Controlling Soil Crusting with Phosphoric Acid to Enhance Seedling Emergence1

Abstract

AbstractObtaining adequate and uniform stands of small seeded crops is often a serious problem on soils susceptible to crusting. A study was conducted to determine if spraying dilute phosphoric acid in narrow bands along the seeded rows would increase sugar beet (Beta vulgaris L.) seedling emergence by preventing or minimizing soil crusting and provide the needed nutritional P for crop production. Dilute phosphoric acid was sprayed along rows seeded to sugar beets on a Portneuf silt loam. Several acid concentrations and P rates were applied. Stand counts were made before and after thinning, and P concentrations were measured in sugar beet petioles sampled at three dates during the growing season. Laboratory studies were conducted to determine the effects of the phosphoric acid on soil properties.Applying 69 kg P/ha as dilute phosphoric acid in liquid volumes of 650 to 1,300 liters/ha reduced crusting by increasing aggregate stability in the soil surface, increased sugar beet seedling emergence, and provided the P needed by the sugar beet crop. The acid dissolved CaCO3 and MgCO3 in the soil surface freeing Ca++ and Mg++. The cations likely reacted with PO4Ξ from the acid to form slightly soluble Ca and Mg phosphates that acted as cementing agents in soil aggregates. Using dilute phosphoric acid to reduce crusting may be equally effective for assuring satisfactory stands of other crops on calcareous soils.