Survey of the Silicon Status of Flooded Rice in Louisiana

Low Si content in rice (Oryza sativa L.), sugarcane (Saccharum officinarum L.), and other Si-accumulating crops can adversely affect crop performance by increasing susceptibility to abiotic and biotic stresses. Although it is generally assumed in the United States that soils containing appreciable amounts of silicate clays supply adequate Si to meet crop demands, there is little evidence to support this assumption. A survey was conducted to assess the Si status of rice plants at mid-tiller (Y-leaf) and at harvest (straw) in 97 rice fields located throughout the rice-growing regions of Louisiana. On average, Y-leaves contained 30.5 +/- 7.8 g Si kg(-1), whereas mature rice straw contained 54.7 +/- 12.7 g Si kg(-1). Low early season Si assimilation occurred in nearly all rice fields, whereas only 36% contained mature straw with <50 g Si kg(-1), a level commonly used to indicate sufficiency. Late-season deficiencies were limited to fields in extreme southwest Louisiana where soils tend to be strongly acidic and have a long history of rice production.