Effect of Water Stress on the Growth and Development of Amaranthus spinosus, Leptochloa chinensis, and Rice

Drought is one of the most important abiotic constraints in rainfed rice systems. In these systems, Amaranthus spinosus and Leptochloa chinensis are the dominant problematic weed species, however, published information is limited concerning the growth and development of these weeds to water stress. So the authors in this paper aimed to determine the effect of water stress on the growth and development of A. spinosus, L. chinensis, and rice.

Two studies were conducted in a greenhouse to evaluate the growth response of A. spinosus and rice and L. chinensisand rice to water stress.  The water stress treatments were 12.5%, 25%, 50%, 75%, and 100% of field capacity and the plants were grown until weed maturity (i.e., 63 days from seeding). The result showed that rice plants did not survive at 12.5% and 25% of field capacity, but both weed species survived in all the treatments. Both weed species produced a significant number of tillers/branches and leaves even at the lowest soil water content. The maximum amount of total shoot biomass produced by weed plants was 2.5 to 3 times more than that of rice plants. The soil water content to achieve 50% of the maximum aboveground biomass was 47% - 50% of field capacity for rice, whereas it was 39% and 31% of field capacity for A. spinosus and L. chinensis, respectively. A. spinosus plants responded to increasing water stress with increased leaf weight ratio, whereas the leaf weight ratio of L. chinensis decreased with increases in water stress.

In conclusion, the study findings demonstrated that A. spinosus and L. chinensis were more tolerant of water stress than the rice crop. The ability of A. spinosus and L. chinensis to produce shoot biomass under water-stressed conditions suggested that weed management strategies that can minimize weed survival in water-limited environments were needed. And these strategies may include the use of weed-competitive and drought-tolerant cultivars, high seeding rates, and optimum timing of fertilizers.

Article by Bhagirath S. Chauhan and Seth B. Abugho, from International Rice Research Institute, Los Baños, Philippines.

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Image by Duong Cong Minh, from Flickr-cc.