Linking spatio-temporal variation of crop response with sediment deposition along paddy rice terraces

Abstract In tropical mountainous regions of South East Asia, intensive cultivation of annual crops on steep slopes makes the area prone to erosion resulting in decreasing soil fertility. Sediment deposition in the valleys, however, can enhance soil fertility, depending on the quality of the sediments, and influence crop productivity. The aim of the study was to assess (i) the spatio-temporal variation in grain yield along two rice terrace cascades in the uplands of northern Viet Nam, (ii) possible linkage of sediment deposition with the observed variation in grain yield, and (iii) whether spatial variation in soil water or nitrogen availability influenced the obtained yields masking the effect of inherent soil fertility using carbon isotope ( 13 C) discrimination and 15 N natural abundance techniques. In order to evaluate the impact of seasonal conditions, fertilizer use and sediment quality on rice performance, 15 N and 13 C stable isotope compositions of rice leaves and grains taken after harvest were examined and combined with soil fertility information and rice performance using multivariate statistics. The observed grain yields for the non-fertilized fields, averaged over both cascades, accounted for 4.0 ± 1.4 Mg ha −1 and 6.6 ± 2.5 Mg ha −1 in the spring and summer crop, respectively, while for the fertilized fields, grain yields of 6.5 ± 2.1 Mg ha −1 and 6.9 ± 2.1 Mg ha −1 were obtained. In general, the spatial variation of rice grain yield was strongly and significantly linked to sediment induced soil fertility and textural changes, such as soil organic carbon ( r 0.34/0.77 for Cascades 1 and 2, respectively) and sand fraction ( r −0.88/−0.34). However, the observed seasonal alteration in topsoil quality, due to sediment deposition over two cropping cycles, was not sufficient to fully account for spatial variability in rice productivity. Spatial variability in soil water availability, assessed through 13 C discrimination, was mainly present in the spring crop and was linearly related to the distance from the irrigation channel, and overshadowed in Cascade 2 the expected yield trends based on sediment deposition. Although δ 15 N signatures in plants indicated sufficient N uptake, grain yields were not found to be always significantly influenced by fertilizer application. These results showed the importance of integrating sediment enrichment in paddy fields within soil fertility analysis. Furthermore, where the effect of inherent soil fertility on rice productivity is masked by soil water or nitrogen availability, the use of 13 C and 15 N stable isotopes and its integration with conventional techniques showed potential to enhance the understanding of the influence of erosion – sedimentation and nutrient fluxes on crop productivity, at toposequence level.

[1]  P. N. Hinz,et al.  Interpreting Within-Field Relationships Between Crop Yields and Soil and Plant Variables Using Factor Analysis , 2004, Precision Agriculture.

[2]  J. Ladha,et al.  Nitrogen accumulation and changes in natural 15N abundance in the tissues of legumes with emphasis on N2 fixation by stem-nodulating plants in upland and paddy fields , 1991 .

[3]  M. Sheshshayee,et al.  Carbon Isotope Discrimination Accurately Reflects Variability in WUE Measured at a Whole Plant Level in Rice , 2005 .

[4]  K. Bandyopadhyay,et al.  Nitrogen Use Efficiency, 15N Balance, and Nitrogen Losses in Flooded Rice in an Inceptisol , 2005 .

[5]  Ronald P. Cody,et al.  Applied Statistics and the SAS Programming Language , 1986 .

[6]  Bas A. M. Bouman,et al.  The effect of toposequence position on soil properties, hydrology, and yield of rainfed lowland rice in Southeast Asia , 2008 .

[7]  J. Ehleringer,et al.  Carbon Isotope Discrimination and Photosynthesis , 1989 .

[8]  J. Diels,et al.  Differential 13C Isotopic Discrimination in Maize at Varying Water Stress and at Low to High Nitrogen Availability , 2006, Plant and Soil.

[9]  J. Six,et al.  Considerations of a field-scale soil carbon budget for furrow irrigation , 2006 .

[10]  J. Six,et al.  Annual carbon and nitrogen loadings for a furrow-irrigated field , 2009 .

