Electrical Conductivity and Sodium Adsorption Ratio Changes Following Annual Applications of Animal Manure Amendments

Abstract

The objective of this research was to evaluate the effect of five annual applications of animal manures on soil electrical conductivity (EC) and sodium adsorption ratio (SAR) estimated from saturated soil-paste extracts. Swine effluent (SE), beef manure (BM), and anhydrous ammonia (AA) were annually applied at loading rates of 0, 56, 168, 504 kg N ha-1 to a irrigated conventionally tilled, continuous corn (Zea mays L.) cropping study in the Oklahoma panhandle. The cumulative effects of five annual N applications were examined in 2000. Changes to soil EC and SAR were observed in 2000 at the 0-15 cm soil depth. Beef manure and SE contributed 90 kg and 115 kg Na ha-1 yr-1, respectfully at the highest N loading rate application. Manure EC was 12.7 and 9.5 dS m-1 for BM and SE, respectfully. Sodium adsorption ratios increased with SE additions at the high N loading rate application; however SAR decreased with the high AA loading applications, while SAR remained unchanged with BM applications. The SAR increased linearly with SE additions; whereas SAR decreased linearly with AA additions. Slow increases of SAR with high SE loading above the control in manure-applied treatments indicate potential for the soil to become sodic and disperse. Soil EC has not been adversely affected by BM or SE additions; however, EC levels increased 2.35 dS m-1 with the high AA loading rate above all other treatments. Soil EC levels have increased as a result of the high AA loading that future crop growth may be affected.