Use of Nitrogen Fertilizers

Nitrogen Deficiency

• Nitrogen deficiency is generally characterized by a pale yellow-green color, becoming increasingly pale and yellowish with greater severity. The oldest leaves closest to the base of the plant display the most severe discoloration, and may wilt and die. A lack of nitrogen can be caused by a variety of factors, including intensive cropping and frequent heavy rains, which can cause nitrogen to leach out of the soil. Also, a low pH, which indicates acidic soil, can make it difficult for plants to absorb nitrogen. Applying nitrogen fertilizers is the most common way to combat deficiency.

Nitrogen Fertilizers

• Nitrogen fertilizers are available in many forms. Organic materials like manure and decaying plant matter add nitrogen to soil, but they are usually more effective when combined with a non-organic nitrogen source. In commercial fertilizers, look for the words "ammonium," "nitrate" or "urea" on the packaging; these indicate nitrogen fertilizers.

Considerations

• Timing and quantity of nitrogen fertilizer are important considerations. Nitrogen fertilizer should be applied as close as possible to the period of greatest crop growth, which may be between May and July, depending on where you live and what you are growing. Fertilizers can also be applied in fall or earlier in spring, but with a greater risk of losing nitrogen to heavy rains and leaching. Application rates should not exceed 40 lbs. of nitrogen per acre.

Soil Testing

• If you are unsure of the nitrogen levels in your garden or lawn, a soil test from your nearest University Extension office is the best way to find out. The test results will include the levels of nitrogen and other elements, as well as pH levels and recommendations for fertilizers and amendments.