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Fluid Journal : Fluid Journal 1993-1995
1 Fluid Journal Fall 1993 t appears we once again have entered an era of increased interest in starter fertilization. Today's high yields translate into increased residue production and reduced tillage is leaving more of that residue on the surface, often resulting in nutrient stratification. Thus the increasing appeal of starter methodology that offers producers precise placement and high efficiency. Equipment manufacturers have also made great progress in offering planter banding equipment that is durable and can handle residue with a minimal increase in planting time. Nutrient deficiency One symptom we've been finding in today's high residue farming systems that stands out is inadequate early- season nutrition of corn, especially during years with cooler than normal springs. Such a year, for example, was 1992 in the upper Midwest. The results of a survey of 80 corn fields at approximately the V5 growth stage in Iowa, Minnesota, and eastern South Dakota are summarized in Table 1. Over 50 percent of the fields in the survey tested insufficient in P while 75 percent were insufficient in at least one nutrient. The fields selected represented a cross section of soil parent materials, soil test levels, tillage systems, and fertilizer use. Best combinations The question then becomes which are the best combinations of nutrients to use in planter-applied fertilizers? The relative importance of specific nutrients appears to vary with geography and cropping system, making summarizing by Dr. PaulE. Fixen and Dr. Raun D.Lohry AL AL AL AL ALook atStar ook atStar ook at Star ook at Star ook at Starters on Corn ters on Corn ters on Corn ters on Corn ters on Corn IHow is switching to reduced tillage affecting fertilizer placement in row crops? generalizations difficult. Best NP combinations in starters for corn found by Touchton12 in 1988 on the sandy Coastal Plain soils of Alabama, which tested very high in available P, were 40-20 or 60-0 (N- P2O5, lbs/A). Fertilizers were formulated from UAN, phosphoric acid, and water and mixed in the upper 2 to 4 inches of soil in the row area. In each of the four years, N improved early-season plant growth, while P added with N had a positive effect on early growth in only one year. Starter fertilizer increased corn yields by up to 39 bu/A when averaged over the four years. In summarizing research on optimum N and P rates for starters in the Southeast, Zublena14 stated: 1) N and P rates in corn starters can affect grain yields, 2) starter N rates should be higher than the conventional use rate of around 10 lbs/A, 3) optimum N rate appears to be between 30 and 40 lbs/A, 4) on high P testing soils, starter P is less critical for yield, with optimum P rates around 10 lbs/A, and 5) on soils testing medium or low in P, higher starter P rates may be beneficial. Corn response to N in starter fertilizer has also been common in the central Midwest. 1990 research in Indiana showed that N is the nutrient responsible for many responses to starter fertilizer in conservation tillage. However, Purdue University guidelines suggest that the amount of N + K2O in a 2 x 2 band for corn not exceed 40 lbs/A. A three-year (1989-1991) cooperative research effort between the University of Nebraska and the University of Minnesota7,9,13 showed considerable flexibility exists in the N to P ratios of starters in these corn-producing states (Table 2). Some treatments were included at 7 site-years while others were included at 11 site-years. Fluid starters were applied in a 2 x 2 band in conservation tillage (not no-till or ridge- till) on soils testing low or medium in P. Yields of the no-starter checks ranged from 110 to 174 bu/A, with an average of 149 bu/A. The greatest early growth enhancement occurred with the 1:1 N:P2O5 ratio. The 1:3, 1:2, and 1:1 ratios all had very similar effects and were essentially agronomically equal. The 2:1 and 3:1 ratios produced less early growth enhancement than the lower N starters. Grain yield increases were similar for all ratios, with the possible exception of the 3:1 ratio, Table 1. Corn nutrient concentrations at the V5 growth stage in the upper Midwest in 1992. Sufficiency Measured % of Fields Nutrient Level (V5) Range Insufficient N 3.40 1.60-4.70 23 P 0.35 0.14-0.63 53 K 2.70 1.00-6.30 26 S 0.16 0.11-0.29 31 Zn, ppm 20 16-46 8 80 fields tested: 35 in IA, 30 in MN, 15 in SD. In each field, 32 plants were collected from a 100-ft x 100-ft area of the major soil series.
Fluid Journal 1996-1998