using these parameters to describe the hydraulic characteristics of the soils of India. The final or steady-state infiltration rate, which is mainly profile-controlled, showed a power function relationship with the maximum and the average clay content in the soil profile. The saturated hydraulic conductivity also showed a similar relationship with the silt + clay content. The soil water content at a given suction could be satisfactorily predicted using the percentage of major soil separates, sand, silt, and clay. The coefficients in the soil water function ψ(θ) were linearly related to the sand content. Non-linear regression equations were developed to predict these coefficients using the percentages of sand and clay in soils. The equations proved to be quite satisfactory for a wide range of textures and provided reasonably accurate estimates of the soil water characteristic curve from a minimum of readily available data.

PHYTOREMEDIATION OF ARSENIC CONTAMINATED SOIL BY PTERIS VITTATA L. I. INFLUENCE OF PHOSPHATIC FERTILIZERS AND REPEATED HARVESTS

A greenhouse experiment was conducted to evaluate the effectiveness of diammonium phosphate (DAP), single superphosphate (SSP) and two growing cycles on arsenic removal by Chinese Brake Fern (Pteris vittata L.) from an arsenic contaminated Typic Haplustept of the Indian state of West Bengal. After harvest of Pteris vittata the total, Olsens extractable and other five soil arsenic fractions were determined. The total biomass yield of P. vittata ranged from 10.7 to 16.2 g pot−1 in first growing cycle and from 7.53 to 11.57 g pot−1 in second growing cycle. The frond arsenic concentrations ranged from 990 to 1374 mg kg−1 in first growing cycle and from 875 to 1371 mg kg−1 in second growing cycle. DAP was most efficient in enhancing biomass yield, frond and root arsenic concentrations and total arsenic removal from soil. After first growing cycle, P. vittata reduced soil arsenic by 10 to 20%, while after two growing cycles Pteris reduced it by 18 to 34%. Among the different arsenic fractions, Fe-bound arsenic dominated over other fractions. Two successive harvests with DAP as the phosphate fertilizer emerged as the promising management strategy for amelioration of arsenic contaminated soil of West Bengal through phyotoextraction by P. vittata.

Soil carbon pools and carbon management index under different land use systems in the Central Himalayan region

Abstract We investigated different land use and cropping systems in the Almora region of Central Himalaya to assess total organic carbon (TOC), microbial biomass carbon (MBC), particulate organic carbon (POC), labile carbon (LC), microbial quotient (MQ) (i.e., ratio of MBC to TOC) and measured the carbon management index (CMI). The TOC content recorded the highest value in undisturbed forest (45.4 g kg−1 soil) and lowest in barren land (18.4 g kg−1 soil). The MBC values varied from 146 mg kg−1 in barren land to 783 mg kg−1 in undisturbed oak forest. Land under organic farming showed higher LC values (4.0 g kg−1) than soya bean–wheat and fodder crops. The average POC values ranged from 0.9 g kg−1 in barren land to 11.0 g kg−1 in undisturbed oak forest. Variation of these parameters with season and depth was also observed. The CMI was highest under the forest ecosystem and lowest in barren land. Our study thus revealed that cultivation of Himalayan soils has significantly reduced the soil organic carbon pools and thus maintenance of natural forest or eco-friendly practices such as inclusion of legumes and application of organics is urgently needed for sustainable use of these ecosystems.

Surface tailored organobentonite enhances bacterial proliferation and phenanthrene biodegradation under cadmium co-contamination.

Co-contamination of soil and water with polycyclic aromatic hydrocarbon (PAH) and heavy metals makes biodegradation of the former extremely challenging. Modified clay-modulated microbial degradation provides a novel insight in addressing this issue. This study was conducted to evaluate the growth and phenanthrene degradation performance of Mycobacterium gilvum VF1 in the presence of a palmitic acid (PA)-grafted Arquad® 2HT-75-based organobentonite in cadmium (Cd)-phenanthrene co-contaminated water. The PA-grafted organobentonite (ABP) adsorbed a slightly greater quantity of Cd than bentonite at up to 30mgL(-1) metal concentration, but its highly negative surface charge imparted by carboxylic groups indicated the potential of being a significantly superior adsorbent of Cd at higher metal concentrations. In systems co-contained with Cd (5 and 10mgL(-1)), the Arquad® 2HT-75-modified bentonite (AB) and PA-grafted organobentonite (ABP) resulted in a significantly higher (72-78%) degradation of phenanthrene than bentonite (62%) by the bacterium. The growth and proliferation of bacteria were supported by ABP which not only eliminated Cd toxicity through adsorption but also created a congenial microenvironment for bacterial survival. The macromolecules produced during ABP-bacteria interaction could form a stable clay-bacterial cluster by overcoming the electrostatic repulsion among individual components. Findings of this study provide new insights for designing clay modulated PAH bioremediation technologies in mixed-contaminated water and soil.

