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| Pennsylvania Association for Sustainable Agriculture |  |
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Tim and Anne Bock - Wills Daal Farm - Kutztown, PA (2004) 
Experimenting with Weed Control in Small Grains Wills Daal Farm, the home of PASA members Tim and Ann Bock, near Kutztown, PA was the site of on on-farm evaluation of weed control in spring oats during 2004. The farm consists of approximately 160 acres of certified organic cropland, most of which is planted in field crops with a small but increasing acreage of mixed vegetables. The Bocks are advocates of lengthy crop rotations to prevent the build-up of pests and to enable them to manage fertility of their fields. Field crops usually found on the farm include small grains (wheat, oats, and occasionally spelt and barley), soybean, corn, hay crops, and cover crops (rye and hairy vetch). While weed management can be a challenge in any crop, it can be especially difficult in small grains, due to an inability to use in-row cultivation. High seeding rates and optimum planting dates can promote quick establishment of the crop to create a competitive environment with the weeds. Broadcast cultivation of drilled crops is another option to control weeds, which is also receiving attention. The research trial was designed to compare weed control and oat grain yields after single, double or triple cultivations with a flexible tine weeder. The idea of using a flexible tine weeder in small grain production stemmed from positive observations in other research trials. We were all interested if the number tine weedings would decrease weed populations and increase oat yields. A 3-acre field was used for this research trial. In March, cattle manure was spread on the field that was previously in soybeans. In early April the field was moldboard plowed, field cultivated, and spring oats were drilled. The treatments consisted of three intensities of flexible tine weeding: one, two, or three weedings over a ten-day period beginning immediately after oats were drilled. Each treatment was replicated four times in a randomized complete block experiment. The twelve research plots (measuring approx. 15 ft. wide and 560-620 ft. long) were drilled with "Blaze" oats at 4.5 bushels per acre on April 16. In this study, a 15 ft. wide Lely flexible tine weeder was used. Flexible tine weeders are designed to disturb the root zones of weed seedlings while they are in the very delicate "white thread root" stage, which often results in seedling desiccation and death. The first tine weeding occurred on April 19 prior to emergence of any oats. The weeder was adjusted to penetrate to about one inch below the surface. This operating depth was decreased slightly to limit oat disturbance during the second (April 25) and third (April 30) weedings. Damage to the oats during the second and third cultivations did increase as the oats grew in height. On May 25, weed and oat densities were surveyed and on July 28, three days prior to combine harvest of the research plots, aboveground plant biomass was clipped, hand-separated (weeds versus oats), dried, and weighed. Combine-harvested grain yields and moisture content were collected from a 13-foot wide swath centered in each plot. Very few weeds were beginning to germinate during the period when the flexible tine weedings took place. Also there was significant visual damage to the oats, which were 3 to 4 inches tall, when the third weeding was conducted on that treatment. There were no differences between treatments (one, two or three cultivations with the tine weeder) for weed density (giant foxtail, common ragweed, Pennsylvania smartweed, and Virginia copperleaf) or oats when counted in May. Likewise when total plant biomass was sampled at oat maturity and separated into weed fractions and oats, and when grain yields through the combine were analyzed, no differences were observed between the weeding frequency treatments (see figure 1 for combine harvested oat yields). Visual comparisons with adjacent non-weeded parts of the field indicated similar weed species and densities. The greatest reason for lack of control of weeds in this experiment was that the weed species present in this field were not germinating when weeding occurred. The summer annual weed species in this seed bank normally germinate later than when spring oats are planted. Even when tine weeding or other tillage operations coincide with weed seed germination, an additional factor that can affect the weed control potential of flexible tine weeders is the number and size of soil crumbs and clods. Spring and summer 2004 were wetter than normal which resulted in the production of larger soil crumbs and clods during pre-plant tillage operations. The surface clod problem was worsened when the tine weeder caught already formed clods and "rolled" them onto the surface. These soil surface conditions do not contribute to ideal weeder disruption of small weed seedlings. The larger soil clods, left unbroken, can be an ideal environment for weed germination and establishment as the rooting environment is protected from disruption and desiccation. This study did not demonstrate a weed control benefit from using a flexible tine weeder in spring oats. However, a surprising outcome of the study was that grain yields were not negatively impacted by later tine weedings when oat shoot lengths were approaching 4 inches. Many clods were rolled onto shoots, but the oats were able to compensate and yield as well as those plots weeded only once, prior to oat emergence. For a future investigation, we are considering fall-planted winter small grains, which may be better suited to benefit from the flexible tine weeder. Winter annual weeds (mustards, chickweed, henbit, etc.) germinate during the time when farmers are planting the crop. More closely matching schedules of crop planting and weed germination should enable farmers to use weeders for management of some of weed species.
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