Corn yield response to sub-surface banded starter fertilizer in the U.S.: A meta-analysis

Sub-surface fertilizer application at planting (i.e., starter fertilization) is a common practice in U.S. corn (Zea Mays L.) production to improve early-season nutrient uptake, nutrient use efficiency, and plant growth, especially under cool and moist spring soil conditions. However, yield increases from starter applications can vary across production systems and environments. Here, we use a meta-analysis approach to quantify and generalize corn yield responses to sub-surface starter fertilizer applications in the U.S. and to understand the management and environmental factors that drive variability in corn yield response across previously published research. This meta-analysis summarizes peer-reviewed research from the U.S. published between 1990 and 2019. The dataset encompasses 474 observations from 23 studies conducted in various locations and includes information regarding management practices used and soil and weather conditions. We calculated effect size as the natural log of the response ratio, with the response ratio determined as corn yield with a starter fertilizer application containing nitrogen (N) and phosphorus (P) or N, P and potassium (K) relative to corn yield without a starter fertilizer application. Additionally, we investigated the impact of potential moderator variables on corn response to sub-surface starter fertilization (e.g. agronomic practices, soil properties, and weather conditions). On average, fertilizer sub-surface applied in the furrow or banded 5 cm to the side and 5 cm below the seed at planting increased corn yield by 5.2 %. Corn response to starter fertilization was consistent across many agronomic and environmental conditions including different tillage systems, previous crops, soil textures, and planting season weather conditions. Yield benefits decreased with increasing soil test P and K levels. Nevertheless, yield increases from starter fertilization occurred with soil test levels up to 500 % and 300 % of the P and K critical levels, respectively. In addition, corn yield benefits from starter fertilization decreased as corn planting density increased and as corn yield level decreased. Overall, this meta-analysis provides support for the use of sub-surface starter fertilizer applications to improve corn yield.