Deep phosphorus fertiliser placement and reduced irrigation methods for rice (Oryza sativa L.) combine to knock-out competition from its nemesis, barnyard grass (Echinochloa crus-galli (L.) P.Beauv)

Authors: Gealy, David

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2015
Publication Date: 4/22/2015
Publication URL: http://handle.nal.usda.gov/10113/61176
Citation: Gealy, D.R. 2015. Deep phosphorus fertiliser placement and reduced irrigation methods for rice (Oryza sativa L.) combine to knock-out competition from its nemesis, barnyard grass (Echinochloa crus-galli (L.) P.Beauv). Plant and Soil. 391:427-431. DOI 10.1007/s11104-015-2478-5.

Interpretive Summary: Rice farmers are experiencing more and more roadblocks to production and profitability worldwide because of limitations in availability of abundant irrigation water, affordable fertilizers, and adequate weed control tools. This paper reviews recent discoveries by a research team from Sri Lanka and Australia, who demonstrated an interesting, and potentially more affordable and sustainable production approach for phosphorus-starved soils that saves water and improves weed control by placing phosphorus fertilizer deep in the soil where only the rice roots can reach. Their system dramatically increased the competiveness of rice against barnyardgrass, one of the most devastating weeds of rice worldwide. It stunted the growth of barnyardgrass plants, but maintained the productivity of rice.

Technical Abstract: Productivity of rice is increasingly being constrained by limitations in the quantity, quality, and cost of water and nutrients, and competition from weeds. This is a ‘commentary’ on the recent work of Weerarathne et al. (2015). They reported new discoveries from greenhouse experiments that showed that precise deep placement of phosphorus (P) fertilizer 15 to 20 cm below ground level in low-phosphorus-containing soils irrigated using methods such as “alternating wetting and drying” that reduce water use, dramatically increased the competiveness of rice against its most widespread and costly weed pest, barnyardgrass (Echinochloa crus-galli). The growth of barnyardgrass was severely stunted because its roots did not reach the depth necessary to readily access the P fertilizer. In contrast, rice plants maintained robust growth under these conditions because they adapted by lengthening their roots and adding more fine roots, which allowed them to reach, take up, and utilize the deeply placed P.