Soil Pollution - An Emerging Threat to Agriculture

Agriculture has always remained backbone of economy and sociopolitical stability of low and middle income countries, and employs largest work force in India. Maintenance of soil quality has been pointed out as one of the major contributing factors for sustainability of agricultural production. Rising contribution of industry to India’s GDP has been speculated to cause adverse impact on the precious land resources; though the issue has received less attention among the policy makers. There is a complex relationship of Indian economy with industry and agriculture, both of which competing for same natural resources with differential impact on land resources. This chapter highlights the need for reviewing different developmental activities having direct or indirect impact on agricultural productivity and the need for accelarating soil research to investigate upon migration of pollutants from source of generation and their impact on soil so as to devise strategies for protection and remediation of precious non-renewable soil resources.

Phytoremediation of Arsenic Contaminated Soil by Pteris Vittata L. II. Effect on Arsenic Uptake and Rice Yield

A greenhouse experiment evaluated the effect of phytoextraction of arsenic from a contaminated soil by Chinese Brake Fern (Pteris vittata L.) and its subsequent effects on growth and uptake of arsenic by rice (Oryza sativa L.) crop. Pteris vittata was grown for one or two growing cycles of four months each with two phosphate sources, using single super phosphate (SSP) and di-ammonium phosphate (DAP). Rice was grown on phytoextracted soils followed by measurements of biomass yield (grain, straw, and root), arsenic concentration and, uptake by individual plant parts. The biomass yield (grain, straw and rice) of rice was highest in soil phytoextracted with Pteris vittata grown for two cycles and fertilized with diammonium phosphate (DAP). Total arsenic uptake in contaminated soil ranged from 8.2 to 16.9 mg pot−1 in first growing cycle and 5.5 to 12.0 mg pot−1 in second growing cycle of Pteris vittata. There was thus a mean reduction of 52% in arsenic content of rice grain after two growing cycle of Pteris vittata and 29% after the one growing cycle. The phytoextraction of arsenic contaminated soil by Pteris vittata was beneficial for growing rice resulted in decreased arsenic content in rice grain of <1 ppm. There was a mean improvement in rice grain yield 14% after two growing cycle and 8% after the one growing cycle of brake fern.

Long-term effects of different land use and soil management on various organic carbon fractions in an Inceptisol of subtropical India

Land use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical regions, can potentially alter soil C dynamics. A study was conducted to assess the effects of various land uses and soil managements (agro-forestry plantation, vegetable field, tube-well irrigated rice-wheat, sewage-irrigated rice-wheat, and uncultivated soils) on soil pH, bulk density, soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), C mineralisation (Cmin), microbial quotient, and microbial metabolic quotient (q CO2 ) in 0-0.05, 0.05-0.10, and 0.10-0.20 m soil depths. At 0-0.05 m, the bulk density was lowest (1.29 Mg/m 3 ) in agro-forestry soil, whereas the uncultivated soil (jointly with vegetable field soil) showed highest bulk density (1.48 Mg/m 3 ). Sewage-irrigated rice-wheat soil showed lowest pH particularly in the 0-0.05 and 0.10-0.20 m soil layer. Irrespective of soil depths, agro-forestry plantation showed greater SOC followed by sewage-irrigated rice-wheat soil. Nevertheless, agro-forestry soil also showed highest stock of SOC (33.7 Mg/ha), POC (3.58 Mg/ha), and MBC (0.81 Mg/ha) in the 0-0.20 m soil layer. Sewage-irrigated rice-wheat jointly with agro-forestry soil showed greatest Cmin in the 0-0.20 m soil layer, although the former supported lower SOC stock. The decrease in SOC (SOC0-0.05 m/SOC0.10-0.20 m) and Cmin (Cmin 0-0.05 m/Cmin 0.10-0.20 m) along soil depth was significantly higher in the agro-forestry system than in most of the other land use and soil management systems. Microbial quotient was highest in sewage-irrigated rice-wheat soil, particularly in the 0-0.05 m soil depth, whereas q CO2 was greater in uncultivated soil. In general, microbial quotients decreased, whereas q CO2 increased down the soil profile.

