Integrated effect of population and weed management regimes on weed dynamics,performance, and productivity of basmati rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Weeds caused serious problem on yield reduction of basmati rice worldwide. Losses caused by weeds varied from one country to another, depending on the presence of dominant weeds and the control methods practiced by farmers; therefore, suitable plant population and weed management practices should be adopted. Keeping these in mind, a field experiment was carried out during kharif seasons of 2009 and 2010 at crop Research Centre of SVPUA&T, Meerut, India comprising 4 planting geometries, viz. 20, 30, 40, and 50 hills m^?2 as main plot factor, and 5 weed management practices (Butachlor @ 1.0 kg ha^?1, Butachlor @ 1.0 kg ha^?1 fb (followed by) one hand weeding, Butachlor @ 1.0 kg ha^?1 fb Almix @ 4 g ha^?1, two hand weedings and weedy check) in a split plot design with 3 replications. Experimental results revealed that plant population of 50 hills m^?2 proved superior over that of 20 hills m^?2 in respect of weed density, weed dry weight, number of tillers m^?2, yield attributes, grain, straw, and biological yields. The maximum grain yield (29.00 and 31.00 q ha^?1) and straw yield (51.30 and 52.50 q ha^?1) were recorded in 50 hills m^?2 followed by 40 hills m^?2 during 2009 and 2010, respectively. In respect of nitrogen, phosphorus, and potassium removal, a reverse trend was observed: the highest in 20 hills m^?2 followed by 30, 40, and 50 hills m^?2. As far as the weed management practices are concerned, both chemical and mechanical methods of weed control were found superior over weedy check. The lowest weed density, dry weight, and highest weed control efficiency, maximum length of panicle^?1, number of panicle (m²), and 1000-grain weight and grain yield of 30.40 and 32.60 q ha^?1 were recorded with two hand weedings which was at par with Butachlor @ 1.0 kg ha^?1 fb one hand weeding over rest of the weed management practices.     

Distribution,habitat associations and conservation implications of Sri Lankan freshwater terrapins outside the protected area network

1. Terrapins are integral to many freshwater ecosystems, yet are imperilled at a global scale. In Sri Lanka, terrapins are understudied; thus, much of their natural history and distribution status remain unknown. Such paucity of studies impedes conservation.
2. In this study, 79 freshwater habitats located outside the protected area network of south‐western Sri Lanka were surveyed to document current population densities and habitat use of two terrapin species: Indian black terrapin (Melanochelys trijuga thermalis ) and flap‐shelled terrapin (Lissemys ceylonensis ). Local inhabitants were interviewed to assess human threats towards terrapins.
3. Both species were recorded in low densities: 1–2 individuals ha^?1. Indian black terrapin was found in half of the surveyed sites while flap‐shelled terrapin occurred in one‐third of the surveyed sites. Highly urbanized river basins had the lowest densities for both species while rural basins supported higher numbers. Basking was the predominant behaviour of both species and large woody debris and boulders were preferred as basking substrates, together with sparse‐canopy aquatic habitats with intact marshlands.
4. Overharvesting for meat was a major threat for terrapins. Most local inhabitants were unaware of legislation on terrapin conservation and the ecological importance of terrapins. Human threats such as pollution, modification of aquatic and wetland habitats, and loss of riparian forests were frequently observed in surveyed sites. Terrapin populations outside the protected area are at risk as evidenced by lower population densities and a multitude of human threats.
5. A landscape‐scale ecosystem‐based conservation approach is recommended for Sri Lanka's terrapins with incorporation of lands with different management regimes (privately owned, municipality managed) into the protected area network. Current environmental legislation should be revised to support buffer zone delineation for aquatic habitats, wetland restoration, and landscape‐scale connectivity.

     

Characterization and antimicrobial susceptibility of biofilm-producing Avian Pathogenic Escherichia coli from broiler chickens and their environment in India

Veterinary Research Communications - Avian pathogenic Escherichia coli (APEC) is responsible for colibacillosis in poultry. APEC remains a constant problem for the poultry industry, despite the use...     

Influence of chloride and sulphate ions on soil enzymes

Ammonium chloride (AC) and ammonium sulphate (AS) are commonly used nitrogen fertilizers. But the effect of chloride and sulphate ions from these fertilizers on soil enzyme activity has received scant attention. Hence, we conducted a pot culture study to assess the influence of chloride (as AC) and sulphate (as AS) on the activities of urease, amidase, phosphatase and dehydrogenase in soil using rice as the test crop. Chloride and sulphate levels were fixed at 132, 264 and 396 kg ha⁻¹ respectively. Controls were also performed. The enzymes were assayed at three stages of the crop growth viz., active tillering, panicle initiation and harvest.
The enzyme activities decreased with increasing chloride and sulphate levels; however, the degree of inhibition varied among the enzymes assayed and the nature and amounts of salts added. The inhibition may be due to the specific effects of chloride and sulphate ions on microbial growth and subsequent enzyme synthesis, osmotic desiccation leading to microbial cell lysis, and a salting-out effect modifying the ionic conformation of the active site of the enzyme protein.     

Identification and marker‐assisted introgression of QTL conferring resistance to bacterial leaf blight in cowpea (Vigna unguiculata (L.) Walp.)

