The Importance of Early Season Phosphorus Nutrition

Phosphorus (P) fertilization is a major input in crop production on the Great Plains, as many soils lack sufficient P for effective crop production. To optimize crop nutrition, P must be available to the crop in adequate amounts early in the growing season. Phosphorus is needed from the earliest stages of crop growth, because it is important in nearly all energy-requiring processes in the plant. Phosphorus stress early in the growing season will reduce crop productivity more than P restrictions later in the year. Plants have adapted to increase their ability to access P and avoid deficiencies. When under P stress, plants will use their resources to extend their root system to improve the chance of contacting P. Some plants can modify rhizosphere pH or excrete organic acids to increase the uptake of P. Plants such as canola or wheat can increase root proliferation in high-P regions to enhance P uptake while others will form associations with vesicular arbuscular mycorrhizae. Plants differ in strategies adopted and in efficiency of P absorption. Understanding how different plants respond to P deficiencies and fertilization can help in designing P management practices most suited to each crop type. Phosphorus placement in or near the seed-row helps supplies P to the crop early in the growing season. Other ways of managing P could include increasing seed concentrations of P, using tillage system and crop sequencing to improve mycorrhizal activity, or maintaining adequate P levels in the soil. Since plants differ in their ability to access P from the soil and fertilizer applications, different practices may be needed for different crops. We need to more accurately predict early P supply from the soil to avoid over-fertilization or crop deficiencies. By fertilizing only where P limits crop production and by improving fertilizer efficiency, we can optimize economic of crop production and avoid environmental problems