T. J. Purakayastha

Influence of vesicular-arbuscular mycorrhizal fungi (Glomus etunicatum L.) on mobilization of zinc in wetland rice (Oryza sativa L.)

Abstract. In a greenhouse trial, rice (Oryza sativa L.) cultivar Pusa Basmati-1 was grown in a Zn-deficient Typic Ustochrept soil from IARI farm, New Delhi, India. The experimental design included two rates of inoculation with vesicular-arbuscular mycorrhizal fungi (VAMF), Glomus etunicatum (nil and inoculated) and different combinations of organic (farmyard manure, FYM) and inorganic (NPK, ZnSO4) fertilizers. The results revealed that a high intensity of root colonization in rice inoculated with G. etunicatum could be achieved by raising seedlings in P- and Zn-deficient soil in the nursery under aerobic conditions. Moreover, the VAMF that infected rice seedlings in the nursery also survived when the same seedlings were transplanted into pots under waterlogged conditions. The application of ZnSO4 significantly increased the inflow of Zn to rice roots at the panicle-initiation stage (40xa0days after transplanting) relative to NPK. The former treatment also increased root length, root weight, root volume and total uptake of Zn and thereby increased the grain and dry matter yields. Alternatively, these variables were substantially enhanced by inoculating rice with the VAMF, G. etunicatum. The VAMF-colonized rice plants were more active in acquiring Zn from either added or native sources than non-colonized plants, and consequently the available-Zn content in soil was lower after the harvest of rice.

Phytoextraction of arsenic contaminated soil by Chinese brake fern (Pteris vittata): Effect on soil microbiological activities

A greenhouse experiment was conducted to investigate the effect of phytoextraction by Chinese brake fern (Pteris vittata L.) on microbial activity and biomass in arsenic-contaminated soil (naturally occurring arsenic-contaminated soils of West Bengal, India). P. vittata was grown for two successive growing cycles (4xa0months each) with two phosphate sources (di-ammonium phosphate (DAP) and single superphosphate (SSP)). After phytoextraction by P. vittata, the rhizosphere soils were analyzed for microbial biomass C (MBC), C mineralization (Cmin), dehydrogenase activity (DHA), phosphomonoesterase activities, and aryl sulphatase activity. All enzyme activities increased after two successive growing cycles of P. vittata as compared to one growing cycle and unplanted control. The arsenic (As) phytoextraction by this fern also increased the MBC by 34xa0%, Cmin by 63xa0%, DHA by 38xa0%, acid phosphomonoesterase activity by 30xa0%, alkaline phosphomonoesterase activity by 6xa0%, and aryl-sulphatase activity by 33xa0% with two successive growing cycles over unplanted control. The di-ammonium phosphate was better as compared to single super phosphate for enhancing microbiological and biochemical parameters except phosphomonoesterase activities.

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.

Growth and iron nutrition of broccoli (Brassica oleracea L. var. Italica Plenck), grown in a Typic Ustochrept, as influenced by vesicular-arbuscular mycorrhizal fungi in the presence of pyrite and farmyard manure

Abstract Greenhouse experiments were conducted using potted soil (Fe-deficient Typic Ustochrept) to study the influence of the vesicular-arbuscular mycorrhizal fungi (VAM), Glomus macrocarpum and G. fasciculatum, on the mobilisation of Fe in broccoli (Brassica oleracea L. var. italica Plenck) in the presence of pyrite and farmyard manure (FYM). Individual applications of either VAM or pyrite with NPK fertiliser significantly enhanced both the Fe2+ content in leaf tissue and total uptake of Fe and resulted in increased curd and straw yields of broccoli compared to those observed with NPK alone. Though the application of FYM decreased the Fe2+ content in leaf tissue relative to plants supplied NPK alone, this result was not statistically significant. The available Fe content in soil, after harvest of broccoli, was found to be lower in the presence of VAM than in the control.

Effect of humic acid multinutrient fertilizers on yield and nutrient use efficiency of potato

ABSTRACT A field experiment was conducted to study the effect of humic acid multinutrient fertilizers like Grow Flow 45H and HA-NPK complex on crop yield, nutrient content and uptake, and nutrient use efficiency of potato. Application of Grow Flow 45H (humic acid multinutrient liquid fertilizer) at recommended dose increased the tuber yield by 9.3% as compared to chemical fertilizer. Nitrogen (N), phosphorus (P) and potassium (K) content of the Grow Flow 45H treated plants were 2.89, 0.33 and 1.58% in shoots and 1.89, 0.21 and 1.03% in tubers, respectively which were significantly higher than the other treatments. Grow Flow 45H increased the N, P and K use efficiencies by 16.4%, 9.3% and 18.3% respectively over chemical fertilizer. Though HA-NPK complex fertilizer (developed in the laboratory) was not significantly different from chemical fertilizer in respect of yield, the contents and uptake, and use efficiencies of N, P and K; however the former was found better than the latter.

Microbial biomass phosphorus and alkaline phosphomonoesterase activity in the rhizosphere of different wheat cultivars as influenced by inorganic phosphorus and farmyard manure

Wheat cultivars C 306, PBW 175, HD 1553, and HD 2329 were grown in an alkaline soil with and without inorganic P fertilizer and/or farmyard manure in a pot culture experiment. Microbial biomass P (MBP) and alkaline phosphomonoesterase (APM) activities were studied in rhizosphere soils of the above wheat cultivars at different physiological stages. Root weight and P uptake were also estimated simultaneously. Higher microbial biomass P was observed at crown root initiation (CRI) stage while APM activities were higher at panicle initiation (PI) stage. The HD cultivars showed higher MBP and APM activities at PI stage, while at CRI stage, the reverse was true. Though the application of inorganic P apparently showed higher APM activity, the ratio of APM activity and microbial biomass P (APM to MBP) decreased in the presence of inorganic fertilizer P. Inorganic P compared to FYM was the more dominant factor in reducing the APM to MBP ratio. Root weight did not correlate with grain yield. From step-wise regression analysis, it was revealed that microbial biomass P at both CRI and PI stages was a significant factor in influencing the P uptake in relation to grain yield of wheat.