Excessive ammonium nitrogen can damage plants and is often an indication of overfertilization. Very high nitrate nitrogen levels may increase the risk of nitrate contamination of surface and groundwater. Phosphorus binds strongly in soil and is often unavailable to plants. Annual applications of phosphorus fertilizer are usually necessary. Deficiencies in phosphorus are often indicated by poor root, fruit or vegetable growth and a purpling of the older leaves.
Excessive phosphorus can move to rivers, ponds and lakes and promote the growth of algae and weeds.
Potassium is supplied by the clay and organic matter in native soil, however, improved plant growth is often obtained by the addition of potassium fertilizer. Sufficient potassium is thought to improve flowering, disease resistance, cold hardiness and drought survival. Potassium leaches readily from soil. Calcium in soil is readily revealed by our test. Limestone can correct a calcium deficiency, and will also neutralize soil acidity.