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The promotion of organic farming involves curtailing extensive use of mineral fertilizers. The present study was aimed to compare the effects of vermicompost (10 Mg ha -1 ), commercial mineral fertilizer (NPK-100:80:80), and their combination on (1) the growth of a major cash crop "onion" (Allium cepa L.) and (2) the changes that may have occurred in the amended soil. The experiment was a randomized complete block design with four replications during the crop-growing season of 2008/09. Results showed significantly higher plant growth in the combined/mix treatment of vermicompost and NPK, as measured by the vegetative growth of bulbs, number and length of tillers per bulb, and fresh weight of bulbs and by the biochemical characteristics of the onion tillers/leaves (total chlorophyll, caretenoids, protein, and total sugar contents). Comparison of the mixed treatment as compared to the control showed increases in bulb size (54%), total number of bulbs per bed (52%), and fresh weight of all bulbs (198%). The chemical properties and enzyme activity of the amended soil also improved significantly in the combined treatment as compared to the application of vermicompost or the mineral fertilizer alone. Total organic C, microbial biomass C, and sulfate content were significantly higher in the mix treatment, with increases of 60%, 127%, and 126%, respectively, as compared to those of the chemical-fertilizer-alone treatment. Similarly, b-glucosidase, alkaline phosphatase, and dehydrogenase were significantly higher by 145%, 91%, 71%, respectively, in the mix treatment as compared to those of fertilizer-alone application. This study indicates that application of a combination of mineral fertilizer and vermicompost in the field can positively influence the biological properties and fertility of soils, and support better plant growth, when compared to the application of mineral fertilizer or vermicompost alone. The study suggests that this combined application can reduce the quantity and cost of mineral-fertilizers application for bulbous-crop cultivation by 50%, while also sustaining soil biological activity of tropical and subtropical soils.

The AP2 domain class of transcription factors is a large family of genes with various roles in plant development and adaptation but with very little functional information in plants other than Arabidopsis. Here, the characterization of an EAR motif-containing transcription factor, SlERF36, from tomato that affects stomatal density, conductance, and photosynthesis is described. Heterologous expression of SlERF36 under the CaMV35S promoter in tobacco leads to a 25–35% reduction in stomatal density but without any effect on stomatal size or sensitivity. Reduction in stomatal density leads to a marked reduction in stomatal conductance (42–56%) as well as transpiration and is associated with reduced CO2 assimilation rates, reduction in growth, early flowering, and senescence. A prominent adaptive response of SlERF36 overexpressors is development of constitutively high non-photochemical quenching (NPQ) that might function as a protective measure to prevent damage from high excitation pressure. The high NPQ leads to markedly reduced light utilization and low electron transport rates even at low light intensities. Taken together, these data suggest that SlERF36 exerts a negative control over stomatal density and modulates photosynthesis and plant development through its direct or indirect effects.

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