Rice Rotation System Research Articles

Greenhouse gas emissions and global warming potential of traditional and diversified tropical rice rotation systems.

Global rice agriculture will be increasingly challenged by water scarcity, while at the same time changes in demand (e.g. changes in diets or increasing demand for biofuels) will feed back on agricultural practices. These factors are changing traditional cropping patterns from double-rice cropping to the introduction of upland crops in the dry season. For a comprehensive assessment of greenhouse gas (GHG) balances, we measured methane (CH4 )/nitrous oxide (N2 O) emissions and agronomic parameters over 2.5years in double-rice cropping (R-R) and paddy rice rotations diversified with either maize (R-M) or aerobic rice (R-A) in upland cultivation. Introduction of upland crops in the dry season reduced irrigation water use and CH4 emissions by 66-81% and 95-99%, respectively. Moreover, for practices including upland crops, CH4 emissions in the subsequent wet season with paddy rice were reduced by 54-60%. Although annual N2 O emissions increased two- to threefold in the diversified systems, the strong reduction in CH4 led to a significantly lower (P<0.05) annual GWP (CH4 +N2 O) as compared to the traditional double-rice cropping system. Measurements of soil organic carbon (SOC) contents before and 3years after the introduction of upland crop rotations indicated a SOC loss for the R-M system, while for the other systems SOC stocks were unaffected. This trend for R-M systems needs to be followed as it has significant consequences not only for the GWP balance but also with regard to soil fertility. Economic assessment showed a similar gross profit span for R-M and R-R, while gross profits for R-A were reduced as a consequence of lower productivity. Nevertheless, regarding a future increase in water scarcity, it can be expected that mixed lowland-upland systems will expand in SE Asia as water requirements were cut by more than half in both rotation systems with upland crops.

Biochar use in a legume–rice rotation system: effects on soil fertility and crop performance

The aim of this study was to determine whether by applying biochar, it is possible to augment the beneficial effects of legume–crop rotation systems on soil fertility and crop performance. Repeated experiments were established in 2012 and 2013 in South-western Benin using a split-split plot design. Two legumes, Mucuna pruriens (mucuna) and Vigna unguiculata (cowpea), were planted for 42 days on biochar-amended and unamended plots and subsequently cut and applied as mulch 5 days before planting rice. Rice plants were either fertilized or not using a fertilizer rate of 60, 30, and 30 kg ha−1 of N, P2O5, and K2O, respectively. The results showed that the application of legume green manures and fertilizer, either singly or in combination, improved soil nutrient availability, CEC, shoot yield, and grain yield of rice on both biochar-amended and unamended plots. However, the effect was significantly (p < 0.05) greater on biochar-amended plots. The mean grain yield for all cropping seasons was 1.8 t ha−1 for biochar-amended plots and 1.3 t ha−1 for unamended plots. The greater grain yield of rice on biochar-amended plots was associated with improved soil fertility and increased N uptake.

Studies of the Italian ryegrass–rice rotation system in southern China: Arbuscular mycorrhizal symbiosis affects soil microorganisms and enzyme activities in the Lolium mutiflorum L. rhizosphere

Greater understanding of roles of arbuscular mycorrhizal fungi (AMF) in roots of Italian ryegrass (Lolium mutiflorum L.) is required, particularly in the Italian ryegrass–rice rotation (IRR) system applied in southern China. Therefore, we examined growth of Italian ryegrass inoculated with either or both of two AMF species (Glomus mosseae and G. versiforme), and AMF-free controls, in pots. AMF in the roots promoted ryegrass biomass accumulation and affected both the soil microorganisms and rhizosphere enzyme activities. Inoculation with G. versiforme alone resulted in the highest percentage of mycorrhizal root colonization and highest soil urease activity. Inoculation with either AMF species alone also resulted in much higher ryegrass root dry weights than use of both species (P<0.05), but the reverse was true for soil invertase activity and the abundance of soil fungi and actinomyces. We also explored effects of AMF on N and P uptake by the ryegrass, soil microbes and enzymes in a multi-compartment rhizobox experiment with two treatments: inoculation with viable and autoclaved G. versiforme. Despite a low root colonization percentage, the presence of viable AMF markedly increased: alkaline phosphatase and urease activities in the rhizosphere (P<0.05); the abundance of ammonifying bacteria, nitrosobacteria, denitrifying bacteria and inorganic phosphobacteria; and both N and P uptake of the plants. Root N contents were positively correlated with both soil urease activity and soil denitrifying bacteria (P<0.05), while shoot and root P contents were positively correlated with soil total P and available P, respectively (P<0.05). Thus, AMF colonization clearly increased the abundance of soil microorganisms and enzyme (excluding invertase) activities, thereby enhancing N and P uptake of the ryegrass.

