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Rice is a staple food for about 65% of the India's population. India ranks first in area under rice and second in production of rice in the world. In India, it is cultivated over 43.39 m ha with a production and productivity of 104.32 million tons and 2404 kg/ha, respectively. Besides ensuring food security of the nation, it is an export commodity and earns a huge foreign exchange. In this study, we investigated the efficacy of five fungicides against Rhizoctonia solani Kuhn AG-1 IA, inciting sheath blight of rice in vitro and under field conditions along with post-harvest residue of the fungicides found effective in disease management. In vitro growth inhibition tests revealed that the EC values of azoxystrobin 18.2% + difenoconazole 11.4% SC, pencycuron 22.9% SC, thifluzamide 23.9% SC, hexaconazole 4% + zineb 68% WP, and validamycin 3% L against Rhizoctonia solani ranged from 0.006 to 354.81 ppm a.i., whereas the corresponding EC values were 0.758 to 1202.26 ppm a.i. Thifluzamide 23.9% SC was found to be the most inhibitory with EC and EC values of 0.006 and 0.758 ppm a.i. followed by hexaconazole 4% + zineb 68% WP. The complete inhibition of sclerotia formation was observed at 1 ppm, 20 ppm, and 25 ppm a.i. of thifluzamide 23.9% SC, hexaconazole 4% + zineb 68% WP, and azoxystrobin 18.2% + difenoconazole 11.4% SC, respectively. In field trials, azoxystrobin 18.2% + difenoconazole 11.4% SC was the best treatment in reducing sheath blight and in enhancing grain yield of rice followed by thifluzamide 23.9% SC, pencycuron 22.9% SC, and validamycin 3% L, whereas hexaconazole 4% + zineb 68% WP was the least effective fungicide. Benefit-cost ratio (B:C) of different fungicides reflected that pencycuron 22.9% SC (B:C 5.06) and azoxystrobin 18.2% + difenoconazole 11.4% SC(B:C 4.65) sprayed at single/recommended doses of 1 ml/l were highly economical in managing sheath blight disease of rice. Double dose of pencycuron 22.9% SC further enhanced the B:C to 7.24 while the double dose of azoxystrobin 18.2% + difenoconazole 11.4% SC was less economical (B:C 2.84) compared to their recommended doses. Samples of rice matrices were processed using QuEChERS method and analyzed for the presence of fungicide residues by gas chromatography-tandem mass spectrometry (GC-MS/MS). The post-harvest residues of azoxystrobin, difenoconazole, and pencycuron, sprayed at single/recommended and double doses with a pre-harvest interval (PHI) of 44 days, were found below the limit of quantification (LOQ), i.e., 0.01 and 0.005 mg kg for azoxystrobin and difenoconazole and 0.05 mg kg for pencycuron in brown rice, cropped soil, paddy straw, and husk. These results clearly demonstrated that treatment of azoxystrobin 18.2% + difenoconazole 11.4% SC and pencycuron 22.9% SC could be taken as safe for crop protection and environmental contamination point of view. The findings of this research work will have a positive impact on rice export and use.

Identificación y caracterización de fitopatógenos asociados al cultivo de X gulupa (Passiflora edulis f. edulis Sims) en el departamento de Antioquia Identification and characterization of phytopathogens associated with gulupa crop production (Passiflora edulis f. edulis

A field experiment was carried out at Krishi Vigyan Kendra, Katihar, Bihar in jurisdiction of Bihar Agricultural University Sabour, Bhagalpur during 2014 to 2018 with the objective to find out suitable crop residue management option under rice- wheat cropping system in Inceptisols of Seemanchal area of Bihar. The results after four years clearly indicates that the crop residue management practices involving  incorporation of residues improved favorably and significantly the soil properties such as bulk density, infiltration rate, mean weight diameter, aggregate stability, electrical conductivity, organic carbon, available nitrogen, phosphorus and potassium, bacterial and fungal population, enzyme dehydrogenase and phosphatase activity in the soil and increased the grain yields of rice and wheat crop in the system over removal or burning of crop residue practices. Due to increased availability of readily decomposable organic matter in the form of crop residue and freshly incorporated green manure, the microbial population increased dramatically when crop residues are incorporated in the soil which might be responsible for increased enzyme phosphatase and dehydrogenase activity, decrease in bulk density, increase in granulation and aggregation and thus infiltration rate. The incorporation of crop residues with or without green manuring found promising for the environmental friendly and effective utilization of the crop residues under prevailing rice wheat system in this area.

A two-compartment mathematical model is proposed for the study of individual plant growth dynamics with time lag due to the presence of toxic metals in the soil. It is assumed in the model that nutrient uptake by the roots is hindered by the presence of the toxic metals. It is further assumed that there is less transfer of nutrients from the root compartment to the shoot compartment due to the toxic metals. However, the nutrient concentration decreases in the root compartment as well as in the shoot compartment, resulting in a decrease of the structural dry weight of the roots and shoots respectively. This effect was studied by considering time lag in the utilization coefficient of the nutrient concentration in the roots in the presence of toxic metals. It is further assumed in the model that the nutrient use efficiency is also affected by the presence of toxic metals, resulting in a decrease of the structural dry weight of the shoots. The inclusion of time lag results in the disturbance of the interior equilibrium stability and Hopf bifurcation occurs for a critical value of the delay parameter. This entire phenomenon was captured by numerical simulation.

Rice (Oryza sativa L.)-wheat (Triticum aestivum L. emend. Fiori and Paol.) is the most important two crops a year intensive rice based cropping system of Asia. Agronomic management is the most important input for getting potential yield and high net returns in any crop or crop sequence. Most of the farmers used to grow old varieties of rice and wheat without any row arrangement. Fertilization is mainly limited to nitrogenous fertilizer only. Therefore, the present study was undertaken to find out the effect of different agronomic management practices on productivity and economics of rice-wheat system at farmers’ fields. Inclusion of improved variety in rice and wheat incurred additional cost of $52/ha and provided additional return of $101/ha, whereas sowing/transplanting of rice and wheat in lines incurred additional cost of $30/ha and resulted in additional returns of $146/ha. Balanced fertilization incurred additional cost of $38 over the imbalanced fertilization and provided additional returns of $180/ha. Recommended package of practices (improved variety, line sowing/transplanting and balanced fertilization) incurred additional cost of cultivation of $120/ha over the farmers’ practice and achieved additional net returns of $426/ha.

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