Analysis of the effect of two tillage systems on soybean (Glycine max (L.) Merrill) growth

The majority of the existing literature suggests that on highly-drained, well structured soils of the Corn Belt, soybean yield is not substantially affected by tillage. Available reports of differences are in the minority. There is relatively little information as to what extent and under what conditions the tillage methods affect the growth of soybean in the central Corn Belt. This is of particular interest since soybean grown with no-till conditions often appear smaller and less vigorous than soybean grown with conventional tillage methods with no-yield loss. To investigate the effects of tillage on soybean growth, a 2-year field study was conducted at Urbana, Illinois on a long-term tillage experiment involving a corn-soybean rotation. The two tillage methods selected far the study were: (1) conventional tillage (CT) consisting of fall moldboard plowing (20-25 cm deep) of corn followed by spring disking (7.5-10 cm deep) and field cultivating and (2) no-tillage (NT). An indeterminate soybean cultivar (Williams-82) was planted in May of each year at a rate of 33 seeds m{dollar}sp{lcub}-1{rcub}{dollar} on a Thorp/Cullo silt loam soil (fine-silt, mixed, mesic Argiaquic Argialbolls) with 2.4-3.1% organic matter and a pH of 6.7. Lasso (alachlor) and Sencor (metribuzin (4-amino-6-(1,1-dimethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one)) (pre-emergence herbicides) were used for weed control at rates 3.365 kg ha{dollar}sp{lcub}-1{rcub}{dollar} and 0.630 kg ha{dollar}sp{lcub}-1{rcub}{dollar} respectively. Prior to planting, NT plots were sprayed with glyphosate (N-(phosphonomethyl) glycine) (post-emergence) at 0.840 kg ha{dollar}sp{lcub}-1{rcub}{dollar}, and 2,4-D (2,4-dichlorophenoxy) acetic acid) at 0.467 kg ha{dollar}sp{lcub}-1{rcub}{dollar} plus X-77 crop oil concentrate at 0.5% v/v with water at 187 L ha{dollar}sp{lcub}-1{rcub}.{dollar} Soybean yield was not affected by either tillage or the interaction between year and tillage. Soybean growth parameters were affected by the tillage system and the year. The total plant dry biomass (TPDB), the stem dry biomass (SDB), the leaf dry biomass (LDB) and the pod dry biomass (PODDB) were substantially larger with CT than with NT. The soybean planted with CT demonstrated hastened maturity, increased crop growth rate (CGR), leaf area index (LAI), net assimilation rate (NAR), leaf rate ratio (LWR) and specific leaf area (SLA) compared to soybean grown with NT.