Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 2005-2007
20 Fluid Journal SPRING 2007 DR. M. ALLEY, M. MARTZ, AND DR. W. THOMASON SUMMARY We conducted nine field experiments with corn to determine the optimum starter-band N rate in conjunction with the optimum sidedress N rate. Our research used blends of urea- ammonium nitrate (UAN at 30% N) solution as the N source and 10-34-0 as the P source.We varied N rates from 10 to 70 lbs/A placed ina2x2band.SoiltestPlevelsin these studies were all high and the banded P rate of 34 lbs/A of P2O5 would be expected to provide for any P fertilizer needs. In addition, we conducted starter band P application rate studies of 0, 20, 40, and 60 lbs/A of P2O5 at each site to measure corn response to varying P application rates. Typical base Timing of N and P Crucial In Achieving High Corn Yields Inadequate N availability during first six weeks after planting can result in reduced yield potentials. Optimizing nitrogen (N) and phosphorus (P) availability to corn is fundamental to achieving high yields and maximizing nutrient--use efficiency (NUE). The corn plant requires N and P soon after germination to initiate the growth of stems, leaves, and ear structures. Inadequate N availability during the first six weeks after planting can result in reduced yield potentials. Phosphorus availability is equally critical during the early stages of plant growth, and movement of P to plant roots is reduced with cold soil temperatures, which are especially prevalent under no-till conditions. For these reasons, starter fertilizers most often have contained only the N that was supplied with the base P fertilizer plus small amounts of potassium (K), sulfur (S), and micronutrients as determined by soil test needs. starter fertilizers, in addition to those already mentioned, have had analyses such as 18-46-0, although in recent years 1:1 N:P starters such as 15-15-0 have been used in areas with higher soil test P levels. Since greater total amounts of N are needed by plants than P, we asked the question: why use 1:3 or even 1:1 N:P ratio starters? Root growth response The question in the preceding paragraph is especially relevant when it is clear that plants respond to zones of both N and P enrichment by increasing root growth in the zone of enrichment, so as to maximize nutrient uptake from the zone. Barley root growth in Figure 1 clearly Figure 1. Barley root growth response to zones of nutrient enrichment, H.C. Drew. Control Phosphate High Low High Low High Low
Fluid Journal 2002-2004
Fluid Journal 2008-2009