Yield Goal versus Delta Yield for Predicting Fertilizer Nitrogen Need in Corn

Abstract

Fertilizer N needs of corn (Zea mays L.) vary widely both among and within fields. Many states use yield goal to help determine differences in fertilizer N need, but some states have questioned yield goal–derived recommendations because of the poor correlation of yield with fertilizer N need. In this study, data from 298 previously reported experiments in five states (Illinois, Minnesota, Missouri, Pennsylvania, and Wisconsin) were combined to evaluate fertilizer N response of corn. Corn grain yield at the economically optimum N rate (EONR) was positively but poorly correlated with EONR (r2 = 0.02). This was consistent with others who have observed that maximum or optimum economic yield is a poor predictor of EONR. Our analysis indicated N supplied by the soil and previous management reduced N need from that predicted by yield alone at most locations. Delta yield (grain yield at optimum N rate minus grain yield of the control) was a much better predictor of EONR at these same locations (r2 = 0.47). A theoretically derived equation based on the delta yield concept was similarly capable of predicting EONR for corn. These results indicate that fertilizer recommendation systems that rely solely on yield or ignore yield entirely are limited to explaining less than 50% of the variation in EONR for corn. Farmers should be encouraged to monitor delta yield as a more effective indicator of EONR than actual yield. Greater understanding of the delta yield concept is needed before relying on it to predict fertilizer N requirements.

Within-field nitrogen response in corn related to aerial photograph color

“…Precision Agric (2010) 11:291-305 301 Interest in predicting delta yield during vegetative growth stages stems from previous work by Lory and Scharf (2003) who showed that EONR was related to delta yield (R 2 = 0.65) from 32 sites in Missouri. Combining the relationships identified in that research with the findings here, color differences between fertilized and unfertilized corn could be used to predict delta yield and a site-specific EONR estimated for side-dressed applications.…”

“…1). Previous work showed delta yield to be more related to EONR than to realistic expectations of yield (Lory and Scharf 2003). The EONR and delta yield were related to the four relative color indices described above using SAS PROC REG.…”

“…For some states in the USA, N management recommendations were, for many years, based on field-average yield of previous years (Rice and Havlin 1994). More recently, yield has been shown to be a poor predictor of crop N requirements in humid environments (Lory and Scharf 2003;Sawyer et al 2006;Scharf et al 2006a, b). Even where yield is somewhat related to N needs, the use of field averages results in under application of fertilizer in highyielding areas and over application in low-yielding areas of the same field (Bundy and Andraski 1995;Kitchen and Goulding 2001).…”

Variations in grain nitrogen removal associated with management practices in maize production

“…The efficiency of applied N depends on weather factors influencing soil temperature and moisture (Westerman et al 2000), soil N status, water availability, hybrid ability to take up N (Ma and Dwyer 1998;Ma et al 1999a), and plant population density of maize (Al-Kaisi and Yin 2003). Soil N supply is expected to vary among years and locations (Lory and Scharf 2003). In a humid environment such as eastern Ontario, maize yield response to N amendments is poorly correlated with soil mineral N content before planting because of great spatial and temporal variability (Katsvairo et al 2003;Ma and Dwyer 1999;.…”

“…In addition, losses as nitrous oxide (N 2 O) due to denitrification contribute to global warming, while losses as ammonia (NH 3 ) due to volatilization contribute to soil acidification when it returns to the land. Accurate fertilizer N recommendations can reduce N loss (Lory and Scharf 2003).…”