Wetland rice

Controlling methane release from wetland, rice paddies and gaseous emissions from animals is more problematic. The release from rice paddies and wet lands is slow, intermittent and takes place over a wide geographic area, and thus very difficult to control. Gaseous emissions from agricultural animals contribute to atmospheric accumulation of methane due to fermentative digestion that produces methane in... 

Conrad R. Control of microbial methane production in wetland rice fields. Nutr. Cycl. Agroecosys. 2002 64 59-69. 

Denier van der Gon HAC, van Breemen N, Neue HU, Lantin RS, Aduna JB, Alberto MCR, Wassmann R. 1996. Release of entrapped methane from wetland rice fields upon soil drying. Global Biogeochem. Cycl. 1996 10 1-7. 

Murthy A.S.P., Zinc fractions in wetland rice soils and their availability to rice. Soil Sci 1982 133 150-154. 

In data assembled by Greenland (1997), the mean level of organic carbon in the topsoils of wetland rice soils from across tropical Asia was 2%, and after excluding acid peaty soils the mean was 1 %. This compares with a range of 1.27-1.81 % for Oxisols and Ultisols of the Cerrado region of Brazil (Sanchez,... 

Figure 4.14 Changes in labile soil P (extractable with HCOs -form anion exchange resin) during 3 years of wetland rice cropping as affected by timing of tillage (early, late = start, end of fallow), incorporation of previous crop s straw, and application of P (20kgha in NPK plots). The overall P balances over 3 years were +37 and +7kgPha in the NPK plots with and without straw, and —90 and — llSkgPha in the PK plots. DS, WS, dry, wet season DAT, days after transplanting (Bucher, 2001). Reproduced by permission...

As we have seen in Section 6.4, wetland rice is particularly efficient at absorbing N03. Kirk and Kronzucker (2000) developed a model to calculate the extent to which rice growing in submerged soil can capture NOs formed in the rhizosphere before it diffuses away and is denitrified in the soil bulk. The model allows for the following processes. 

Deficiency of P is often the main nutrient limitation in natural wetlands, though it is rarely important in wetland rice soils that have at least some history of P... 

The removal of fertilizer N in the crop as NH4+ does not lead to acidification. Hydrolysis of urea fertilizer—by far the main form of N fertilizer used in wetland rice, together with ammonium bicarbonate in some countries—consumes 1 mol of H+ per mol of NH4+ formed (Table 7.1, Process 1). So although absorption of N as NH4+ leads to a net export of H+ from the roots to balance the resulting excess intake of cations over anions (Table 7.1, Process 5), this acidity is matched by the H+ consumed in urea hydrolysis. Likewise there is no net generation of acidity as a result of NH3 volatilization, although 1 mol of H+ is left behind per mol of NH4+ converted to NH3 (Table 7.1, Process 3). 

Bachelet D, Neue HU. 1993. Methane emissions from wetland rice areas of Asia. Chemosphere 26 219-237. 

Conrad R. 1993. Mechanisms controlling methane emission from wetland rice fields. In Oremland R, ed. Biogeochemistry of Global Change. Radiatively Active Gases. New York Chapman HaU, 317-355. 

De Datta SK. 1995. Nitrogen transformations in wetland rice ecosystems. Fertiliser Research 42 193-203. 

Fillery IRP, Simpson JR, De Datta SK. 1986. Contribution of ammonia volatilization to total nitrogen loss after applications of urea to wetland rice fields. Fertiliser Research 8 193-202. 

Ponnamperuma EN. 1985. Chemical kinetics of wetland rice soils relative to soil fertility. In Wetland Soils Characterization, Classification and Utilization. Manila International Rice Research Institute, 71-89. 

Roger PA, Heong KL, Teng PS. 1991. Biodiversity and sustainability of wetland rice production role and potential of microorganisms and invertebrates. In Hawksworth DL, ed. The Biodiversity of Microorganisms and Invertebrates Its Role in Sustainable Agriculture. Wallingford CAB International, 117-136. 

Roger PA, Ladha JK. 1992. Biological N2 fixation in wetland rice fields-estimation and contribution to nitrogen balance. Plant and Soil 141 41-55. 

Natural wetlands Rice paddy fields Enteric fermentation... 

In many areas of the Orient, duck and rice production are linked. Over several generations, native ducks have been selected for their ability to obtain most of their feed requirements from the levees, swamps and waterways associated with wetland rice production. The ducks may also feed on the broken rice left in harvest fields. In some of the rural areas a flock of ducks may be a major source of income. In Indonesia the Alabio and Bali breeds are common while in China the native Maya is used. 

Systematic measurements of CH4 fluxes as well as some time series from wetlands, rice agriculture, landfills, and ruminants were in progress but unpublished at the time of the previous reviews. Reviews by Aselmann and Crutzen (1989), Bartlett and Harriss (1993), Harriss et al. (1993), and Matthews (2000) integrate and summarize a large number of wetland, tundra, and rice smdies and have helped refine our understanding of the... 

Banik S., Sen M., and Sen S. P. (1996) Effects of inorganic fertilizers and micronutrients on methane production from wetland rice Oryza sativa L.). Biol. Fertility Soils 21, 319-322. 

Bogner J. E., Sass R. L., and Walter B. P. (2000) Model comparisons of methane oxidation across a management gradient wetlands, rice production systems, and landfill. Global Biogeochem. Cycles 14, 1021-1033. 

Bouwman A. F. (1991) Agronomic aspects of wetland rice cultivation and associated emissions. Biogeochemistry 15, 65-88. 

Gaunt J. L., Neue H. U., Bragais J., Grant I. F., and Giller K. E. (1997) Soil characteristics that regulate soil reduction and methane production in wetland rice soils. Soil Sci. Soc. Am. J. 61, 1526-1531. 

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