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Fluid Journal : Fluid Journal 2002-2004
1 Fluid Journal Fall 2002 Do Starters Work Better in Reduced-Till Systems? by Dr. Larry G. Bundy Summary: In general, use of starter fertilizers for corn is more important in high residue reduced-till systems than in conventional-till because consistent responses to starter in no-till systems have been found even at high phospho- rus (P) and potassium (K) soil test levels. K in starter appears to be particularly important in optimizing yield in some reduced-till systems. Use of starters in reduced-till may help overcome detrimental effects of slow early growth, soil compaction, and nutrient stratification. Starters often stimulate early plant growth and development, and may lower grain moisture at harvest. Research suggests that beneficial responses to starter may be more frequent, and the size of the response greater in high residue systems, specially in no-till. Figure 1. Effect of tillage and starter NPK composition on corn yield, Bundy and Widen, 1992. Use of starter fertilizer is a well- established and often profitable practice in corn production. Current production trends toward more extensive use of no-till or high-residue tillage systems have stimulated a renewed interest in the importance of starters in reduced- till. Where soil test levels are in the respon- sive range, starters usually increase yields because plants respond to nutrients in the starter. This response is likely regardless of other management practices. At high soil fertility levels, the response to starter, when it occurs, is probably due to a placement effect that enhances early-season plant growth or helps overcome limitations to nutrient uptake imposed by the manage- ment system. Although relatively few studies have examined starter response in a range of tillage systems, data available suggest that response to starters may be more frequent and the size of the response greater in high-residue systems, especially in no-till. This conclusion is supported by numerous reports of response to starters in no-till or re- duced-till systems (Table 1). Potential reasons for these responses to starter include 1) lower soil temperatures and early-season plant growth rates, 2) increased stratification of soil nutrients, 3) increased soil compaction, and 4) higher soil moisture content in systems with little or no tillage as compared with conventional-till. COMPOSITION EFFECTS Several studies have attributed corn yield response to N in starter applica- tions while other work indicates that P and/or K in starters is needed to produce or maximize response. The geographic location of the research and the associated climate differences appear to influence the findings relative to starter composition effects. Experi- ments showing response to only starter N generally are located in southern or central USA corn producing areas while results showing response to P and/or K in starters are from central or northern production regions. RATESANDPLACEMENT Producers frequently question whether the full benefit of starters can 168 Yield-bu/A Moldboard plow No-till 164 160 156 152 148 144 140 136 10-0-0 NPK-lbs/A 10-25-0 10-0-25 10-25-25
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