Organic Matter and Mineralizable Nitrogen Relationships in Wetland Rice Soils

Abstract

Soil nitrogen (N) supply plays a dominant role in the N nutrition of wetland rice. Organic matter has been proposed as an index of soil N availability to wetland rice. This is based on the finding that mineralizable N produced under waterlogged conditions is related to soil organic carbon (C) and total N. The relationship between organic matter and mineralizable N is a prerequisite for determining the N requirement of wetland rice. However, no critical analysis of recent literature on organic mattermineralizable N relationships has been made. This article evaluates current literature on the relationships of mineralizable N or ammonium N production with soil organic C in wetland rice soils. A number of studies with diverse wetland rice soils demonstrate a close relationship of N mineralized (ammonium-N) under anaerobic conditions with organic C or total N. However, a few recent studies made on sites under long-term intensive wetland rice cropping showed that strong positive relationships of mineralizable N with organic C or total N do not hold. Clearly, both quantity and quality of organic matter affect N mineralization in wetland rice soils. Future research is needed to clarify the role of quality of organic matter, especially its chemistry, as modified by the chemical environment of submerged soils, on the mineralization of organic N in wetland rice soils.

Effect of Nitrogen Rates and Split Nitrogen Fertilization on Grain Yield and its Components in Flooded Rice

“…For fertilization, N is the main nutrient associated with yield (Angus et al, 1994;Wilson et al, 1994a;Sahrawat, 2006;Bouman et al, 2007;De-Xi et al, 2007;Jing et al, 2008). Its availability promotes crop growth and tillering, finally determining the number of panicles and spikelets during the early panicle formation stage.…”

Impact of nitrification inhibitor with organic manure and urea on nitrogen dynamics and N2O emission in acid sulphate soil

“…Fertilizer N management practices have a cumulative effect on N cycling and availability over time. Mineralized N or NH 4 + released under anaerobic incubation are significantly correlated with soil organic matter; however, both quality and quantity of organic matter clearly affect N-mineralization in wetland rice soils (Sahrawat 2006). The greater part of N in paddy soil exists in soil organic matter.…”

Relationship between mineralized nitrogen during anaerobic incubations and residual effect of nitrogen fertilization in two rice paddy soils in Chil

“…Mean mineralized N-NH4 + concentration in the Vertisol was 54.15 mg kg -1 at 160 kg N ha -1 rate applied in the previous season for 21 d incubation (Figure 1b). The differences in the amount of mineralized N in both soils respond to higher N uptake of the previous season in Vertisol (Hirzel and Rodríguez, 2013) and to the dynamics of N-NH4 + adsorption and desorption in the dominant type of clay (Montmorillonite) in the Vertisol under incubation conditions (Nieder et al, 2010), which in turn is mediated by soil biomass (Jensen et al, 2000;Sainz et al, 2004;Sahrawat, 2006) as well as the degree of K saturation (Table 1) in the intermediate layers of clay minerals (Nieder et al, 2010). The submerged condition of rice paddy soils is also a factor that influences the level of soil N-NH4 + mineralization; however, it can lead to contradictory conclusions about the extent of mineralization.…”

“…Mineralized N was correlated with crop N uptake through different combinations of temperature and time (Srpska and Sad, 2005;Yan et al, 2006), and the correlation values allowed determination of the most appropriate method (incubation time and temperature) for each soil; to this end, a linear mathematical model in the SAS simple regression function (Wilson et al, 1994;Sahrawat, 2006;Hirzel et al, 2012) and ANOVA were used. To determine the ratio index (Uptake Index) between crop N uptake from the residual effect of N fertilization and N mineralization in each type of soil (Sørensen and Amato, 2002), the following equation was used:…”

“…Moreover, since N absorbed by the plant is mainly from reserves generated by organic matter mineralization, microbial biomass activity, fixed N-NH4 + in clay (Sainz et al, 2004;Sahrawat, 2006), and fertilization (Wienhold, 2007). However, accurate prediction of N mineralization is difficult due to intercrossing effects of the variables involved in crop management, such as climatic conditions and soil type (Li et al, 2001;Fan et al, 2005a).…”