Modeling Impacts of Alternative Practices on Net Global Warming Potential and Greenhouse Gas Intensity from Rice–Wheat Annual Rotation in China

BackgroundEvaluating the net exchange of greenhouse gas (GHG) emissions in conjunction with soil carbon sequestration may give a comprehensive insight on the role of agricultural production in global warming.Materials and MethodsMeasured data of methane (CH4) and nitrous oxide (N2O) were utilized to test the applicability of the Denitrification and Decomposition (DNDC) model to a winter wheat – single rice rotation system in southern China. Six alternative scenarios were simulated against the baseline scenario to evaluate their long-term (45-year) impacts on net global warming potential (GWP) and greenhouse gas intensity (GHGI).Principal ResultsThe simulated cumulative CH4 emissions fell within the statistical deviation ranges of the field data, with the exception of N2O emissions during rice-growing season and both gases from the control treatment. Sensitivity tests showed that both CH4 and N2O emissions were significantly affected by changes in both environmental factors and management practices. Compared with the baseline scenario, the long-term simulation had the following results: (1) high straw return and manure amendment scenarios greatly increased CH4 emissions, while other scenarios had similar CH4 emissions, (2) high inorganic N fertilizer increased N2O emissions while manure amendment and reduced inorganic N fertilizer scenarios decreased N2O emissions, (3) the mean annual soil organic carbon sequestration rates (SOCSR) under manure amendment, high straw return, and no-tillage scenarios averaged 0.20 t C ha−1 yr−1, being greater than other scenarios, and (4) the reduced inorganic N fertilizer scenario produced the least N loss from the system, while all the scenarios produced comparable grain yields.ConclusionsIn terms of net GWP and GHGI for the comprehensive assessment of climate change and crop production, reduced inorganic N fertilizer scenario followed by no-tillage scenario would be advocated for this specified cropping system.

Agronomic and physiological performance of high-yielding wheat and rice in the lower reaches of Yangtze River of China

Understanding agronomic and physiological performance of crop high yield is essential to make strategies for breeding and crop management. This study aimed to identify major agronomic and physiological traits associated with high grain yields of rice and wheat in the wheat–rice rotation system in the lower reaches of Yangtze River of China. Two high-yielding cultivars, each for winter wheat and rice, were field-grown from 2008 to 2010 for 3 years. Two crop management treatments, the local farmer's practice (LFP) and improved high-yielding cultivation (IHC), were used. The IHC adopted two new techniques, i.e., site-specific nitrogen management in both rice and wheat and alternate wetting and moderate drying irrigation in rice and controlled soil drying irrigation in wheat. Across the 3 years, the IHC yielded an average 9.67tha−1 of wheat and 12.55tha−1 of rice with an annual total of 22.2tha−1, an increase of 26.8% when compared with that (17.5tha−1) under the LFP. The increased grain yield under the IHC was mainly attributed to expanded sink size as a result of more kernels per spike or more spikelets per panicle, increased kernel weight of wheat and increased percentage of filled grains of rice. When compared with LFP, IHC showed a greater percentage of productive tillers, more pre-anthesis nonstructural carbohydrate (NSC) storage in the stem, greater leaf photosynthetic rate and concentration of cytokinins in root exudates, higher activities of sucrose synthase and adenosine diphosphoglucose pyrophosphorylase in grains, more dry mater production during the grain filling period, and higher harvest index. We conclude that (1) expanding sink capacity through an increase in kernels per spike or spikelets per panicle, (2) enhancing grain filling efficiency by an increase in pre-anthesis NSC in the stem, and (3) increasing post-anthesis dry mater production by an enhancement in root activity during grain filling should be considered as three major strategies for further increases in grain yields of wheat and rice in the lower reaches of Yangtze River of China.

Influence of Rice Rotation Systems on Soil Nematode Trophic Groups in Arkansas

The effects of crop rotation sequences and combinations on soil nematode populations were investigated. Tillage versus non-tillage treatments were applied to crop rotation sequences dominated by flooded rice in a split plot design. The rotated crops were rice, soybean, and corn, including a fallow for a total of eight rotation treatments. All nematode feeding groups were recovered i.e bacterial feeding-, fungal feeding-, plant feeding-, carnivorous-, and omnivorous- nematodes. A total of 24 nematode genera in 20 families were identified and categorized into their respective trophic groups and colonizer persister (cp) values. All rotations that included soybean significantly (P<0.05) or numerically increased soil nematode populations, irrespective of trophic groups, while all rotations that included rice and corn, had a nematode reductive effect. No-tillage plots recorded significantly higher populations of the predatory nematodes. The effectiveness of a rotation sequence depends primarily on the crop species and secondarily on soil conditions e.g anaerobic.

