Evaluation of Corn Yield & Nutrient Composition Response to P & K

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Objective

Assess corn yield response to phosphorus (P) and potassium (K) fertilizer applications.
Assess the effect of P and K fertilizer applications on corn plant nutrient concentrations at V4, V10-12, VT-R1 and in the harvested grain.

Study Description

Plot Layout:		4-row randomized small plots
Replicates:		4
Location:		Arlington, Wis.
Tillage:		No-till
Rotation:		corn, soybean
Treatments:		Broadcast in spring of 2014

4 rates of P (0, 30, 60, 90 lbs P₂O₅) as 0-46-0 at each rate of K (0, 40, 80, 120, 160 lbs K₂O/acre) as 0-0-60
The same treatments were applied to the same plots for 4 consecutive years.


Soil Tests:		Prior to application in spring 2014 Soil test P: 8-21 ppm (v. low to high) Soil test K: 51-94 ppm (v. low to low)

Hail Damage:		A hail event took place on August 1. Photo (see below) was taken on August 27.

Results

When P rates were ≥ 60 lb P₂O₅/acre, yield was significantly greater than where no P was applied (Table 1).
There was a significant yield response to K applied at rates up to 80 lb K₂O/acre, which had an average soil test of 65 ppm K. Yield increases at rates ≥ 80 lb K₂O/acre were greater where P was applied compared to where P was not applied (Table 1).
In previous years of the study there was no yield response to P application. These results suggest that at soil test K levels below 65 ppm, K is most limiting. When soil test K is greater than 65 ppm, P begins to limit yield.
Soil sampling in 2-inch increments demonstrated that soil test P and K are highly stratified in this long-term no-till field.
Tissue nutrient concentrations at V4, V10, and R1, as well as grain and silage nutrient composition, are not available at this time.

Table 1. Effect of no-till surface broadcast P₂O₅and K₂O rates applied in spring 2011, 2012, 2013, and 2014 on 2014 corn grain yield at Arlington.

P₂O₅ rate	K₂O rate, lb/acre
P₂O₅ rate	0	40	80	120	160	Mean†
lb/acre	——————— bu/acre ————————
0	40	156	194	192	190	155 b§
30	28	150	215	211	204	162 ab
60	27	152	230	235	210	171 a
90	36	157	205	243	208	170 a
Mean‡	33 d	154 c	211 ab	220 a	203 b

† P₂O₅ rate p = 0.02.
‡ K₂0 rate p < 0.01. P₂O₅ rate x K₂0 rate p = 0.08. CV = 11%.
§ Mean values followed by the same lowercase letter are not significantly different at the 0.10 probability level.

Research conducted by Carrie Laboski, Professor & Extension Nutrient Management Specialist, University of Wisconsin-Madison, as a part of the Pioneer Crop Management Research Awards (CMRA) Program. This program provides funds for agronomic and precision farming studies by university and USDA cooperators throughout North America. The awards extend for up to 4 years and address crop management information needs of Pioneer agronomists and customers, and Pioneer sales professionals.

2014 data are based on average of all comparisons made in one location through Dec 1, 2014. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.