Nirmalendu Basak

Assessing soil-quality indices for subtropical rice-based cropping systems in India

Rice-based cropping systems are the foundation of food security in countries of Southeast Asia, but productivity of such systems has declined with deterioration in soil quality. These systems are different from other arable systems because rice is grown under submergence, and this may require a different set of key soil attributes for maintenances of quality and productivity. A minimum dataset was screened for assessing quality of soils belonging to three Soil Orders (Inceptisols, Entisols and Alfisols) by using statistical and mathematical models and 27 physical, chemical and biological attributes. Surface soils were collected from farmers’ fields under long-term cultivation of rice–potato–sesame cropping systems. Most of the attributes varied significantly among the Soil Orders used. Four or five key attributes were screened for each Soil Order through principal component and discriminate analysis, and these explained nearly 80% and 90% of the total variation in each Soil Order dataset. The attributes were dehydrogenase activity (DHA), available K, cation exchange capacity (CEC) and pHCa for Inceptisols; organic C, pHCa, bulk density, nitrogen mineralisation (Nmin) and β-glucosidase for Entisols; and DHA, very labile C, Nmin and microbial biomass C for Alfisols. Representation of the screened attributes was validated against the equivalent rice yield of the studied system. Among the selected key soil attributes, DHA and CEC for Inceptisols, organic C for Entisols, and Nmin and very labile C for Alfisols were most strongly correlated with system yield (R2 = 0.45, 0.77 and 0.78). Results also showed that biological and chemical attributes were most sensitive for indicating the differences in soil quality and have a strong influence on system yield, whereas soil physical attributes largely varied but did not predict system yield.

Organic Amendments Influence on Soil Biological Indices and Yield in Rice-Based Cropping System in Coastal Sundarbans of India

ABSTRACT The present investigation was carried out in coastal Sundarbans of India to study the effects of farm yard manure, green leaf manure, and vermicompost on biological attributes of soils and yield in rice–tomato, rice–sunflower, and rice–chili cropping system over conventional farmer’s practices (control) by a strip-plot technique for the two consecutive years. The partial substitution of inorganic fertilizers through organics significantly increased the yield of various cropping systems. The use of organic materials significantly improved microbial biomass carbon, fluorescein diacetate hydrolyzing activities, dehydrogenase, and β-glucosidase activity over control, which varied in the tune of 51.6%, 67.4%, 50%, and 62.7%, respectively, due to variation in electrical conductivity (EC) of these soils. The improved soil microbial biomass and enzyme activities act as key driving factor for organic matter decomposition and nutrient transformation in organically amended soils which lead to better yield under such cropping sequences.

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

ABSTRACT Organics, biological, and inorganic fertilizers play a crucial role for improving crop yield and soil properties. Accordingly, we assessed their impact on yield, microbial activities, and transformations of carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) in soils under a 12-year-old intensively cultivated rice (Oriza sativa L.), mustard (Brassica juncea L.), sesame (Sesamum indicum L.) system with sole inorganic (NPK); NPK + farmyard manure (NPKF); NPK + green manure (NPKG) (Sesbania sesban L.), and NPK + green manure + bio-fertilizer (NPKGB) (Azotobacter chroococcum+ pseudomonas putida) treatments in sub-tropical India. The system yield was much higher with NPKF (23%) and NPKGB (18%) than that with NPK. Organic supplementation had a favorable influence on soil microbial biomass C (Cmic), N (Nmic), and activities of extracellular enzymes. Results of principal component and multiple regression analyses showed significant influence of Cmic on system yield (R2 = 91, p = 0.001) and S availability (R2 = 62, p = 0.001). Similarly, mineralizable N and acid phosphatase could predict significantly soil available N (R2 = 85, p = 0.001) and P (R2 = 51; p = 0.001), respectively. Results thus indicated that integrated nutrient management (NPKF/G) improved system yield, nutrient accumulation, and microbial activities in soils.