[11]  Ying-xin Xie,et al.  Nitrogen fate and environmental consequence in paddy soil under rice-wheat rotation in the Taihu lake region, China , 2009, Plant and Soil.

[12]  R. Nagarajan,et al.  Soil Fertility and Indigenous Nutrient Supply in Irrigated Rice Domains of Asia , 2003 .

[13]  N. Kato,et al.  Changes in natural 15N abundance in paddy soils under different, long-term soil management regimes in the Tohoku region of Japan , 2007 .

[14]  F. Nachtergaele,et al.  World Reference Base for Soil Resources. Introduction , 1998 .

[15]  J. Raven,et al.  The use of natural abundance of nitrogen isotopes in plant physiology and ecology , 1992 .

[16]  A. Mochizuki,et al.  Increased productivity of rainfed lowland rice by incorporation of pond sediments in Northeast Thailand , 2006 .

[17]  Mitsuru Tsubo,et al.  Toposequential effects on water balance and productivity in rainfed lowland rice ecosystem in Southern Laos , 2006 .

[18]  T. Hilger,et al.  13C isotopic discrimination: a starting point for new insights in competition for nitrogen and water under contour hedgerow systems in tropical mountainous regions , 2007, Plant and Soil.

[19]  Georg Cadisch,et al.  Sediment induced soil spatial variation in paddy fields of Northwest Vietnam , 2010 .

[20]  K. Homma,et al.  Toposequential Variation in Soil Fertility and Rice Productivity of Rainfed Lowland Paddy Fields in Mini-Watershed (Nong)in Northeast Thailand , 2003 .

[21]  G. Billen,et al.  Nitrogen isotopic composition of leached nitrate and soil organic matter as an indicator of denitrification in a sloping drained agricultural plot and adjacent uncultivated riparian buffer strips , 2010 .

[22]  L. Schrader,et al.  Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid , 1975 .

[23]  Duning Xiao,et al.  Spatial variability of soil properties in relation to land use and topography in a typical small watershed of the black soil region, northeastern China , 2008 .

[24]  J. Deckers,et al.  World Reference Base for Soil Resources , 1998 .

[25]  J. Raven,et al.  Influences of different nitrogen sources on nitrogen- and water-use efficiency, and carbon isotope discrimination, in C3Triticum aestivum L. and C4Zea mays L. plants , 1998, Planta.

[26]  S. Haefele,et al.  Nutrient management for rainfed lowland rice in northeast Thailand , 2009 .

[27]  D. Long,et al.  Nitrogen and Water Stress Interact to Influence Carbon‐13 Discrimination in Wheat , 2001 .

[28]  J. Zhu,et al.  Spatial patterns and effects of soil organic carbon on grain productivity assessment in China , 2008 .

[29]  T. Yoneyama,et al.  Variation of natural 15N abundance of crops and soils in Japan with special reference to the effect of soil conditions and Fertilizer application , 1990 .

[30]  T. Yoneyama,et al.  δ15N Values of sorghum grains harvested on a vertisol in the semi-arid tropics were positively related to doses of fertilizer N but negatively with the frequency of legume cultivation , 2001 .

[31]  B. Lennartz,et al.  Spatial Variability of Soil Properties and Rice Yield Along Two Catenas in Southeast China , 2008 .

[32]  G. Cadisch,et al.  Mixing groundnut residues and rice straw to improve rice yield and N use efficiency , 2009 .

[33]  A. Ghoneim,et al.  Recovery of 15N Derived from Rice Residues and Inorganic Fertilizers Incorporated in Soil Cultivated with Japanese and Egyptian Rice Cultivars , 2008 .

[34]  Randall J. Bernot,et al.  Nutrient cycling relative to δ15N and δ13C natural abundance in a coastal wetland with long-term nutrient additions , 2009, Aquatic Ecology.

[35]  K. Kyuma.  Paddy soil science , 2004 .

[36]  H. Keulen,et al.  Quantitative description of soil organic matter dynamics—A review of approaches with reference to rice-based cropping systems , 2006 .