Evaluation of Sensors for Improved Nitrogen Recommendations in Spring Wheat Production

T he issue of calcium (Ca) availability in alkaline, mineral soils has long been a matter of contention. Based on the commonly used ‘exchangeable cations’ test (ammonium acetate extraction), most Western soils are well supplied with Ca. However, in alkaline soils, a substantial percentage of ‘exchangeable’ calcium identified by this test can be in chemical forms not readily available to plants or active in soil solution. In California, calciumrelated physiological disorders such as tipburn on lettuce and blossom end rot of tomatoes and peppers are distressingly common. Vegetable growers here use significant quantities of calcium-based fertilizers and amendments to combat these disorders, and to improve postharvest quality. We conducted an extensive two-year study on soil calcium relations, attempting to answer three fundamental questions.