high rates of fertilizer and corn seed but also that application of N and P fertilizers in the furrow at low rates can Starter fertilization often is recommended to complement broadadvance silking date, increase grain yield, and decrease cast fertilization. This study evaluated no-till corn (Zea mays L.) yield grain moisture at harvest. In Iowa, for example, an Nand early growth responses to starter fertilization using precision P-K starter mixture is recommended for corn when soil agriculture tools. Strip trials, yield monitors, intensive soil sampling, global positioning systems (GPS), and geographical information sys-conditions are expected to be cooler and wetter than tems (GIS) were used to conduct 11 trials. Liquid N-P-K starter and

Foliar fertilization of crops can complement soil fertilization. Recent research showed that soybean [Glycine max (L.) Merr.] yield response to early season N–P–K foliar fertilization was inconsistent and difficult to predict. This study's objectives were to further evaluate soybean response to early season N–P–K fluid fertilizers with or without S or micronutrients and to assess the within‐field response variation. The mixtures 3–8–15 (N–P–K), 3–8–15–1 (N–P–K–S), 10–4–8, 10–4–8–1, and 10–4–8–1 plus B, Fe, and Zn were evaluated in 18 conventional small‐plot trials. The within‐field variation in response to a 3–8–15 fertilizer mixed with glyphosate [N‐(phosphonomethyl) glycine] herbicide was evaluated in eight strip trials harvested with combines equipped with yield monitors and differential global positioning systems receivers. A fertilizer rate of 28 L ha−1 was sprayed once at the V5 growth stage. There was a yield response to the 3–8–15 and 10–4–8–1 fertilizers in one small‐plot trial (260 kg ha−1) and to 3–8–15 fertilizer in another trial (360 kg ha−1). There was a small response to the 3–8–15 fertilizer across the 18 trials (93 kg ha−1). Soybean responded to 3–8–15 fertilizer only in one strip trial where the yield response was higher in acidic soil areas. No response variation was detected across contrasting soil test values or soil types within other trials. Soybean response to foliar fertilization across all production conditions will seldom offset fertilization costs. The probability of economic yield response could be increased if the fertilizer is mixed with a postemergence herbicide because application costs are reduced.

plied with other placement methods have shown inconsistent results because of a variety of factors.In-furrow starter fertilization for corn (Zea mays L.) is being pre-Response to starter fertilizer is more likely with referred to alternative starter application methods by farmers in the duced tillage. Soil tends to be cooler and wetter with U.S. Corn Belt. This study assessed corn grain yield, early growth reduced tillage and increased residue cover (Kaspar et

common practice used in some areas of the USA to improve nutrient uptake and early crop growth, even in Corn (Zea mays L.) early growth often is slower in no-tilled than soils testing high in P and K. Granulated or liquid starter tilled soils. Starter fertilization usually increases early plant growth but mixtures are applied in bands beside and below the has inconsistent effects on grain yield. This study assessed (i) starter seeds or in the seed furrow. Although potential benefits and tillage effects on corn grain yield, dry weight (DW), and N, P, and K uptake at the V5-V6 stage and (ii) the within-field variation of of starter fertilization as a complement to base fertilizaresponses. Seven replicated strip trials were conducted on fields pre-

Most agricultural fields have high soil‐test phosphorus (STP) variability. Variable‐rate (VR) technology facilitates application of different P rates over a field and could improve nutrient application and crop yield. Replicated strip trials (6–12 ha) were established at six Iowa fields and were evaluated during 4 yr to compare VR and fixed‐rate (FR) P fertilization for corn (Zea mays L.)–soybean (Glycine max L. Merr.) rotations. Fields had median Mehlich‐3 STP ≤ 20 mg P kg−1, although minimum and maximum values within each field were 4 to 18 and 22 to 62 mg P kg−1, respectively. Treatments replicated at least three times were a control, VR based on STP from grid sampling (0.06‐ to 0.08‐ha grids), and FR based on median STP. Treatments were applied with commercial spreaders and grain was harvested with combines equipped with yield monitors and global positioning systems (GPS). Phosphorus increased yield in 13 site‐years and application methods differed in 1 site‐year, when FR increased yield further. On average, VR applied 12.4% less P and reduced STP variability in five fields compared with FR. Semivariograms and SD showed that fertilization, especially VR, often reduced yield variability and seldom increased it. High STP variability at a small scale and P recommendations to maximize yield and buildup STP in low‐testing soils might explain a lack of yield differences between application methods. Although VR did not increase yield compared with FR, it managed P better and showed potential for reducing excess P loss from fields through reduced P application to high‐testing field areas.