Balanced Fertilization along with Farmyard Manures Enhances Abundance of Microbial Groups and Their Resistance and Resilience against Heat Stress in a Semi-arid Inceptisol

The impact of long-term (36-year) application of balanced fertilizers and farmyard manures (FYM) on the abundance of microbial groups (bacteria, fungi, actinomycetes, Pseudomonas, Azotobacter, ammonia-oxidizing bacteria) and their resistance and resilience against heat stress was investigated in a semi-arid Inceptisol at New Delhi, India. Surface soils from selected treatments [control, nitrogen (N), N and phosphorus (P), NP and potassium (K), NPK + FYM] under a maize crop were assessed immediately after sampling (0-day) and at 1, 14, 28, and 56 day(s) after heat stress (48 °C for 24 h). The heat stress significantly reduced the microbial groups by 20 to 80%. Recovery after stress was 60 to 100% within 56 days. Resistance and resilience of fungi and actinomycetes were greater than other groups of organisms. Ammonia-oxidizing bacteria (AOB) were found to be most sensitive with the lowest resistance index. Application of NPK + FYM was most effective in enhancing the resistance and resilience of soil microorganisms against heat stress.

Assessment of microbial biomass and enzyme activities in soil under temperate fruit crops in north western himalayan region

Microbial communities are important for the functioning of the ecosystem, both in relation to direct interactions with the plants and with regard to nutrient and organic matter recycling. A study in field condition was undertaken in Kashmir valley to reveal the effect of various temperate fruit crops viz. apricot, peach, plum and cherry along with a control (no-plantation) on microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP) and dehydrogenase, phosphomonoesterase (acid and alkaline) and urease activities in soil at two different depths (0-20 and 21-40 cm). All the fruit crops showed a sharp decline in microbial biomass and enzyme activities with the increase in soil depth. Each of the four fruit crops showed significant (p<0.05) impact on MBC over the control and the maximum MBC was recorded in plum (1000 mg kg-1) and the lowest value was observed in control (457 mg kg-1), at the surface layer. Since there is a relationship between MBC and MBN, the similar trend was also observed in MBN as in case of MBC. For MBP, fruit crops showed any significant effect neither on surface soil, nor on subsurface soil layer over control. At the surface layer, unlike microbial biomass the highest dehydrogenase activity was observed in peach (318 mg TPF g soil-1 h-1) and the lowest value (166 mg TPF g soil-1 h-1) was attained at control plot. Maximum alkaline phosphomonoesterase activity was observed in peach (381 mg PNP g soil-1 h-1), although for acid phosphomonoesterase the highest value recorded in apricot (306 mg PNP g soil-1 hr-1), at surface soil. A significant positive correlation (p <0.01) was observed amongst MBC, MBN and MBP. Both the phosphomonoesterase activities were significantly (p <0.05) correlated with MBP in soil. It can be concluded that the influence of the studied fruit crops on the soil was not uniform, in terms of the measured parameters.

Enhancing Crop Productivity in Salt-Affected Environments by Stimulating Soil Biological Processes and Remediation Using Nanotechnology

World food production systems primarily crop lands are set to face unprecedented stress for matching production with overwhelming population growth in the backdrop of increasing natural calamities and climate change. Another green revolution does not seem likely with the same approaches as followed in the past. A large extent of marginally productive lands (including salt affected) in India and the world presents opportunity for bolstering food security via land reclamation, improved productivity, and resource conservation by enhancing biological functions of soil. The presence of soluble salts in the soil and water, including surface water and groundwater, poses great threat to productivity of land. Land use practices, such as clearing and irrigation, have significantly increased the extent of the problem. The most obvious effect of salts in soil includes decline in agricultural productivity. High concentrations of salt in the soil are toxic to plants, restrict plant uptake of water, and prevent plants from taking up essential nutrients. There are several approaches to manage these lands including chemical reclamation, but they are very resource expensive. Nanotechnology as an emerging science may play a greater role for managing these salt-affected marginal lands. Though nanotechnology, in respect of both research and development, is as yet at a nascent stage, it can be effectively directed toward understanding and creating improved materials, devices, and systems and in exploiting the nano-properties for managing these lands. Nanotechnology has not left agricultural sector untouched and promises to revolutionize the agricultural sector with new tools for molecular treatment of plant diseases, rapid detection of diseases, and enhancing the ability of plant to absorb nutrients, thus increasing soil fertility and crop production. The potential of nanotechnology is yet to be fully exploited in salt-affected land management, and agriculture, yet if once realized, it is likely to bring a sea change in agricultural production and productivity.