2015
Developing the first phosphorus and potassium plant tissue test interpretations for corn and soybean in Iowa
Contributor/Checkoff:
Category:
Sustainable Production
Keywords:
GeneticsGenomicsSeed quality
Lead Principal Investigator:
Antonio Mallarino, Iowa State University
Co-Principal Investigators:
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:

The general goal of this project is to evaluate the value of plant-tissue testing for phosphorus and potassium in soybeans and corn to assess deficiencies and guide fertilization. There had been a very strong push by some private laboratories and companies for using tissue testing, some suggesting that P and K deficiencies are widespread based on tissue testing, although soil testing indicates otherwise. Research studies relationships between plant tissue-test results and grain yield response to P and K fertilization for several varieties and hybrids and develops the first P and K plant tissue test interpretations that producers and crop consultants can use, if it proves to be a reliable diagnostic tool.

Key Benefactors:
farmers, agronomists, Extension agents, consultants, testing labs, diagnostic clinics

Information And Results
Project Deliverables

Provide P and K plant tissue test interpretations for corn and soybean in Iowa.

Final Project Results

The project showed that the concentrations of P and K in young plants sampled at the V5-V6 growth stage and mature leaves sampled at the R2-R3 stage do provide an indication of the potential soybean grain yield response to fertilization. The project identified critical concentration ranges, which distinguish between conditions of nutrient deficiency and likely response to fertilization from conditions of adequate levels and unlikely response. The determined tissue critical concentration ranges for P were 0.33 to 0.41 % P for young plants sampled at the V5-V6 growth stage and 0.35 to 0.47 % P for mature leaves sampled at the R2-R3 stage. The determined tissue critical concentration ranges for K were 1.89 to 2.26 % K for young plants and 1.56 to 1.99 % K for mature leaves. Previous research in Iowa or the north-central region had not determined P or K critical concentrations for soybean plant tissue at the V5-V6 stage of growth, so the concentrations determined by this project are the first reported. Literature from other regions for soybean leaves at early or intermediate reproductive stages suggest sufficiency ranges of 0.26 to 0.6% P and 1.5 to 2.5% K. Therefore, the critical concentration ranges found by the project for P or K in soybean leaves is narrower and more useful than sufficiency ranges suggested in the literature.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.