Short-term effects of conservation management practices on soil labile organic carbon fractions under a rape–rice rotation in central China

Conservation management practices, such as no-tillage (NT) or crop residue mulch, alter soil organic carbon (C) lability, thus affecting soil quality. However, inconsistent effects of conservation management practices on soil labile organic C have been commonly reported. We hypothesized, however, that conservation management practices can improve soil labile organic C fractions and then C management index (CMI) and soil quality. Thus, our objective was to quantify labile organic C contents on a clay loam soil (Anthrosols, World Reference Base for Soil Resources) 3 years after implementing four tillage/crop residue management treatments under a rice Liangyoupeijiu (Oryza sativa L.)–rape Huayouzaliuhao (Brassica napus) rotation in Wuxue City of central China. The experiment included four treatments: (1) single conventional tillage (CT) without crop residue (rape with NT–rice with CT); (2) double CT without crop residue (rape with CT–rice with CT); (3) double NT without crop residue (rape with NT–rice with NT); and (4) double NT plus crop residue (rape with NT+rice residue mulch–rice with NT+rape residue mulch). Five soil organic C fractions were determined from 0 to 30cm layer in October 2009 (3 years after a rape–rice double crop rotation). Total organic C, microbial biomass C, dissolved organic C, particulate organic C, easily oxidizable C, and water stable aggregation were measured. A CMI was also calculated. The concentrations of total organic C, microbial organic C, dissolved organic C, and particulate organic C under the double NT plus crop residue treatment were 1.07–1.17, 1.20–1.26, 1.08–1.30 and 1.17–1.76 times higher than those under the other three treatments. The total organic C and labile organic C contents under the double NT with or without crop residue treatment were generally higher at 0–5cm than at greater sampling depths. The proportions of 0.5–2mm water-stable aggregates at the 0–5cm depth under the double NT with or without crop residue treatment were significantly greater (P<0.05) than those under the single or double CT without crop residue treatment, but lower (P<0.05) at the 5–30cm depth. Soil labile organic C fractions were positively correlated with each other. The greater C pool index (CPI) at the 0–5cm depth observed under double NT with or without crop residue treatment compared to single or double CT without crop residue treatment led to greater CMI at the same depth. However, CMI at the 5–30cm depth was lower for the double NT with or without crop residue treatment compared to the single or double CT without crop residue treatment. Thus, our results indicated that soil labile organic C fractions were only sensitive to changes in management practices in the upper soil profile, and that short-term effects of continuous NT or NT with crop residue mulch in a rape–rice rotation system appeared to only improve soil quality in the upper soil profile. Based on these results, we suggested that greater quantities of labile organic C can be concentrated in the 0–30cm soil layer of a soil under rape–rice rotation by more sustainable practices than those currently being used in central China.

Broussonetia papyrifera (paper mulberry): its growth, yield and potential as a fallow crop in slash-and-burn upland rice system of northern Laos

In northern Laos, shortened fallows in the slash-and-burn upland rice system are not sustainable either from a production or economic standpoint. This paper evaluates the potential for using the indigenous fast-growing tree, Broussonetia papyrifera L. Vent. (paper mulberry) as an economic fallow crop. The objectives of this study are to assess the inner bark yield of paper mulberry, and to evaluate rice productivity following paper mulberry cultivation. In addition, allometric models for estimating the inner bark yield of paper mulberry are developed. Inner bark yield of paper mulberry stands ranging in age from 9 to 48 months ranged from 10 to 208 g m−2, and increased with age. The models using diameter at breast height and stem height, or diameter at breast height only as independent variables explained well the variation in inner bark yield. When paper mulberry was completely removed during the rice growing season, rice yields in these areas were similar to those following weedy bush fallow. When paper mulberry was allowed to grow, rice yields were negatively correlated to paper mulberry stem density. When paper mulberry lateral branches were pruned back, rice yields could be maintained if the paper mulberry stem density was <0.22 stems m−2, suggesting that if paper mulberry is managed properly, rice yields can be maintained at current levels. The paper mulberry-upland rice rotation system improves the productivity of a traditional slash-and-burn system through harvesting paper mulberry inner bark; however the long-term sustainability of such a system remains unclear and warrants further investigation.