Considerations In Preharvest Weed Control

An excellent opportunity for weed burn down, perennial weed control and harvest aid is through preharvest herbicide application. However, following are some factors to consider before applying a herbicide as a harvest aid:

 The expectations for preharvest weed control usually exceed reality -- it is not possible to kill or dry down a three-foot weed in the same manner as a three-inch weed. Lower portions of the weed may not be affected.

 It requires time to dry down treated weeds -- usually 7-10 days. It may require more time if wet and/or cool weather conditions occur after treatment. All herbicides labeled for preharvest application are systemic and slow acting which requires a longer dry down period as compared to contact, fast acting herbicides.

 The intent of a preharvest treatment should be to facilitate harvest and reduce harvest loss. Preharvest treatments do not decrease yield losses due to weed competition or prevent weed seed production.

 Herbicide drift from preharvest treatments can cause major problems this time of year. Consider sensitive crops (sugarbeets, potatoes, etc.) and other plants (trees, gardens, etc.) in the general vicinity of the field receiving treatment.

See product options and treatment recommendations under Sections B24-B29 of the 2003 NDSU Weed Control Guide online: www.ag.ndsu.nodak.edu/weeds/w253/w253w.htm .

— Richard Zollinger, NDSU extension weed specialist

Counting Kernels to Measure Harvest Loss

Kernels or seeds per pound, bushel, cwt, and number per square foot to equal one unit loss per acre at harvest

Crop No. per pound*   to equal  per 1 bushel unit loss/A No per square foot Spring Wheat 14,300 20 Durum Wheat 11,500 16 Barley 13,500 15 Oats 15,500 11 Flax 88,000 113 Rye 18,000 42 Soybeans (small) 3,300 4 Soybeans (large) 2,400 4 Corn (medium grade) 1,500 2 Sunflower (oil) 9,000 5 Sunflower (conf.) 5,000 2.5 Navy Beans 2,500 4 Pinto Beans 1,250 2 Sorghum 15,000 18 Sudangrass 44,000 40 Proso Millet 80,000 84 Foxtail Millet 220,000 242 Buckwheat 15,000 16 * These are average numbers from past seasons, and individual varieties or hybrids will vary among themselves as well as be influenced by environmental factors. Source: NDSU

Proper End-Gate Grain Sampling

To collect a representative sample from a stream of grain flowing from a truckbox end-gate, certain requirements must be met:

1. The material should fall free from the end-gate for about 1 foot.

2. The entire stream of grain (side to side and front to back) must be cut as the sample passes through the stream.

3. The sampling device must not be allowed to completely fill with grain before it leaves the grain stream. If it does, some of the flowing grain will pass around the sampler and not be sampled.

4. Collect a sample from each 500 bushels with a minimum of two cuts per truckload. A cut is a single pass of the sampling tool through the grain stream. Any sampling tool can be used to collect the sample as long as the above requirements can be met.

– NDSU Extension Service