Soil testing pays

Authors: Young, Eric

Submitted to: Progressive Forage Grower
Publication Type: Trade Journal
Publication Acceptance Date: 9/26/2020
Publication Date: 10/30/2020
Citation: Young, E.O. 2020. Soil testing pays. Progressive Forage Grower. 2020.

Interpretive Summary:

Technical Abstract: Agronomic soil testing is a critical farm practice because it’s the main way to estimate plant-available crop nutrients. As such, it should form the basis from which fertilizer, manure, lime, and other fertility management decisions are made. Proper soil testing and interpretation of results are essential for optimal crop enterprise budgeting and farm profitability. The cost of a basic agronomic soil test ranges from $10 to 20/sample in the US. Since soil samples should be collected once every three years, the average cost is approximately $0.67/acre/yr. Proper sampling is essential for results to be meaningful. Land grant universities typically recommend that individual soil samples represent no more than 10 to 20 acres of field area. Soil test results should be tied to historical or current research relating specific nutrient levels to measured crop yield in differing soils, so the likelihood of a crop response from added nutrients can be gauged appropriately (termed ‘soil calibration’). Effective testing pays whether a crop needs fertilizer or not since both nutrient deficiencies and excesses are revealed, allowing fertilizer and manure nutrients to be applied where and when they are needed. Soil pH profoundly affects plant health and nutrient availability and must be carefully managed for optimal nutrient use efficiency and microbial cycling of nutrients. In fields with a substantial manure application or fertilizer history, available phosphorus (P) and potassium (K) concentrations are often well above optimum to the extent that no purchased P or K is required for optimum yields. In addition, corn nitrogen needs are often much lower in fields receiving manure, which can also be easily and cost-effectively assessed through routine soil testing. Standard agronomic testing in addition to new soil biology/health measures will play increasingly important roles in the dairy and agricultural industry at large going forward given food security and environmental concerns.