Studies on the anaerobic decomposition of plant materials: The anaerobic decomposition of rice straw (Oryza sativa)

An assessment of irrigated rice production energy efficiency and environmental footprint with in-field and off-field rice straw management practices

The research provided scientific evidences for improved rice straw management. Rice cultivation with in-field burning of rice straw is the worst option with the lowest energy efficiency and highest air pollution emission. This article comprises a comparative assessment of energy efficiency and the environmental footprint of rice production using four different rice straw management scenarios, namely, straw retained, straw burned, partial straw removal, and complete straw removal. Paddy yield, grain quality, and energy balance were assessed for two seasons while greenhouse gas emissions (GHGE) were measured weekly starting from land preparation through to the cropping and fallow period. Despite the added energy requirements in straw collection and transport, the use of collected rice straw for mushroom production can increase the net energy obtained from rice production systems by 10-15% compared to burning straw in the field. Partial and complete removal of rice straw reduces GHGE by 30% and 40% compared to complete straw retention, respectively.

Life in a Near-Future Atmosphere: Carbon Dioxide Enrichment Increases Plant Growth and Alters the Behavior of a Terrestrial Snail but not a Terrestrial Beetle

Abstract In addition to effects on climate and water acidification, anthropogenic atmospheric releases of carbon dioxide may also directly impact terrestrial organisms that use CO2 as a chemical cue. We wondered how common organisms would respond to near-future levels of CO2 – levels that may occur by 2025. We chose two common but taxonomically and ecologically dissimilar organisms (Theba pisana helicid snails and Adesmia dilatata tenebrionid beetles) to examine the behavioral effects of a slight rise (~10 ppm) of CO2 on animal abundance and plant growth in the Negev Desert of Israel. We found that plots with supplementary CO2 exhibited greater plant growth than control plots over a 50-day experiment, but increased growth did not alter beetle or snail numbers.

In laboratory experiments with higher levels of augmented CO2 paired with food rewards, we found that snails did not change their climbing behavior when presented with CO2 alone, but they avoided food and climbed away when CO2 was paired with food. Beetles in the laboratory were attracted to food regardless of CO2 levels although high levels of CO2 (1200–1300 ppm) reduced movement.

The direct effects of near-future CO2 levels may augment plant growth but have only minor influence on terrestrial snails and beetles. However, the effects of CO2 on climate change in desert habitats like the Negev may be more severe due to a predicted rise in temperature and a decline in precipitation.

Methane production and oxidation in an anoxic rice soil as influenced by inorganic redox species

The effects of addition of inorganic redox substances (species of NO3-, Mn4+, Fe3+, and SO4(2-)) on methane production and oxidation in anoxic rice (Oryza sativa L.) soil samples were examined. Sulfate was the most inhibitory for methane production followed by Fe3+, NO3-, and Mn4+, in that order. Addition of rice straw at a rate of 1% (w/w) as a carbon source to increase the electron donor to the electron acceptor ratio did not completely alleviate the inhibitory effects of redox species on methane production. Interestingly, laboratory incubation studies showed that addition of MnO2 and K2SO4 enhanced aerobic methane oxidation in soil samples held at 60% water holding capacity. The suspensions of pretreated soil samples with different redox species, when tested for their ability to oxidize methane in soil solution equivalent medium supplemented with respective redox species under aerobic and anaerobic conditions showed differential effects of redox species. Nitrate and Fe3+ stimulated methane oxidation under anaerobic conditions and retarded it under aerobic conditions. Manganese(IV) ion retarded methane oxidation under anaerobic conditions, but enhanced it under aerobic conditions. However, SO4(2-) stimulated methane oxidation in soil solution equivalent medium under both aerobic and anaerobic conditions.