Thirteen states associated with the Southern Extension and Research Activities Information Exchange Group-6 (SERA-IEG-6) agreed to share their soil test based P and K rate recommendations for nine major crops. The objectives were to compare fertilizer P and K rate recommendations, to look for opportunities to rationalize similar recommendations across state lines, and to examine challenges to the development of a cooperative regional approach to P and K recommendations. Mehlich-3 (eight states), Mehlich-1 (five states), or Lancaster (one state) extractions were the basis of plant available soil P (STP) and K (STK) assessment. Fertilizer recommendation philosophies (sufficiency, build and maintain, and/or hybrid) variation among the states might be the main reason behind such discrepancies. Although a few similarities in P and K rate recommendations were found, the different philosophies, numerical presentations, and extraction procedures drove important recommendation differences. Widespread adoption of the Mehlich-3 extraction procedure has not reduced variation in fertilizer P and K rate recommendations among the states. Instead, for states using Mehlich 3, soil test critical concentrations ranged from 30 to 75 mg P kg–1 and 60 to 175 mg K kg–1 for corn (Zea mays L.) grain and warm-season grass hay production. The adoption of uniform soil testing terminology, sample collection guidelines, extraction methods, and interpretations across common physiographic regions, soils, and state lines remains a challenge. Differences arise because of the different soil orders and properties, climate conditions, and resulting crop responses to added P and K fertilizers. Such differences in soil-test-based fertilizer P and K recommendations are state specific and highlight needs to examine the soil testing and recommendation process, make soil test results end-user friendly, and, when appropriate, standardize fundamental information used in the soil testing guidelines.
|Number of pages||14|
|Journal||Soil Science Society of America Journal|
|State||Published - Jul 1 2021|
Bibliographical noteFunding Information:
The authors are thankful for the partial funding provided by USDA-NRCS Grants 69-3A75-17-45 (CIG) and NR203A7500010C00.
The authors are thankful for the partial funding provided by USDA‐NRCS Grants 69‐3A75‐17‐45 (CIG), as well as USDA‐ARS Award 58‐8070‐8‐016.
© 2021 The Authors. Soil Science Society of America Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America
ASJC Scopus subject areas
- Soil Science