Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 1999-2001
Summer 1999 Cumulative N, P, and K uptakes by grain sorghum followed a general sigmoid pattern with time (data not shown). Maximum rate of N uptake with knifing was approximately 1 lb/A/day more than uptakes for the check, and 0.5 lb/A/day more than uptake for the two surface placement methods (Figure 4). Maximum N uptake occurred near 49 days after planting for all placement treatments. Maximum rate of P uptake with knifing was approximately 15 percent greater than either broadcast or dribble placement and 50 percent greater than the check (Figure 5). Maximum P uptake rate occurred 56 days after planting for knifing but approximately one week later for the check and surface placement. This shift may be explained partially by differences in maturity. Potassium uptake followed the same sigmoid patterns as N and P uptakes (data not shown). Maximum K uptake with knifing was nearly double the maximum rate for the check (Figure 6). Even though K uptake was less than with knifing, surface applications increased the maximum K uptake rate by 50 percent above that of the check. Maximum uptake with knifing was approximately 49 days after planting, which was one week earlier than that for either surface placement and two weeks earlier than that for the check. The effect of placement on the date of maximum K uptake cannot be explained entirely by a shift in maturity. Profile Soil was a Parsons silt loam, a typical claypan soil of southeastern Kansas, testing low in available P and K, with a relatively high organic matter content. Cultivation. Dribble and knife spacings were 30 inches. Knife depth was 4 inches. N timing. N was applied half at preplant and half at the nine-leaf stage as a dribbled sidedress. Fertilizer. Preplant N, P, and K were applied as a suspension. Later N applications used UAN. Total fertilization rate was 150-100-150 (lbs/A of N-P2O5-K2O). _________________________________ Dr. Sweeney is a professor with the Southeast Agricultural Research Center of Kansas State University. ∀ Figure 4. Rate of N uptake in response to NPK suspension place- ment, Sweeney, Kansas State University. Figure 5. Rate of P uptake in response to NPK suspension place- ment, Sweeney, Kansas State University. Figure 6. Rate of K uptake in response to NPK suspension place- ment, Sweeney, Kansas State University. 4 3 2 1 0 ! ! ! 9-Leaf Boot Soft Dough 3240485664728088 Days after Planting Knife Dribble Broadcast Check N Uptake Rate, lbs/A/day 0.40 0.30 0.20 0.10 ! ! ! 9-Leaf Boot Soft Dough 3240485664728088 Days after Planting P Uptake Rate, lbs/A/day 3 2 1 0 ! ! ! 9-Leaf Boot Soft Dough 3240485664728088 Days after Planting Knife Dribble Broadcast Check K Uptake Rate, lbs/A/day Knife Dribble Broadcast Check
Fluid Journal 1996-1998
Fluid Journal 2002-2004