Legume winter ground covers may contribute to row crop systems by providing protection from wind and precipitation and by releasing N to the subsequent row crop, but to attain effective size, these legumes must begin growth well before the winter. A 3‐yr study was conducted to evaluate the performance of four commonly used forage legumes interseeded into corn (Zea mays L.). Alfalfa (Medicago sativa L.), yellow sweetclover (Melilotus officinalis Lam.), red clover (Trifolium pratense L.), and alsike clover (T. hybridum L.) were seeded in a mix consisting of equal seed numbers (pure live seed) from each species. Seeding dates were (i) at corn planting and (ii) at last cultivation. Control treatments were nonseeded. Two levels of weed control also were evaluated. In addition to the factorial experiment, the four species were seeded separately in other corn plots. The herbicide EPTC was also evaluated for use in interseeding. In drier than normal seasons (summer of 1984 and spring of 1985), soil moisture was significantly depleted under interseedings; this depletion was not observed in seasons of normal precipitation. Legume stands and ground cover reflected moisture and light conditions during establishment. In the 2 yr that rows were oriented east‐and‐west, stands conformed to a skewed modal distribution across the inter‐row. Alfalfa and sweetclover usually were better established and produced more cover than either red or alsike clover. Corn yields were not significantly reduced by interseeding per se, but they were reduced when interseeding at the early date interrupted weed control. In treatments that used the herbicide, corn yields were greater than where herbicide was not used, but yields were still significantly below those of the nonseeded control. Research Question Row crop producers around the USA are examining methods of protecting the soil between harvest and planting, and winter cover crops are one alternative receiving interest. Cover crops, by sequestering soil N, also reduce leaching of N below the rooting zone, and legume covers can fix additional N that may be used by row crops in the rotation. Farmers considering the practice need to know: appropriate cover crop species for their area; the most economical and effective methods for establishing the cover crop; and how to manage the cover crop to avoid competition with the row crop. This project was designed to answer those questions relative to use of forage legumes as cover crops following corn under mid western conditions. Literature Summary Research on cover crops in corn has often found that practices that favored cover crops (e.g., wide rows, earlier seeding dates) decreased corn yield. Corn yield can also be decreased by competition from weeds associated with cover cropping. While weed control is a real issue, weed effects on the row crop should be understood as a question separate from effects of the cover crop itself. Study Description The study was conducted over 3 yr on a farm in central Iowa. Soils were loam, clay loam, and silty clay loa...

Strip intercropping seeks to capture the biological efficiency of intercropping in traditional agricultural systems and is compatible with agricultural equipment used in the U.S. This efficiency stems from complementary use of resources by constituent crops and is a function of crop selection, strip width and orientation, weed control, and other factors. Strip intercropping requires a high level of management; further, some reports suggest the gains and losses more-or-less balance in actual production situations. These questions are best addressed by the performance of strip intercropping as implemented by farmers in production situations. Practical Farmers of Iowa (PFI) members have worked with Iowa State University agronomists to evaluate strip intercropping. For three years six farmers compared strip intercropping to field blocks of individual crops. The strip intercrop systems employed three crops: corn, soybeans, and small grains with a forage legume underseeding. The comparison systems, crops grown in sole-crop blocks, consisted of the same three crops on four farms (planting pattern comparison) or, on two farms, just corn and soybeans in rotation (systems comparison). Yields and field operations were recorded and entered in the Iowa State University Crop EnterpriseRecord System (CER) to derive gross profit, total production cost, and net profit for each crop component and for each cropping system on every farm. Strip intercropping net profit was generally greater than that infield blocks, and intercropping compared favorably with CER results obtained from corn-soybean rotations on other farms around Iowa. Land equivalent ratios (LER) were usually greater than 1.0, indicating satisfactory biological efficiency. Despite occasional problems, in this set of 18 site-years strip intercropping was associated with greater stability of net profit.

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The weed management system of most producers is complex and represents the summation of years of experience and informal observation. The ridge tillage, row crop system described here is especially complex because it seeks to use cultural and mechanical weed controls in preference to herbicides. Both experience and formal experimentation have contributed to the development of the system. Fundamental are two working hypotheses that may appear counterintuitive: (i) that tillage can stimulate weeds and (ii) that weeds can be used to control other weeds. Results of on‐farm trials on the Thompson farm have supported these hypotheses. Additional on‐farm trials have pointed toward conditions in which rotary hoe tillage can be used to best effect to eliminate weeds. Results of 51 replicated on‐farm trials by Practical Farmers of Iowa (PFI), an organization that generates and shares information about profitable, environmentally sound farming methods, showed that ridge tillage without herbicides is an effective and economical system for weed management and row crop production. Experience gained developing this alternative weed management system can be summarized in guidelines applying, respectively, to the overall system, the planter, the rotary hoe, first cultivation, and second (lay‐by) cultivation. Research Question Can weeds be effectively managed in a row crop system that relies primarily on cultural and mechanical techniques? Moreover, would such a weed management system be economical and could it be compatible with cover crops and residue management practices that reduce soil erosion? Literature Summary Observation: Farmers who do not use primary tillage frequently see a great increase in weeds where endrows are disked. Research has shown that ridge tillage avoids this kind of soil disruption and the stimulatory effect it has on some weeds. Ridge‐till also mechanically displaces weed seeds from the row at planting. Observation: Highway widening exposed soil along several fields; the ditches taken out of fields where herbicides had been used and only row crops were raised grew a solid stand of velvetleaf. The ditches from fields in a corn‐soybean‐corn‐oatkay‐hay rotation, where herbicides had not been used for the previous 18 yr did not have velvetleaf. While the crop rotation difference may have affected the weed seed bank in the two kinds of fields, crop history showed a seed reserve in both. Research has shown that plants can have chemically mediated suppressive effects on other plants, the phenomenon termed allelopathy. Could allelopathy be responsible for the observed difference in velvetleaf along the road cut? Study Description Observation and experimentation have led to an alternative weed management system in which herbicides have not been used for 18 yr. Important elements of the system are: ridge tillage, the rotary hoe, a weed suppressive and allelopathic cover crop of rye drilled just on the ridge, and a diverse crop rotation to break weed cycles. Replicated on‐farm experiments have contributed to the ev...