Bacterial leaf blight (BLB), caused by Xanthomonas axonopodis pv. vignicola (Xav), is widespread in major cowpea [Vigna unguiculata (L.) Walp.] growing regions of the world. Considering the resource poor nature of cowpea farmers, development and introduction of cultivars resistant to the disease is the best option. Identification of DNA markers and marker‐assisted selection will increase precision of breeding for resistance to diseases like bacterial leaf blight. Hence, an attempt was made to detect QTL for resistance to BLB using 194 F_2 : 3 progeny derived from the cross ‘C‐152’ (susceptible parent) × ‘V‐16’ (resistant parent). These progeny were screened for resistance to bacterial blight by the leaf inoculation method. Platykurtic distribution of per cent disease index scores indicated quantitative inheritance of resistance to bacterial leaf blight. A genetic map with 96 markers (79 SSR and 17 CISP) constructed from the 194 F₂ individuals was used to perform QTL analysis. Out of three major QTL identified, one was on LG 8 (qtlblb‐1) and two on LG 11 (qtlblb‐2 and qtlblb‐3). The PCR product generated by the primer VuMt337 encoded for RIN2‐like mRNA that positively regulate RPM1‐ and RPS2‐dependent hypersensitive response. The QTL qtlblb‐1 explained 30.58% phenotypic variation followed by qtlblb‐2 and qtlblb‐3 with 10.77% and 10.63%, respectively. The major QTL region on LG 8 was introgressed from cultivar V‐16 into the bacterial leaf blight susceptible variety C‐152 through marker‐assisted backcrossing (MABC).     

Manure and Fertilizer Application Effects on Aggregate and Mineral-Associated Organic Carbon in a Loamy Soil under Rice-Wheat System

The study was conducted to investigate the aggregate stability and distribution of organic carbon (C) in different-sized aggregates and mineral fractions in a loamy soil under rice-wheat system with continuous application of fertilizer nitrogen, phosphorus and potassium (NPK), farmyard manure (FYM), N+FYM and NPK+FYM, compared with unfertilized control. Macro-aggregates comprised 37.1–49.3% of the total water-stable aggregates (WSAs), compared with 23.3–30.3% as micro-aggregates. Application of inorganic fertilizers and FYM significantly increased the proportion of macro-aggregates, which were linearly related to total organic C (TOC). Organic C concentration in coarse macro-aggregates (CMacA) was higher than the micro-aggregates (CMicA). Application of FYM significantly increased the concentration of organic C in different-sized aggregates and mineral fraction, compared with the unfertilized control. Averaged across treatments, mineral-associated C comprised 26% of TOC. Macro-aggregates, on an average, constituted 66–68% of C preservation capacity of WSA. The amount of TOC sequestered was higher when NPK+FYM was applied together.     

Agronomic evaluation of mulching and iron nutrition on productivity,nutrient uptake,iron use efficiency and economics of aerobic rice-wheat cropping system

Field experiments were carried out during rainy (kharif) and winter (rabi) seasons (June–April) of 2008–2010 at Indian Agricultural Research Institute (IARI), New Delhi, to study the productivity, nutrients uptake, iron (Fe) use-efficiency and economics of aerobic rice-wheat cropping system as influenced by mulching and Fe nutrition. The highest yield attributes, grain and straw yields (5.41 tonnes ha^?1 and 6.56 tonnes ha^?1, respectively) and nutrient uptake in rice was recorded with transplanted and puddled rice (TPR) followed by aerobic rice with Sesbania aculeata mulch. However, residual effect of aerobic rice with wheat straw mulch was more pronounced on yield attributes, grain and straw yields (4.20 and 6.70 tonnes ha^?1, respectively) and nutrient uptake in succeeding wheat and remained at par with aerobic rice with Sesbania mulch. Application of iron sulfate (FeSO₄) at 50 kg ha^?1 + 2 foliar sprays of 2% FeSO₄ was found to be the best in terms of all the yield attributes, grain and straw yield (5.09 and 6.17 tonnes ha^?1, respectively) and nutrient uptake and remained at par with 3 foliar sprays of 2% FeSO₄. Although residual effect of iron application failed to increase the yield attributes, yield and nutrient uptake nitrogen, phosphorus and potassium (N, P, K) except Fe. The highest system productivity, nutrient uptake, gross returns, net returns, B: C ratio and lowest cost of cultivation were recorded with aerobic rice with wheat straw and Sesbania aculeata mulch. Application of FeSO₄ at 50 kg ha^?1 + two foliar sprays of 2% FeSO₄ was found better in respect of system productivity, nutrient uptake, gross returns, net returns, B:C ratio and cost of cultivation in aerobic rice-wheat cropping system. The Fe use efficiency values viz. partial factor productivity (kg grain kg^?1 Fe), agronomic efficiency (kg grain increased kg^?1 Fe applied), agrophysiological efficiency (kg grain kg^?1 Fe uptake), physiological efficiency (kg biomass kg^?1 Fe uptake), apparent recovery (%) utilization efficiency and harvest index (%) of applied Fe were significantly affected due to methods of rice production and various Fe nutrition treatments in aerobic rice and aerobic rice-wheat cropping system.