Gora Chand Hazra

Distribution of zinc fractions and their transformation in submerged rice soils

Distribution of different forms of Zn in 16 acid alluvial rice growing soils of West Bengal (India) and their transformation on submergence were studied. The results showed that more than 84% of total Zn occurred in the relatively inactive clay lattice-bound form while a smaller fractionviz. 1.1, 1.6, 11.1 and 2.0 per cent of the total occurred as water-soluble plus exchangeable, organic complexed, amorphous sesquioxide-bound and crystalline sesquioxide bound forms, respectively. All these four Zn forms showed significant negative correlations with soil pH (r=−0.48**, −0.39*, −0.61** and −0.67**, respectively), while the latter two Zn forms showed significant positive correlations with Fe2O3 (0.68** and 0.88***) and Al2O3 (0.89*** and 0.75***) content of the soils. The different Zn forms were found to have positive and significant correlations amongst each other, suggesting the existence of a dynamic equilibrium of these forms in soil.Submergence caused an increase in the amorphous sesquioxide-bound form of Zn and a decrease in each of the other three forms. The magnitude of such decreases in water-soluble plus exchangeable and crystalline sesquioxide-bound forms was found to be correlated negatively with initial pH values of the soils and positively with the increase in the amorphous sesquioxide-bound form, indicating their adsorption on the surface of the freshly formed hydrated oxides of Fe, which view was supported by the existence of significant positive correlation between the increase in the amorphous sesquioxide-bound form of Zn and that in AlCl3-extractable iron. The existence of a positive correlation between the decrease in crystalline sesquioxide-bound Zn and that in Fe2O3 content in soil suggested that on waterlogging the soil Zn occluded in the cry talline sesquioxide was released as a result of reduction of Fe2O3.

Zinc adsorption in soils as influenced by different soil management practices

Zinc adsorption was studied in four soils (two Alfisols and two Inceptisols) under three different moisture regimens, viz., flooded-drying (FD), alternate wetting and drying (AWD), and preflooding (PF), each with and without added organic matter (0.50 and 0%). Results showed that the FD and AWD moisture treatments caused a marked decrease, whereas the PF treatment caused a marked increase, in the magnitude of Zn adsorption by the soils compared with controls (no moisture and no organic matter treatment). When organic matter was combined with all three moisture regime treatments, however, there was a significant increase in Zn adsorption compared with the no-organic matter control. Other adsorption-related parameters of the soils, such as adsorption maxima, bonding energy constant, free energy change for Zn, and Zn-hydroxide potential, affirmed the pattern of changes in Zn adsorption following such treatments. All such changes have been explained on the basis of the changes in soil physico-chemical properties, viz., pH, CaCO 3 equivalent, and Fe oxides as a result of treatments. Amorphous Fe oxides and soil pH were, however, found to play a major role in this regard. Results indicated the need for split application of Zn under AWD and FD regimes, but the reverse is true under PF treatments.

EFFECT OF PREFLOODING ON TRANSFORMATION OF APPLIED ZINC AND ITS UPTAKE BY RICE IN LATERITIC SOILS

Lateritic soils usually contain high amounts of oxides of iron, which are known to have strong zinc-binding capacity. When such soils are used for growing flooded rice and zinc is used as fertilizer, much of it is likely to be fixed by oxides of iron if it is applied immediately after flooding the soil. But if such application of zinc is made after keeping these soils preflooded for a few days, its fixation may be lowered due to the changes occuring in the oxides of iron during the preflooding period. Keeping the above in view we investigated the effect of different periods (0 and 15 d) of preflooding on the transformation of applied zinc in four lateritic ricegrowing soils into its different forms, namely (i) water soluble plus exchangeable (WSEX), (ii) organically complexed (OC), (iii) manganese oxide bound (MnOX), (iv) amorphous iron oxide bound (AMOX), and (v) crystalline oxide bound (CRYOX). Results showed that the transformation of applied zinc into WSEX, OC and AMOX forms was more, and that transformation into MnOX and CRYOX forms was less, when zinc was applied after keeping the soils preflooded for 15 days as compared to such transformation when zinc was applied immediately after flooding (0 d preflooding). This was found to be related to the changes in the forms of oxides of iron and manganese during the period of preflooding. Results of a greenhouse experiment showed that uptake of applied zinc by rice was more when it was applied after 15 d than after 0 d preflooding. Results suggest that use efficiency of applied zinc for rice in lateritic soils can be improved if its application is delayed by 15 d after flooding the soils.

