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Fluid Journal : Fluid Journal 2002-2004
Early Spring 2004 Fluid Journal 2 starter to reduce possible ammonium toxicity that might damage germinating seeds in young plant roots. Such inhibitors could also reduce nitrogen losses by slowing urea hydrolysis. K Starter Recently, the incidence of early- season K deficiencies in corn under reduced-till has become more and more common in many states, even when soil test K levels are considered to be adequate. Research in Iowa by Dr. Antonio Mallarino and Kansas by Dr. Barney Gordon has confirmed the need of K in starter to offset the effects of early-season stress. Amounts of K needed may not be large but have significant effects on yields, even when soil tests are very high. Starter Placement Research supported by the Fluid Fertilizer Foundation (FFF) has shown that high N starters can be effective in placement configurations other than the conventional 2 x 2 placement. Studies in both Maryland and Kansas on high P-testing soils (Figures 1 and 2) have demonstrated that dribble placement of Figure 3. Soil distribution of bio-available P after dribble applications of fluid starter 2 inches side of seed row, Kovar, National Soils Tilth Laboratory. Table 1.Effects of N concentration on starter response in irrigated corn 2-year Avg. Lb/A N-P2O5-K2O bu/A Control, no starter 159 5-15-5 187 15-15-5 192 30-15-5 210 45-15-5 210 60-15-5 209 Gordon, Kansas State U. starter on the soil surface 1 to 2 inches to the side of the row can produce yields essentially equal to 2 x 2 placement. However, surface banding directly over the row was substantially less effective, possibly due to migration of urea into the soil surrounding the germinating seed. Surface-applied P The fact that surface starter placement is effective as measured by P uptake and yield implies that surface applications of P are not as immobile as long assumed, but rather that some degree of P mobility must exist. Evidence of such mobility has been provided in recent FFF-supported research by Dr. John Kovar of the National Soil Tilth Laboratory in Ames, Iowa (Figure 3). A significant amount of P mobility was detected beneath surface dribble bands of starter 43 days after application on a silt loam soil. Substantial P downward movement was detected with both 15-30-10 and 60-30- 10 starter rates. With the evidence of P mobility from Kovar's research and the excellent responses to surface dribble starter in Gordon's, Mulford's, and Kovar's field studies, there is no question that the N and P are getting to the plant roots. Sulfur would likely show similar mobility. However, the mobility of K and Zn in these high ammonium bands has not been determined. One has to wonder if the concentrations of ammonium might also affect the ability of these nutrients to move in the soil because of saturation of the soil's exchange sites with ammonium ions beneath the surface bands. Continuing Work Research on the efficacy of fall- applied surface bands and surface starter bands for wheat is under way at locations in the U.S. and Canada with support from the FFF. Fall application
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