Ham and Caldwell (1978) reported that fertilizer P increased soybean production but placement had no Improved P and K management systems for no-tillage soybean significant effect on yield and P uptake. The Ham and [Glycine max (L.) Merr.] may be needed to increase yield and profits. This study evaluated the response of soybean to fertilizer P or K rates Caldwell (1978) paper did not report the tillage system and placement as well as residual and direct fertilization from 1995 used in their study, but two other papers did. Those through 1996. Two K and two P experiments were established on papers reported no yield increases from different P and farmers' fields with 10-yr histories of no tillage. An additional P K fertilizer placement methods under conventional-tillexperiment was conducted on one of Iowa State University's research age systems when soil test levels were high (Ham et al., farms. Treatments on farmers' fields included two rates of P (0 and1973; Rehm et al., 1988). However, at low soil test P 19.5 kg P ha Ϫ1 ) or K (0 and 51 kg K ha Ϫ1 ), placement of fertilizer levels, the largest response was from broadcast fertilizer. (surface broadcast or a subsurface band 5 cm beside and 5 cm belowEarly research in Iowa indicated banding of fertilizers the seed ) and time of fertilizer application. Treatments on the research was equal or superior to broadcasting fertilizers if confarm were similar, except the P fertilizer rates applied were 0, 19, 39,

Starter fertilizer can help improve early‐season corn (Zea mays L.) growth, especially under cool soil conditions, but corn hybrids may differ in their response to starter fertilizer. This study evaluated the response of corn hybrids to complete starter fertilizers applied under no‐tillage, dryland conditions. Nine site‐years of data were collected from 1993 through 1995 at four geographical locations: Doon (NW1) in extreme NW Iowa, Sutherland (NW2) in central NW Iowa, Lewis (SW), and Crawfordsville (SE). The soil types were as follows: NW1— Moody silty clay loam (fine‐silty, mixed, superactive, mesic Udic Haplustolls); SW—Marshall silty clay loam (fine‐silty, mixed, superactive, mesic Typic Hapludolls); SE—Nira silty clay loam (fine‐silty, mixed, superactive, mesic Oxyaquic Hapludolls); and NW2—Primghar silty clay loam (fine‐silty, mixed, superactive, mesic Aquic Hapludolls). Each hybrid was planted with and without starter fertilizer applied 2 in. to the side and 2 in. below the seed at planting. Hybrid‐by‐starter interactions were not significant for early‐season dry matter production, nutrient concentration, or grain yield in any of the site‐years, indicating that the hybrids, on average, responded similarly to starter fertilizer. Starter fertilizer increased early‐ season growth significantly in four of eight site‐years and grain yield in seven of nine site‐years. Average grain yield increases ranged from 4 bu/acre at the NW2 site in 1993 to 18 bu/acre at the SE site in 1995. Yield increases were not significant either year at the NW1 site. Increases in dry matter yield ranged from 18.7% at the SW site to 97.8% at the SE site in 1994. Starter fertilizer affected tissue K concentration to a much larger degree than it did N and P concentrations especially at the SE site. The results suggest that starter fertilizer will likely benefit no‐tillage corn for most hybrids in the northern corn belt even on soils with adequate P and K. Research Question No‐tillage systems have become attractive options for many corn producers because of potential on‐farm energy savings and the advantages of soil and water conservation. Residue cover on no‐tillage systems can result in cooler and wetter soils especially at time of planting. Cool soil temperatures can reduce early‐season growth, nutrient uptake, and yield of crops. However, starter fertilizers placed within the rooting zone of seedlings have been shown to improve early‐season corn growth and development due to better availability of the nutrients. Responses to starter fertilizers can vary among corn hybrids since they may differ in rooting characteristics, uptake and utilization of nutrients. The objective of this experiment was to evaluate the response of different corn hybrids to starter fertilizer in no‐tillage systems. Literature Summary Nitrogen and P are considered to be the essential ingredients in starter fertilizers. Some recent studies that have evaluated corn and grain sorghum response to N‐P starter fertilizers in no‐tillage environments, suggest hybrids res...

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Much of the corn (Zea mays L.) yield increases in the past five decades can be attributed to the identification and adjustment of controllable factors that limit production. This process must continue if we are to meet the food requirements of the future. The objectives of these experiments were to determine what combination of the producer controlled variables (e.g., N, P, and K fertilization, plant density, row spacing, hybrid, and timing of N application) would give maximum yields under the prevailing climatic conditions in the western Corn Belt. Eight field experiments were conducted in eastern and central Iowa from 1982 through 1984. Treatments varied with location but the treatment ranges were as follows: plant density—20 000 to 36 000 plants/acre; row spacing—20 and 30 in.; N rate—60 to 333 lb/acre; fertilizer P rate—0 to 99 lb/acre; fertilizer K rate—0 to 249 lb/acre; N timing—preplant vs. split (preplant and side dress); plus four different hybrids. Weather had a moderating effect on all but one experiment by either delaying planting or providing severe moisture stress. Mean experiment grain yields ranged from 103 to 178 bu/acre, with the combination of controlled variables giving maximum yields varying with site‐year. Grain yields did not respond to fertilizer N rates above the initial rate. Soil P levels were sufficient to produce maximum yields with or without added fertilizer P, and in 1983, added P resulted in a negative yield response. Grain yields responded to fertilizer K rates of 166 and 249 lb/acre in 1982 on plots with soil tests averaging 67 and 91 ppm K, respectively. The rate of 166 lb/acre resulted in grain yield increases in 1984 on plots with soil tests averaging 85 ppm K. The lowest plant densitities, which ranged from 20 000 to 26 000 plants/acre, gave maximum yields in all experiments. The row‐spacing variable resulted in a grain yield difference only in 1982 when 20‐in. rows showed an advantage over 30‐in. rows. Hybrid had a significant effect on yield in all but one experiment. These experiments demonstrate the increased risk to the producer who is striving for high yields but who cannot control or predict the weather.

The purpose of this quasi-experimental study was to determine if upper-level college students who participated in AgPAQ, an integrated course cluster learning community, would demonstrate enhanced learning in the areas of oral communication, written communication, and agronomic/economic technical content knowledge. The population (N = 182) consisted of students who participated in AgPAQ and five comparison groups: students in a farm management class; students in a stand-alone soil, fertilizer, and water management class; students in a soil, fertilizer, and water management class linked with an English course; and students in a paid volunteer group who had not previously participated in AgPAQ. Instruments included three rubrics that measured performance on written communication, oral communication, and agronomic/economic technical content knowledge. Analyses revealed that AgPAQ participants scored higher than non-AgPAQ participants on measures of oral and written communication in all comparisons. Also, AgPAQ participants scored higher on measures of agronomic/economic technical content knowledge than students in the non-AgPAQ paid volunteer group and students in the stand-alone soil, fertilizer, and water management class. AgPAQ participants also scored higher, but not significantly higher, than students in an English and agronomy linked integration. AgPAQ fostered enhanced learning in oral communication, written communication, and agronomic/economic technical content knowledge.