Interaction of Manure and Nitrogen or Starter Fertilizer in Northern Corn Production

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Nutrient availability of applied manure may be reduced under the cool early season climatic conditions found in the far northern corn (Zea mays L.)-growing environments. This study evaluated the effectiveness of combining applications of starter and N fertilizers with manure on improving corn growth and soil nutrient levels in northern Wisconsin from 1979 to 1981. Residual effects of treatments also were evaluated from 1982 to 1983. Main treatments of five rates of manure (0, 19, 33, 60, and 121 tons/acre on a wet weight basis) were arranged in a split-strip plot design with split plot treatments of four rates of N fertilizer (0, 40, 80, and 120 lb N/acre) and strip plot treatments of two starter fertilizer rates (0 and 150 lb/acre of 6-24-24). Although application of manure and N fertilizer consistently increased silage dry matter yields, application of starter fertilizer affected yields in only 1 of the 3 yr in which treatments were applied. Climatic conditions alone were not sufficient to explain crop response to starter fertilizer. No interactions between manure and starter fertilizer or manure and broadcast N fertilizer applications were observed. Research Question In northern regions of the Corn Belt, cool spring temperatures may affect early season nutrient availability from dairy manure applications. Possible management of this short-term nutrient need may require additional applications of N or starter fertilizers. This study was established to determine the seasonal and residual effects of combining applications of starter or N fertilizers with manure on corn silage and soil nutrient levels. Literature Summary Lower soil temperatures experienced in northern climates decrease rates of N mineralization from manure applications and reduce plant availability of other nutrients, such as P. Annual corn yield response to application of starter fertilizer is inconsistent in the northern corn-growing states, but often results in improved early season growth. Factors affecting crop response to starter fertilizer include soil type, tillage method, rate and composition of starter fertilizer, and planting date. Combined applications of broadcast N fertilizer and manure have resulted in higher corn yields by overcoming the relatively low initial N availability from manure and by the addition of other nutrients contained in manure. Study Description Corn hybrid Warwick SL207 (75 d relative maturity) was grown for each year from 1979 to 1983 at Ashland, WI. Treatments were combined or applied separately for the 1979 to 1981 seasons and residual treatment effects examined during the 1982 and 1983 seasons. Soil: Manistee sandy loam (sandy over clayey, clayey, mixed, frigid Al-fic Haplorthod) Treatments: 0, 19, 33, 60, and 121 tons/acre dairy manure 0, 40, 80, and 120 lb N/acre N fertilizer 0 and 150 lb/acre starter fertilizer (6-24-24) Treatment Design: Split-strip plot design in randomized complete blocks with four replications Weed control: Alachlor (2 qt/acre) and atrazine (2 lb/acre) Applied Questions Did the application of N or starter fertilizers in combination with manure increase corn silage yields? Combining N or starter fertilizers with manure did not consistently increase silage yields beyond yields obtained with each fertility source applied separately. Yield advantages of manure and N fertilizer applications were consistent from year to year (Fig. 1), although annual yield response to manure during years of application and subsequent residual cropping seasons was higher because of crop response to manure P and K and possibly to other effects of manure on soil physical and biological properties. Application of starter fertilizer raised yields in 1 of the 3 yr in which treatments were applied (Table 1). Variability in early and late season climatic conditions and differences in annual crop nutrient demand from variable plant populations may have been factors limiting corn response to starter fertilizer applications. Interpretation of the results is complicated by the accumulation of soil P and K and organic N after repeated manure applications to the same plot area. This accumulation possibly reduced crop response to starter applications and also had significant positive residual effects on subsequent crop yields. Recommendations The results of this study do not provide a clear resolution to the need for annual applications of starter fertilizer in combination with manure applications under northern climatic conditions. The application of N fertilizer may be advisable, however, when used in situations where low rates of manure (less than 33 tons/acre) have been applied or when minimal residual effects from previous manure applications are expected. Table 1. Effect of starter fertilizer on silage yield, 1979 to 1983. Years treatments applied Residual years Starter 1979 1980 1981 1982 1983 --------------------tons/acre-------------------- Without 3.4 4.2 3.4 1.9 3.3 With 3.3 4.1 3.8 1.8 3.4 LSD (0.05) NS† NS 0.3 NS NS † NS = not statistically significant. Figure 1Open in figure viewerPowerPoint Yield response to manure and N fertilizer applications for 1979 to 1981. Bars indicate LSD (0.10) for comparison of N fertilizer treatment means at each rate of manure application.