On-Farm Starter Fertilizer Response in No-till Corn

Even though recent experiments in the southern Corn Belt have shown that corn (Zea mays L.) yield responses to starter fertilizer are fairly common in no-till management systems, few producers in this region use starter fertilizer. Producer skepticism about the applicability of small-plot research to production situations is one reason for this lack of adoption. Several experiments have suggested that N is the most important nutrient for producing yield responses, while others have indicated that P is important as well. The objective of this research was to (i) validate at a field scale no-till corn yield and economic response to starter fertilizer and (ii) determine the relative importance of N and P in producing this yield response. During a 3-yr period, six replicated strip trials were conducted in production cornfields comparing no starter to three categories of starter fertilizer: traditional low N/high P₂O₅, medium N/medium P₂O₅, and N-only. Significant positive yield responses to starter fertilizers were observed in all six experiments. Yield differences between the three categories of starter fertilizer were minimal, and not statistically significant when averaged across locations. The average of all starter categories and experiment locations showed that starter fertilizer increased yield by 13 bu/acre. Use of starter fertilizer for no-till corn appears to be a profitable practice under production-field conditions in the southern Corn Belt. Nitrogen-only starter was the most profitable because it had the lowest material cost and produced the same yield as the P-containing starters. Research QuestionShould no-till corn producers in Missouri and other southern Corn Belt states adopt the use of starter fertilizer? Research in the region has shown fairly frequent yield responses to starter in no-till corn, and although no-till corn production systems have been widely adopted, the use of starter fertilizer for no-till corn has not. Literature SummarySide-by-side comparisons in Indiana showed that corn responds to starter fertilizer more frequently in no-till than in conventional-till production systems. Research in Kansas, Illinois, and Indiana shows relatively frequent yield responses in the 6- to 20-bu/acre range for no-till corn, and indicates that N is the most important nutrient for obtaining this reponse, with P sometimes being important as well. Similar conclusions seem to apply in the U.S. Southeast. Study DescriptionSix replicated on-farm strip trials were conducted during a 3-yr period in Missouri comparing yield with no starter fertilizer to yield with three categories of 2-by-2 placed starter fertilizer for no-till corn: (i) low N/high P₂O₅ starter (“traditional” starter); (ii) medium N/medium P₂O₅ starter; and (iii) N-only starter. Applied QuestionsWas the use of starter fertilizer profitable in these no-till production cornfields? Significant yield increases due to starter fertilizer were measured at all six locations. Each location had a starter treatment that increased yield by at least 9 bu/acre; the largest yield increase seen was 26 bu/acre. Average over all starter fertilizer categories and locations, starter fertilizer increased yield by 13 bu/acre. Even with low corn prices and the most expensive starter materials used in this study, this was enough to recover all out-of-pocket (fertilizer and equipment) costs. The cost of slowed planting associated with starter fertilizer is important but difficult to assess. Which starter fertilizer category was the most profitable? There was no difference in yield between the different starter fertilizer categories averaged across all six experiments. Therefore the N-only starter was most profitable because it had the lowest material cost. Using average corn and N prices during the period of this study (1996–1998), the N-only starter returned $20/acre above material and equipment costs. However, at the two locations where soil test P was low, P-containing starter fertilizer was slightly more profitable than N-only starter.