The primary purpose of this research is to determine if there are any crop growth differences, including yield, between the three management systems at the Ohio MSEA. In order to quantify crop growth, the plants are divided into several components and these components are tested for differences in growth between the management systems. In addition, weed growth in each management system is tracked throughout the season. In the event that crop growth differences are detected, these data can be analyzed to determine if differences in weed competition could account for the differences in crop growth.
Management practices which reduce potential environmental impacts will only be adopted by farmers if there are no associated reductions in productivity. If the management practices being evaluated at the Ohio MSEA do result in productivity differences, it is essential that this is documented in sufficient detail to establish the probable cause. This specific research activity quantifies crop growth, including yield, to determine if the management systems differ in productivity due to reduced chemical inputs.
The yield and crop growth data from 1991 and 1992 corn phases suggest that there is no conclusive evidence that one management practice will result in less yield than the others. The corn phase of the corn/soybean/wheat-vetch rotation did have the lowest mean yield both years, but there was enough variation in yield among replications that there was no statistical significance to the difference in yields. Soybeans grown on ridges yielded less than conventional soybeans in 1991; a dry year. In 1992 there was no difference in yield between the two treatments. No evidence of significant differences in weed growth has been recorded, even though some treatments received reduced herbicide rates.
Three management systems are under intensive study at the Ohio MSEA. A summary of the corn and soybean phases of the three systems is presented in Table 1. The continuous corn system (c/c) is chisel plowed, the corn/soybean rotation (c/s) is chisel plowed before the soybeans, and no tillage is done before the corn is planted. The corn/soybean/wheat-vetch system (c/s/w-v) is ridge-tillage.
Each of the three cropping systems was replicated three times in 0.4 ha plots, arranged in a randomized complete block design, so that each phase of each rotation was present every year. Beginning at crop emergence, a 1 m strip of row crop or quadrant for vetch, wheat, and weeds samples was removed every two to four weeks. The sample wet biomass was recorded, then the plants (corn and soybeans) were separated into leaves, stems, and seed: oven-dried overnight, then re-weighed, Wheat, vetch and weeds were dried whole and weighed. Yields were determined by weighing the grain harvested from the entire plot, and adjusting for grain water content.
In 1991, the continuous corn treatment yields ranges from 5,784 to 8,991 kg/ha (92 to 143 bu/ac), with a mean yield of 7,815 kg/ha (124.2 bu/ac); the corn/soybean rotation corn yields ranged from 6,539 to 8,299 kg/ha (104 to 132 bu/ac) with a mean yield of 7,293 kg/ha (116 bu/ac); and the corn/soybean/wheat-vetch treatment yielded 6,162 to 6,224 kg/ha (98 to 99 bu/ac) with a mean yield of 6,206 kg/ha (98.7 bu/ac). There was no statistical evidence that the difference in corn yields was due to the management practices in 1991, even though the planting dates differed among treatments by 7 to 12 days, and the nitrogen inputs for the ridge-till system were less than half that of the other two treatments.
The first two corn biomass sampling events (May 30 and June 24, 1991) showed statistically significant differences in plant biomass between treatments, most likely due to the different planting dates. By August 5, 1991, the corn biomass measurements between the three treatments were no longer different. The end-of-season weed biomass (sampled September 24, 1991) was not significantly different between treatments, indicating that the three management systems had similar weed control. The herbicide applications are shown in Table 1.
The 1992 continuous corn yield ranges from 10,122 to 10,940 kg/ha (161 to 174 bu/ac) with a mean yield of 10,531 kg/ha (167.5 bu/ha). The 1992 corn/soybean rotation corn yield ranged from 11,000 to 11,191 kg/ha (175 to 178 bu/ha) with a mean yield of 11,106 kg/ha (177 kg/ha). The corn/soybean/wheat-vetch rotation corn yields ranges from 9,997 to 10,185 kg/ha (159 to 162 bu/ac) with a mean yield of 10,081 kg/ha (160 bu/ac). There was no statistical evidence that the difference in corn yields was due to the management practices in 1992, even though the corn phase of the c/s treatment was planted 5 days prior to the corn continuous corn, and 9 days prior to the corn phase of the c/s/w-v treatment. The continuous corn and c/s treatment received more nitrogen than the c/s/w-v corn. Also, the c/s/w-v treatment received 1/9th the herbicide per ha as the other two systems. The weed pressure 25 days after planting and before cultivation in the ridge-till system was statistically different from the other two treatments (3.6 g/m2 for the c/s/w-v corn vs 0.24 and 0.08 g/m2 for the c/s and c/c corn respectively). The first mechanical cultivation occurred 26 days after planting and weed sampling performed 54 days after planting showed that the weed biomass differences were no longer statistically difference, nor were the end-of-season weed biomass measurements.
The 1991 soybean yield differences were statistically related to management practice. The c/s/w-v soybeans grown on ridges, yielded an average of 2,425 kg/ha (36 bu/ac) and the soybeans grown on flat ground (c/s soybeans) yielded an average of 3,564 kg/ha (53 bu/ac). There were significant differences in plant biomass throughout the season. The average end-of-season biomass differences were not statistically attributable to management practice however.
Soybean yields did not show a treatment difference in 1992 (the average yield was 3,156 kg/ha (47 bu/ac)), and no significant differences in biomass were observed after planting data differences had been overcome. Early weed growth was not different between treatments, however just prior to harvest, the weed biomass in the c/s soybean plots was 60.8 g/cm2 vs. 3.9 g/cm2 in the c/s/w-v soybeans. The majority of the weed in the c/s soybean plots were cocklebur. It is interesting to note that the plots which received more herbicide had more weeds at the end of the season.
Harvest loss was recorded for both treatments of soybeans in 1991 and 1992. The number of soybeans passing out the rear of the combine did not differ by treatment, but the number of soybeans missed by the header was higher for the ridge-till treatment in 1992, but not in 1991.
Wheat was successfully grown on ridges in 1991 and 1992. In 1991, the wheat yielded 1,962 kg/ha (44 bu/ac) at a seeding rate of 135 kg/ha (2 bu/ac). The yield in 1992 was slightly less (2,425 kg/ha or 36 bu/ac) at a seeding rate of 67 kg/ha (1 bu/ac). No nitrogen was applied to the wheat in either year.