Nitrate and fluoride contamination in groundwater of an intensively managed agroecosystem: A functional relationship

A study was conducted to assess the potential of nitrate-nitrogen (NO(3)-N) and fluoride (F) contamination in drinking groundwater as a function of lithology, soil characteristics and agricultural activities in an intensively cultivated district in India. Two hundred and fifty two groundwater samples were collected at different depths from various types of wells and analyzed for pH, electrical conductivity (EC), NO(3)-N load and F content. Database on lithology, soil properties, predominant cropping systems, fertilizer and pesticide uses were also recorded for the district. The NO(3)-N load in groundwater samples were low ranging from 0.12 to 6.58 microg mL(-1) with only 8.7% of them contained greater than 3.0 microg mL(-1) well below the 10 microg mL(-1), the threshold limit fixed by WHO for drinking purpose. Samples from the habitational areas showed higher NO3-N content over the agricultural fields. The content decreased with increasing depth of wells (r=-0.25, P< or =0.01) and increased with increasing rate of nitrogenous fertilizer application (r=0.90, P< or =0.01) and was higher in areas where shallow- rather than deep-rooted crops (r=-0.28, P< or =0.01, with average root depth) are grown. The NO3-N load also decreased with increasing bulk density (r=-0.73, P< or =0.01) and clay content (r=-0.51, P< or =0.01) but increased with increasing hydraulic conductivity (r=0.68, P< or =0.01), organic C (r=0.78, P< or =0.01) and potential plant available N (r=0.82, P< or =0.01) of soils. Fluoride content in groundwater was also low (0.02 to 1.15 microg mL(-1)) with only 4.0% of them exceeding 1.0 microg mL(-1) posing a potential threat of fluorosis. On average, its content varied little spatially and along depth of sampling aquifers indicating little occurrence of F containing rocks/minerals in the geology of the district. The content showed a significant positive correlation (r=0.234, P=< or =0.01) with the amount of phosphatic fertilizer (single super phosphate) used for agriculture. Results thus indicated that the groundwater of the study area is presently safe for drinking purpose but some anthropogenic activities associated with intensive cultivation had a positive influence on its loading with NO(3)-N and F.

Transformation of zinc in soils under submerged condition and its relation with zinc nutrition of rice

Laboratory and greenhouse experiments were conducted with two soilsviz., laterite and alluvial to study the transformation of applied Zn in soil fractions under submerged condition in the presence and absence of added organic matter and its relationship with Zn nutrition of rice plants.The results showed that application of organic matter caused a decrease in the concentration of Zn in shoot and root of rice plants and helped in translocating the element from root to shoot. The per cent utilization of applied Zn by plants was also found to increase by the application of organic matter. The transformation of applied Zn in different fractions in soils showed that a major portion (53.6–72.6%) of it found its way to mineral fractions leaving only 1.0–3.3, 6.6–18.9, 11.0–21.6 and 2.3–8.8% of the applied amounts in water soluble plus exchangeable, organic complexed, amorphous sesquioxides and crystalline sesquioxides bound fractions respectively. Application of organic matter favoured such transformation of applied Zn into these fractions except the mineral and crystalline sesquioxides bound ones.Simple correlation and multiple regression analyses between applied Zn in different soil fractions and fertilizer Zn content in plants showed that organic matter application increased the predictability of fertilizer Zn content in plants which has been attributed to the higher per cent recovery of applied Zn in plant available fractions in soils in presence of added organic matter.

DEPTHWISE DISTRIBUTION OF COPPER FRACTIONS IN SOME ULTISOLS

We studied the depthwise distribution of different forms of Cu, namely water soluble + exchangeable (WSEX), organically complexed (OC), MnO2 (MnOX), amorphous Fe-oxides (AMOX), and crystalline Fe-oxides (CRYOX) bound in 12 Ultisols of West Bengal, India. On an average, the OC, AMOX and CRYOX forms accounted for 20, 19, and 13%, respectively, of the total Cu in the surface soils (0–15 cm), while the WSEX and MnOX forms constituted only negligible fractions, accounting for 2.0 and 0.4% of the total amount. With depth, the content in the OC, AMOX, and WSEX forms recorded a decrease, while that in the MnOX and CRYOX forms recorded an increase. Such increase/decrease has been explained by the variations in the content of organic C, Mn-oxide, and amorphous and crystalline Fe oxide content in the different layers of soils. Significant correlations were obtained between WSEX-Cu versus pH (r = −0.47**), OC-Cu versus organic C (r = 0.78**) and amorphous Fe oxide (r = 0.44**), and AMOX-Cu versus organic C (r = 0.46**) and amorphous Fe oxide (r = 0.48**). The different Cu forms also showed significant correlation amongst themselves, suggesting the existence of a dynamic equilibrium. Simple correlation, multiple regression, and pathcoefficient analyses indicated that the WSEX-, OC-, and AMOX-Cu played the most important role in maintaining the available Cu pool in these soils.

