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The effects of rice husk biochar (BC) and coal fly ash (FA) on growth and yield of rice and soil properties were investigated in a lowland rice soil. All growth parameters and yield were positively influenced by the integrated application of BC, FA and chemical fertilisers compared with sole application of chemical fertilisers. Yield increase was 16.4% when BC+FA was applied together with 50% of the recommended dose of nitrogen (N) compared with the recommended dose of N, phosphorus and potassium (NPK). Post-harvest soil analysis suggested that BC and FA both act as a supplier, as well as a reservoir of nutrients. Accumulation of heavy metals in soil and plant parts after harvest was below the toxicity threshold for plants and humans. There was also no significant change in microbial population compared with the initial soil. Therefore, combined application of BC and FA supplemented with chemical fertilisers could be recommended to improve soil fertility and crop productivity without affecting the soil quality. Additional keywords: fertilisers, heavy metals, microbes, nutrients, rice husk. Received 12 October 2015, accepted 20 November 2015, published online 3 June 2016, Introduction Utilisation of agricultural and industrial wastes is a worldwide concern. Among the different agro-wastes, 116 million tonnes of rice husk is produced annually by more than 75 countries (FAO [...]

Flooding imposes severe selection pressure on plants, principally because excess water in their surroundings deprives the plants from certain basic resources such as oxygen, carbon dioxide and light for photosynthesis. Here, the effects of nitrogen and phosphorus application and their application time, on four Indica rice cultivars and their tolerance to submergence under turbid and clear flood water was studied. Submergence tolerance on metabolic changes, photosynthetic (Pn) rate and ethylene accumulation were evaluated. Submergence substantially reduced survival, chlorophyll, soluble sugars, Pn rate across cultivars with drastic reduction in IR-20. Sub1 cultivars showed greater Pn rate as compared to sensitive cultivar under submergence because of better protection of chlorophyll, more stomatal conductance leading to higher survival. Turbid water resulted in lower under-water photosynthesis because of poor light transmission, chlorophyll retention and silt deposition and ultimately poor survival. Foliar spray of N after desubmergence along with basal P improved the chlorophyll, soluble sugars and Pn rate and extenuated ethylene accumulation and shoot elongation resulting in significantly higher survival. To the best of our knowledge, this is the first time that such a study has been performed. Crop establishment could therefore be enhanced in areas where untimely flooding is anticipated by applying basal P and foliar spray of post-submergence N. [ABSTRACT FROM AUTHOR]

Abstract: A field experiment was carried out to investigate the impact of elevated carbon dioxide (CO2) (CEC, 550μmolmol−1) and elevated CO2 +elevated air temperature (CECT, 550μmolmol−1 and 2°C more than control chamber (CC)) on soil labile carbon (C) and nitrogen (N) pools, microbial populations and enzymatic activities in relation to emissions of methane (CH4) and nitrous oxide (N2O) in a flooded alluvial soil planted with rice cv. Naveen in open top chambers (OTCs). The labile soil C pools, namely microbial biomass C, readily mineralizable C, water soluble carbohydrate C and potassium permanganate oxidizable C were increased by 27, 23, 38 and 37% respectively under CEC than CC (ambient CO2, 394μmolmol−1). The total organic carbon (TOC) in root exudates was 28.9% higher under CEC than CC. The labile N fractions were also increased significantly (29%) in CEC than CC. Methanogens and denitrifier populations in rhizosphere were higher under CEC and CECT. As a result, CH4 and N2O-N emissions were enhanced by 26 and 24.6% respectively, under CEC in comparison to open field (UC, ambient CO2, 394μmolmol−1) on seasonal basis. The global warming potential (GWP) was increased by 25% under CEC than CC. However, emissions per unit of grain yield under elevated CO2 and temperature were similar to those observed at ambient CO2. The stimulatory effect on CH4 and N2O emissions under CEC was linked with the increased amount of soil labile C, C rich root exudates, lowered Eh, higher Fe+2 concentration and increased activities of methanogens and extracellular enzymes. [Copyright &y& Elsevier]