Placement Methods for Improved Efficiency of P and K Fertilizers: A Review

Efficient fertilizer placement is attracting increasing interest as tillage systems change, economic profitability becomes tighter, environmental awareness increases, and improvements are made in application equipment. Efficacy of various placement methods for fertilizer P and K is highly dependent on soil test level, crop, soil texture, tillage system, and climatic conditions. At high soil test levels, crop yield response differences due to placement methods are rare. At low soil test levels, corn (Zea mays L.) yields obtained from band (2 × 2 in.) placement are seldom surpassed by other placement methods. Surface strip and deep subsurface bands (6 to 8 in.) have outperformed broadcast applications, particularly in years when precipitation is insufficient, soil test levels are low, or reduced tillage is used. Placement of fertilizer directly with the corn seed is not recommended on sandy soils if seed‐zone soil moisture is low. Soybean (Glycine max L.) has responded more consistently to broadcast than to band applications in limited studies. Small grains generally have responded better to band applications with the seed or knifed in to a 4‐ to 5‐in. depth, especially under drier conditions. When soil tests are low, soil moisture and/or precipitation is limiting, or land is rented, and when fertilizer efficiency and economic return are to be maximized, localized placement methods giving a zone of high fertilizer concentration within the effective rooting area should be strongly considered for corn and small grains.