Rice root growth and physiological responses to SRI water management and implications for crop productivity
- 852 Downloads
This paper reports on several research findings on rice root responses, in terms of growth and physiology, manifested when applying System of Rice Intensification water management principles under semi-field and field conditions, in conjunction with variations in plant density and microbial density in the soil. The research aimed to learn about causal relationships, if any, between rice root and shoot growth at different growth stages of the rice plant’s development and their cumulative effect on yield, which is affected by both biotic and abiotic influences. It was seen that greater root length density and a higher rate of root activity affected the yield-contributing parameters in all of the trials, whether conducted under semi-field or field conditions. At the same time, both root parameters were significantly affected by the water regime, soil microbial density, and planting pattern, the three main factors considered. The most important finding observed under semi-field conditions was that enhanced microbial density in the soil improved the sink capacity of the rice plants under all water regimes evaluated. Positive correlations were found between the chlorophyll content of the flag leaf and the duration of grain filling, between the chlorophyll content of plants’ lower leaves and their roots’ oxidizing activity rate, and the roots’ oxidizing activity rate at later growth stage and the available soil nitrogen. These relationships can significantly improve rice plants’ physiological efficiency and hence grain yield, provided that soil nutrients are not a limiting factor and when source–sink demand is maintained simultaneously. To realize the highest crop yield per hectare, both planting pattern and spacing are factors that need to be optimized. This paper in its conclusion considers the relevance of exploiting roots’ potential for plasticity to enhance crop productivity in the context of impending water constraints and climate-change effects.
KeywordsAlternative water regime Root length density Root oxidizing activity rate Root plasticity System of Rice Intensification
The authors would like to thank reviewers for assistances in the improvement of manuscript.
- Ceesay M, Reid WS, Fernandes ECM, Uphoff NT (2006) The effect of repeated soil wetting and drying on low land rice yield with System of Rice Intensification (SRI) methods. Int J Agric Sustain 4:5–14Google Scholar
- Frenzel P (2000) Plant-associated methane oxidation in rice fields and wetlands. Adv Microb Ecol 16:85–114Google Scholar
- Kar S, Varade SB, Subramanyam TK, Ghildyal BP (1974) Nature and growth pattern of rice root system under submerged and unsaturated conditions. Il Riso 23:173–179Google Scholar
- Mishra A, Salokhe VM (2008b) Growing more rice with less water in Asia: identifying and exploring opportunities through System of Rice Intensification. In: Castalonge OW (ed) Agricultural systems: economics, technology and diversity. Nova Science Publishers, Hauppauge, NY, pp 173–191Google Scholar
- Mishra A, Whitten M, Ketelaar JW, Salokhe VM (2006) The system of rice intensification (SRI): a challenge for science, and an opportunity for farmer empowerment towards sustainable agriculture. Int J Agric Sustain 4:193–212Google Scholar
- Osaki M, Shinano T, Matsumoto M, Zheng T, Tadano T (1997) A root–shoot interaction hypothesis for high productivity of field crops. Soil Sci Plant Nutr 43:1079–1084Google Scholar
- Samejima H, Kondo M, Ito O, Nozoe T, Shinano T, Osaki M (2005) Charaterization of root system with respect to morphological traits and nitrogen absorbing ability in new plant type of tropical lines. J Plant Nutr 50:545–554Google Scholar
- Sato S, Uphoff N (2007) A review of on-farm evaluation of system of rice intensification (SRI) methods in eastern Indonesia. CAB Review: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 54, 2. CABI, Wallingford, UKGoogle Scholar
- Yan X, Akiyama H, Yagi K, Akimoto H (2009) Global estimations of the inventory and mitigation potential of methane emissions from rice cultivation conducted using the 2006 Intergovenmental Panel on Climate Change Guidelines. Global Biogeochem Cycles 23. doi: 10.1029/2008GM003299