Detailed data are needed to quantify the effect of conservation tillage (CT) on corn (Zea mays L.) emergence and early growth in the Northern Corn Belt. Corn was grown using three CT systems: till‐plant (TP), chisel (CH), and no‐till (NT) and conventional moldboard plow (CN) on a Griswold silt loam soil (Typic Argiudoll) during the 1982 to 1984 growing seasons. Soil temperature at the seed depth (5 cm) was measured hourly. Daily means and cumulative growing degree days (GDD) based on seed zone temperatures were calculated. Corn emergence was monitored. Leaf area and dry matter per hectare were measured at different growth stages. Relative growth rates (RGR) were calculated from daily measured plant heights. Soil temperature at the 5‐cm depth ranked CN > TP > CH > NT. Initial corn emergence rates with the NT system were depressed compared to CN; the emergence rate ranked CN > TP = CH > NT. However, time to 100% emergence was delayed by 8, 2 to 3, and 2 d for NT compared to CN in 1982, 1983, and 1984, respectively. All tillage systems started to emerge at 40 to 55 GDD and reached a maximum emergence at 70 to 80 GDD. During the first 5 weeks after emergence, corn growth parameters (plant height, leaf area, dry matter) of NT were consistently lower, and in some cases significantly lower than CN. These growth parameters were highly correlated with GDD. The RGR fluctuated in the same manner as the daily 5‐cm soil temperature during the first 5 weeks after emergence. The correlation coefficients of log RGR vs. daily mean soil temperatures were highly significant and followed the soil temperature trends. Thus, the lower soil temperature associated with CT systems, especially NT, is one of the main factors affecting emergence and seedling growth and development.

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This study was conducted to provide needed data comparing corn (Zea mays L.) growth and productivity for several conservation tillage (CT) systems. Such data will provide necessary information to better evaluate the economical potential of CT systems in the Northern Corn Belt. The tillage systems used in this study were till-plant (TP), chisel (CH), no-till (NT), and conventional (CN) tillage. The study was conducted on a Griswold silt loam soil (fine-loam, mixed, mesic Typic Argiudoll) at Arlington, WI, and a Plainfield loamy sand soil (sandy, mixed, mesic Typic Udipsamment) at Hancock, WI, over a 3-yr period. Final plant emergence and growth and yield parameters were measured. The final plant emergence was higher with the CT systems compared to CN at Arlington, while the final plant emergence of the NT system was lower than other tillage systems at Hancock. Plant height, leaf area, and dry matter per plant early in the growing season, for both locations ranked: CN > TP ~ CH > NT, and in most cases were significantly different. However, at the end of the growing season, these growth parameters were not significantly different. Days from planting to 50% silking for the NT system were significantly delayed by 2 to 3 and 4 days at Arlington and Hancock, respectively. No-till had the highest grain moisture content. Grain yields with CT systems were equal to or greater than CN tillage at both locations. No-till grain yield at Hancock was 18% greater than CN when rainfall was below normal in 1983. Threeyear grain yield averages for the silt loam soil were 8. 75, 8.78, 8.97, and 8.49 Mg ha 1 for CN, TP, CH, and NT, respectively. Threeyear grain yield averages for the loamy sand soil were 6.48, 6.48, 6.44, and 6.79 Mg ha 1 for CN, TP, CH, and NT, respectively. The results from this study showed no serious growth and yield reductions with CT systems compared to CN tillage in the Northern Corn Belt.

A laboratory sprinkler (rain) infiltration experiment was carried out on long stratified columns of sandy soil (Typic Torripsamments) packed to 1.50 g cm -3 bulk density to investigate the effect of gel-forming conditioner (Jalma) on wetting front advance Z, water distribution, and redistribution profiles under different sprinkler intensities I using a simple sprinkler simulator. Five concentrations of Jalma J, 0.0, 0.25, 0.50, 0.75, and 1.0% (on dry weight basis), were uniformly applied to the upper layer (10-cm depth) at three sprinkler intensities of 1.25, 2.25, and 3.25 cm h -1 . The time required for the wetting front to reach 10-cm depth t° was significantly increased either by increasing J added to the upper layer or decreasing I applied on soil surface. However, the treatment of 1% J caused surface ponding before Z had advanced to 10-cm depth for the three values of I. A fairly uniform water profile was produced in the homogeneous soil (J = 0%), and the constant water content as fractional volume θ T was found equal to the ratio of the sprinkler intensity I to the velocity of the wetting front v. Addition of Jalma to the upper layer increased the water content in that layer, which was magnified by increasing I, but did not affect the value of θ T in the untreated lower layer. The higher water content observed at the soil surface due to Jalma application never approached the corresponding value of the saturation water content θ s under sprinkler infiltration. The experimental results revealed that the water movement in the untreated lower layer was unaffected by Jalma applied to the treated upper layer. Equations based on Darcy's law along with the physical properties of the resulted water distribution profile were derived to compute Z and θ T under sprinkler infiltration as affected by Jalma applied to the upper layer of sandy soil. The development of water redistribution profiles indicated that the amount of water retained in the treated upper layer was much higher than that in the untreated upper and lower layers at the same corresponding redistribution times and sprinkler intensity. However, the same uniform water content θ T , which was associated with -10 kPa matric potential on average, was approximately achieved in the untreated lower layer 3 days after sprinkler infiltration regardless of Jalma applied to the treated upper layer. In Address correspondence to A. M. Al-Omran. 217218 Y. Z. El-Shafei et al. general, the study may suggest application of Jalma conditioner at 0.75% to the upper layer (10-cm depth) of sandy soil under medium sprinkler intensity I around 2 cm h -1 and a wetted depth not more than 20 cm for the benefit of water use efficiency.

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