MISSION II  
Spread Sheet  


Mission #2
Soil Plant Nutrient Cycling and Environmental Quality 5813 The OSU soil testing lab initiated a program to establish improved P recommendations based on soil test indices. Initially, soil samples were collected from six different locations and samples were subsequently analyzed using two different extracting solutions. It was found that no other elements were limiting other than phosphorus at the locations sampled.
1. Assuming that all conditions other than soil test P were the same, determine which procedure would be best for future use in soil testing. To do this, you will need to establish the relationship between the soil test and percent maximum yield using quadratic regression and linearplateau equations. A. Determine the critical soil test level for both procedures using quadratic regression, linearplateau and CateNelson procedures. The critical level is determined by the joint from linearplateau and by taking the first derivative of quadratic regression, setting it equal to zero and solving for x. 2. Once the ideal analytical procedure and critical soil test levels have been determined you must now evaluate data obtained at each of these sites where phosphorus fertilizer rate studies were conducted. In each case, N, K and other micronutrients were applied in adequate but not excessive amounts and P was applied as triple superphosphate (0460) at rates of 0, 20, 40, 80, 120, 160 and 200 kg P/ha. In each experiment, P was applied broadcast before planting and was disk incorporated. Results from these experiments were as follows; Farmer P rate Grain Yield kg/ha kg/ha ____________________________________ 1 0 915 1 20 1350 1 40 2212 1 80 2715 1 120 3210 1 160 3399 1 200 3601 2 0 1500 2 20 2450 2 40 2850 2 80 3250 2 120 3550 2 160 3590 2 200 3570 3 0 2316 3 20 2860 3 40 3340 3 80 3690 3 120 3604 3 160 3606 3 200 3601 4 0 3180 4 20 3360 4 40 3450 4 80 3598 4 120 3502 4 160 3622 4 200 3518
Assuming that the soil test values obtained for each individual farmer are representative of larger populations with the same value; A. Determine the optimum fertilization rate for each farmer using quadratic regression, linearplateau and CateNelson procedures. B. Using the price of wheat at 0.13$/kg and the cost of P/kg applied at 0.50$, what rate of P would you recommend to these same farmers using quadratic regression. 3. Briefly discuss the results obtained from #1 and #2 in terms of how we make fertilizer recommendations to farmers, and how you might change the sequence of events to improve upon soil test/correlation/calibration/recommendation work. 4. Based on the information collected, establish a table which will recommend P fertilizer rates using soil test indices (range) and percent sufficiency (see your Soil Fertility Handbook) 5. Why is it valuable to have at least two extremely high rates (beyond that which farmers would commonly apply) in fertilizer rate evaluation studies. 1._________________________________________________________________________ CL  critical soil test level 2.
SAS PROGRAM data one; input farmer x bray y; /* farmer mehlich bray yield */ /* substitute bray for x, next time through & rename current x back to mehlich */ cards; 1 7 10 1100 2 11 15 1450 3 16 20 2016 4 28 26 3400 5 31 31 3630 6 35 35 3549 PROC PRINT; /* LINEAR PLATEAU */ PROC NLIN DATA = ONE BEST = 3; PARMS B0=100 to 500 by 100 B1=50 to 200 by 20 NJOINT=15 to 30 by 2; IF X<NJOINT THEN DO; MODEL Y = B0 + B1*X; DER.B0=1; DER.B1=X; DER.NJOINT=0; END; ELSE DO; MODEL Y=B0+B1*NJOINT; DER.B0=1; DER.B1=NJOINT; DER.NJOINT=B1; END; FILE PRINT; IF _obs_ =1 AND _MODEL_ =0 THEN DO; PLATEAU = B0 + B1*NJOINT; PUT PLATEAU=; END; PLATEAU=B0+B1*NJOINT; ID PLATEAU; OUTPUT OUT = NEW P = PRY PARMS=B0 B1 NJOINT SSE=SSE; RUN; PROC PLOT; PLOT Y*X='+' PRY*X='*'/OVERLAY; RUN; PROC MEANS NOPRINT; VAR Y SSE B0 B1 NJOINT PLATEAU; OUTPUT OUT = NEW2 N = TDF MEAN = Y SSE B0 B1 NJOINT PLATEAU CSS=CSST; DATA NEW3; SET NEW2; INTERCPT=B0; SLOPE=B1; JOINT=NJOINT; RSQ=(CSSTSSE)/CSST; EDF=TDF3; SSR=CSSTSSE; MSR=SSR/2; MSE=SSE/EDF; F=MSR/MSE; PROBF=1(PROBF(F,2,EDF)); KEEP INTERCPT SLOPE JOINT PLATEAU RSQ F PROBF; PROC PRINT; RUN;
