Fertilizer Placement for Small Grains in Relation to Crop Stand and Nutrient Efficiency in Nebraska1
- R. A. Olson and
- A. F. Dreier2
Time and method of fertilizer nutrient application have been found to markedly influence stand and growth of small grains in Nebraska. Severe stand reductions and yield losses have been noted as a result of moderate rates of N as well as K applied with the seed. These losses do not occur every year, nor are they uniform across the state in the years when noted. On the other hand, efficiency of applied P usually has been much greater when applied with the seed than by other methods.
Investigations in the field and constant temperature laboratory suggest a low moisture level at which the most serious damage of fertilizer salts to germination occurs, but full germination is not assured at any soil moisture level without a surface increment to leach fertilizer away from the seed. Emergence loss from N adjacent to the seed at low moisture level is in direct proportion to the time interval before rain or irrigation raises the level. In general, N materials are more detrimental per unit weight than K, and the latter more than P. Damage to germination under critical soil moisture is apparent at 10 lbs. N/acre, increasing to the point of stand elimination with 160 lbs. N/acre. Among N carriers, CaCN2 and NH4OH are most deleterious to germination followed by CO(NH2)2 > NaNO3 > KNO3 > (NH4)2SO4 > NH4NO3. Straight carriers of phosphate cause little damage, but ammonium phosphates of 1:1:0 ratio are harmful when placed with the seed under conditions of limited moisture; the damage is less with pelleted than finely ground material. Fertilizer and seed need not be in immediate contact for germination inhibition, as evidenced by appreciable migration of N and P to the imbibing seed.
Soil microorganisms are in part responsible for fertilizer injury to germinating seed, occasioned by their greater tolerance of low moisture supply and high salt concentration. Seed treatment at the lower moisture levels alleviates but does not eliminate the fertilizer detriment.
Phosphorus placement with the seed of small grains is desirable in the drier regions so long as the N concurrently added with the seed does not exceed 10 or 15 lbs./acre. Supplementary N is essential to maximum P fertilizer utilization, but much of it should be applied separate from the seed.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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