NDSU Crop and Pest Report

Plant Science

ISSUE 5   June 3 2004


The wet and cool weather of the last few weeks has delayed planting in many counties, particularly in the northwest and north-central regions of the state. We are currently well beyond the optimum time period (April 15 to May 15) for planting small grains for maximum yield. Small grain yield in most years is reduced by 1 to 1.5% for each day that planting is delayed beyond May 15. Last year, because of the unusually hot weather in June and dry conditions in July, yield penalties associated with late planting were even higher. I have had numerous questions about what varieties are best adapted to late plantings. I am not aware of any recent data comparing the performance of the most commonly grown varieties when planted late. Nevertheless, the following points should be considered if you are still planning on planting a small grain crop this spring:

Joel Ransom
NDSU Extension Agronomist - Cereal Crops



The objective of rolling soybean ground is to push rocks down to the soil surface and level the soil to allow a low combine cutter bar height during harvest. This will reduce harvest loss by cutting soybean stems below pods instead of cutting above or through low pods and leaving beans in the field. Soybean fields are rolled after planting, either pre- or post-emergence. The advantage with rolling before the crop has emerged is improved seed-to-soil contact and reduced potential for plant injury. Disadvantages are increased potential for soil surface crusting and soil erosion. Rolling fields after the crop has emerged likely will cause plant injury such as cracked or broken stems. Plants will die if the stem is broken below the cotyledon leaves, due to loss of all growing points. Injured plants may be more susceptible to lodging and disease. Limited university research and farmer testimony indicates that rolling between the cotyledon and 1st trifoliate stages of soybean may limit injury potential. Also, roll during the warmest part of the day on less turgid plants to minimize injury potential. Late afternoon would be much better than rolling emerged soybeans in the morning hours.

A rolling soybean ground trial at NDSU Carrington R/E Center in 2001 indicated a trend of plant population decline as rolling was delayed from PRE to the second trifoliate stage. However, seed yield was similar among the unrolled check and all rolling treatments. A similar trial was conducted in 2003 at Carrington and reported by Greg Endres, Extension Area Agronomist and Bob Henson, Research Agronomist.

The soybean variety, RG200RR was solid-seeded (7-inch rows) on May 27. A 3000 lb, 15-ft wide, 18-inch diameter, 3-point hitch mounted Bison roller was used for field rolling during afternoons on a dry soil surface preemergence and during early emergence, cotyledon, and first trifoliate soybean growth stages.

Table. Soybean impact with timing of field rolling, Carrington, 2003.

Plant stage

Soybean stand
1-2 WAT**

Plant injury*
1-2 WAT

Seed Yield













#50% cotyledons emerged








1st trifoliate








C.V. %




LSD 0.05




* Injury included bent, broken, or calloused stems.
** Weeks after treatment

Soybean plant injury increased as post-emergence rolling was delayed. Soybean stand, lodging, and yield were generally similar to the untreated check. Plant moisture status (time of day, soil moisture content), location of plants in ridges/furrows, presence of surface residue, speed of rolling, and other factors may also influence plant tolerance to rolling.



Cold weather, frost and cool soils have resulted in less than desired plant stands in some fields this season. Even through a lot of crops were planted early, the decision to replant is always a difficult one. The decision of whether to replant a row crop with a reduced stand is a function of the calendar date plus the stand that is available. Frost, wind, cold soils and some cutworm activity have all taken their toll in reduction of row crop stands.

Reduction in stand is the major factor in deciding to replant row crops and certain oilseeds. As we move later into June, the decision of how much stand to keep changes, because if we tear up the field and reseed, the late plantings have much less yield potential and the risk of late season frost injury increases.

With corn, around June 10, with stands of less than 12,000 plants per acre, we probably would want to tear it up and replant to a crop like sunflower or soybeans that can be planted at this date and still mature. By June 15, the decision may be to keep a stand of 12,000 to 14,000 plants per acre because it is too late to plant a good alternative.

Uniformity of stand is the key to evaluating a poor stand. If there are no large skips in the field, fairly low plant populations of soybeans (75,000A), dry beans (50,000/A) and sunflower (10,000 to 11,000/A) can still maintain yields. These plants have the ability to branch or flex and fill in space. This is not as true with corn and weeds also become a bigger problem.

With 50 percent a stand of soybean, dry bean or sunflower, you may want to leave them. If less, you may want to replant to an earlier variety or switch to another crop. About the only choice in the mid- June is flax, buckwheat, early-short season sunflower or proso millet. Also, one must take into consideration the herbicide used in the prior planted crop and will it create a problem with injury to a crop change.

Duane Berglund
NDSU Extension Agronomist

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