Silicon Status of Louisiana Soils Grown to Different Field Crops.

Adequate silicon (Si) nutrition in plants has shown decreased susceptibility to fungal pathogens and insects, amelioration of abiotic stresses, increased growth and yield, and enhanced nutrient uptake. Positive effects on the chemical and physical properties of the soil have also been observed. Louisiana is one of the few states in the nation where rice and sugarcane (both Si accumulating crops) are produced, but little is known about the Si status of the different agricultural soils of the state. Hence, this study was initiated to survey the extractable Si in the agricultural soils of different parishes of Louisiana and determine the impact of crop production systems and soil type on soil Si levels. More than 10 samples were collected from each of the agrarian parishes along the banks of the Mississippi, Arkansas and Red Rivers, and areas in the Gulf Coast Prairies and Marsh. These areas are currently planted to different field crops including cotton, sugarcane, corn, soybean, rice and wheat. Soil pH, extractable P, K, Ca, Mg, S, Cu and Zn, and soil Si extracted using seven solutions were determined in each of these samples. The soil Si extracted using 0.5 M acetic acid solution ranged from 3 to 300 mg kg-1. The amount of Si extracted by the different solutions was in the order of citric acid > acetic acid (24hrs shaking) > acetic acid (1 hr shaking) > sodium acetate > NH4OAc > calcium chloride> deionized water. Silicon extracted by water showed poor correlations with Si extracted by other solutions. Previous studies showed a soil test Si of <30 mg kg-1 using 0.5 M acetic acid solution is considered low. By applying this interpretation on the initial results of soil Si status survey conducted in this study, many production areas in Louisiana can potentially benefit from Si fertilization.