Effect of Silicon Fertilization on Growth, Yield, and Nutrient Uptake of Rice

ABSTRACT A field experiment was conducted to study the effect of silicon (diatomaceous earth, DE) fertilization on growth, yield, and nutrient uptake of rice during the kharif season of 2012 and 2013 in the new alluvial zone of West Bengal, India. Results showed that application of silicon significantly increased grain and straw yield as well as yield-attributing parameters such as plant height (cm), number of tillers m−2, number of panicle m−2, and 1000-grain weight (g) of rice. The greatest grain and straw yields were observed in the treatment T6 (DE at 600 kg ha−1 in combination with standard fertilizer practice (SFP). The concentration and uptake of silicon, nitrogen (N), phosphorus (P), and potassium (K) in grain and straw were also greater under this treatment compared to others. It was concluded that application of DE at 600 kg ha−1 along with SFP resulted increased grain, straw, and uptake of NPK.

Nutrient Management, Energy Input–Output, and Economic Analyses of Eggplant Production Under Subtropical Conditions

ABSTRACT Energy input–output and cost analyses of production contribute to cost-effective management of input resources to improve productivity and profitability. The input–output energy balance and economics of eggplant (Solanum melongena L.) production under 15 nutrient management (NM) practices, which included a control (normal farmer’s production practice), organic (cow manure, vermicompost, or mustard oil cake), inorganic fertilization (recommended NPK at 100N–22P–42K kg·ha−1 and 150% of recommended NPK), and selected combinations, were analyzed. A complete account of energy inputs consumed, energy output produced, cost of production, and gross return was determined under each NM technology and these data were used to calculate energy efficiency and profitability. On average, fertilizer application ranked first in energy consumption (13.80 GJ·ha−1); the least energy (0.71 GJ·ha−1) was required for transplanting seedlings. Integrated NM technologies were more energy efficient, and more profitable, than inorganic and organic ones alone. For eggplant production 3 Mg·ha−1 vermicompost plus 150% of recommended NPK was the highest net energy gainer (110.5 GJ·ha−1) and most profitable with a maximum net return (INR 219,343·ha−1; INR is Indian rupees, US

Assessment of Nutrient Management Technologies for Broccoli to Improve Productivity and Quality and Soil Resources in the Subtropics

1 = 66 INR), highest benefit–cost ratio (3.4), and fairly high marginal rate of return (8.8). Organic technologies required less energy and were less profitable. Among organics, the highest energy-conserving efficiency and maximum profit were obtained with cow manure. Balanced fertilization with integrated sources of nutrients is the most energy-efficient management option for productive and profitable eggplant production under subtropical conditions.

Impact of Long-Term Application of Organics, Biological, and Inorganic Fertilizers on Microbial Activities in Rice-Based Cropping System

ABSTRACT Assessment of nutrient management (NM) technologies for sustainable crop production requires a detailed understanding of the entire production system and how it affects quantity and quality of the yield, economic profitability, energy balance, environmental health, and soil quality. The influence of NM technologies on broccoli (Brassica oleracea L. var. italica Plenk) productivity and quality and effects on soil were determined. Fifteen NM technologies including a control (farmer’s production practice with 80N–15P kg·ha−1 of fertilizer); organics (vermicompost, cow manure, and mustard oil cake); inorganic fertilizer (recommended N–P–K at the rate of 150–33–63 kg ha−1 and 125% of recommended N–P–K [N–P–K^]); and their selected combinations were tested. Cow manure at 6.25 Mg·ha−1 + 125% of recommended N–P–K outperformed others with higher curd yield (11.4 Mg·ha−1), greater energy efficiency (net energy 39 GJ·ha−1; output–input energy ratio 2.77), higher economic return (benefit–cost ratio 8.7; marginal rate of return 25.3), and greater soil (2.65) and crop quality index (9.80). Organics used alone or in combinations were less productive, energetically less efficient, and less profitable compared to inorganic or integrated NM practices for growing broccoli under hot, humid, subtropical conditions.