Organic amendment influences soil quality in farmers’ field under rice-based cropping systems in Indo-gangetic plains of India

Indexing soil quality and identification of key soil indicators are essential for maintaining sustainability of agricultural soils. A minimum data set was developed for soils collected from farmers’ field under long-term rice-potato-sesame (R-P-S) and rice-wheat (R-W) cropping systems with NPK and NPK + organic amendment (FYM) under Alfisols in Indo-Gangetic Plains of India. Soil samples (40 geo-referenced) were collected at 0–0.20 m depth from the fields following the same cropping systems for the last ten years. The samples were analyzed for a large number of physical, chemical and biological attributes. The multivariate statistical analysis showed that out of the 38 attributes, organic C, aggregate ratio, microbial biomass C (Cmic), available zinc and β-glucosidase (β-glu) activity were screened as key indicators of soil quality for soils under R-P-S system; whereas, very labile C, mineralizable C and N (Cmin and Nmin), and β-glu activity were found as key indicators of soil quality for soils under R-W cropping system. The overall results indicated that oxidizable organic C and its labile fractions viz., very labile C, Cmic or Cmin and the C-cycle regulating enzyme viz., β-glu activity are the process based key master indicators for the assessment of soil quality. Application of organic amendment with inorganic fertilizer always maintained higher soil quality index for soils under long-term R-P-S and R-W cropping systems.

Soil carbon pools under long-term rice-wheat cropping system in Inceptisols of Indian Himalayas

ABSTRACT Knowledge about soil organic carbon (SOC) stock and its allocation into different pools is important for global food and environmental security. Accordingly, an attempt is made in the present study to investigate into the dynamics of SOC pools i.e. total soil organic carbon (TOC), oxidisable organic carbon (OC) and its different fractions viz. very labile (CVL), labile (CL), less labile (CLL) and non-labile (CNL) in soils under a 26 years old long-term experiment with rice (Oryza sativa L) – wheat (Triticum aestivum L) cropping system on Inceptisols under humid agro-climatic region of India with different soil management practices (control, 100% recommended dose of NPK, and 50% recommended dose of NPK + 50% N through farmyard manure (FYM). Of the several pools analyzed, a higher proportion of C was found in labile pool followed by very labile, non-labile, and less labile ones constituting about 46, 26.5, 20 and 7.3% of the total organic C at surface soil. The NPK+FYM treatment was found to have higher SOC pools, lability index (LI), recalcitrance indices and stratification ratio as compared to others. Results indicated that balanced fertilization with inorganic and organics is important for maintaining overall sustainability of the rice-wheat system.

Residual effect of crop residues on growth, yield attributes and soil properties of wheat under rice-wheat cropping system.

Residual effect of crop residues along with green manure, microbial culture and inorganic fertilizer on yield and soil properties of wheat grown after rice were studied. The following treatments such as control, straw burn (5 t ha−1), straw incorporation (5 t ha−1), straw (5 t ha−1) + 25% N of recommended dose, straw (5 t ha−1) + green manure (5 t ha−1) and straw (5 t ha−1) + microbial culture (a cocktail of Aspergillus, Trichoderma, Pleurotus and Phanerochaete) were imposed on rice and their residual effects on the yield of wheat and nutrients content in soils were evaluated. Results showed that application of straw (5 t ha−1) + green manure (5 t ha−1) recorded the highest yield of wheat followed by the straw (5 t ha−1) + 25%N of recommended dose > straw (5 t ha−1) + microbial culture > straw incorporation (5 t ha−1) > straw burn (5 t ha−1) > control. Availability of soil nutrients particularly N, P, K and organic carbon also increased following the above trend.

Influence of organic amendments on soil physical attributes and aggregate associated phosphorus under long-term rice-wheat cropping

Abstract The quantification of phosphorus (P) in bulk soil and P distribution in different size fractions of water-stable aggregates (WSAs) are important for assessing potential P loss through runoff. We evaluated available and total P distribution within WSAs of a sitty clay to clay soil in a long-term fertility experiment of a rice-wheat cropping system in India. Surface soil samples were collected from seven plots amended with NPK fertilizers in combination with or without organic amendments, farmyard manure (FYM), green manure (GM), and paddy straw (PS). The plot with no NPK fertilizers or organic amendments was set as a control. The soil samples were separated by wet sieving into four soil aggregate size fractions: large macroaggregates (> 2.0 mm), small macroaggregates (0.25–2.0 mm), fine microaggregates (0.05–0.25 mm), and a silt + clay-sized fraction ( small macroaggregates > fine microaggregates > large macroaggregates. Within a size class, aggregate-associated available and total P contents in the organically amended soil were in the following order: FYM > PS ≥ GM. The available P content of the microaggregates ( 0.25 mm), and the total P content of the microaggregates was 4- to 5-times higher than that of the macroaggregates. Cultivation without organic amendments resulted in more microaggregates that could be checked by the application of organic amendments such as FYM and GM, which increased the proportion of water-stable macroaggregates by consolidating microaggregates into macroaggregates.