ISSUE 8  June 22, 2000

NODULES NOW FORMING

    Alfalfa, soybean, dry edible beans, field peas and lentil are important legume crops in North Dakota. The combined acreage of these crops any year will exceed 3 million acres.

    Nodulation is one of our better diagnostic tools for gauging relative crop conditions. Legumes in stress will have limited nodule numbers. Severe stress after nodulation can cause nodule sloughing. Stress can be from several sources. However, drought and nutritional deficiencies are most common. Wet saturated soils also can reduce or eliminate nodule formation.

    Legumes depend on nodule growth for their nitrogen supply. Hence, stress and reduced nodulation can mean a nitrogen shortage before the crop matures. This can be seen each year somewhere in North Dakota dry bean and soybean crops. It’s rare we mature these crops without moisture stress. Drought and nutrient stress have the same affect, lower yields and early harvest.

    Nodules develop on tender tissue of hair roots rather than corky tissue of older roots. As a result, they can be found within two weeks after seedlings emerge. They will occur as clusters centered at the seeding depth when seed is inoculated and sparsely on the rest of the plant root system from indigenous Rhizobium present in the root mass. Active nodules, those producing nitrogen for the crop, will have a pink to rusty red interior. Inactive nodules will be white to green in color within the nodule.

UNEVEN SUNFLOWER SPACINGS

    Poor seedbed conditions have resulted in uneven stands of sunflower. Plants too far apart, too close together and different sizes are common in fields of adequate average population. Unevenness is assumed to be undesirable, but the lack of response to increased uniformity from close row spacing suggests that moderately uneven stands of sunflower may not affect yield. The effects of uniform and nonuniform plant
spacings within an overall population of 20,000 plants per acres in rows 30 inches apart were studied at five locations over two years in Minnesota.

    The distributions tested included uniformly spaced, clumped, and widely spaced plants: a) uniform single - plants 10.5 inches apart, b) uniform double - two plant groups 21 inches apart, c) 5-5-5 - five plants 5.25 inches apart, 31.5 - inch space, etc., d) 7-1-7 - seven plants 3.5 inches apart, 31.5 - inch space, one plant, 31.5 - inch space, seven plants 3.5 inches apart, 31.5-inch space, one plant, etc.

    The uniform, single-plant spacing gave the highest average yield. Both oilseed and nonoilseed hybrids responded the same to the plant distributions.

 Sunflower yields at five locations in Minnesota

    Plants uniformly spaced in pairs did not support each other; they lodged more and yielded less than uniformly spaced, single plants. Paired plants may give more emergence through crusted soil than single plants, but this possibility was not evaluated.

    Head moisture differences among plant distributions were highly significant on the average. Plants spaced singly and uniformly had lower head moisture percentages than did the 7-1-7 arrangement in all trials.

    The nonuniform plant distributions were uneven in height from preheading to maturity. The center plants of the groups of five and seven plants were 4 to 7 inches taller than the single plants. Average plant heights among the distributions did not differ noticeably.

    Plant distribution did not, on the average, significantly affect test weight per bushel of seed.

FIELD DAYS: DATES AND STARTING TIMES

Field days showcase the latest research being carried out by scientists with the North Dakota Agricultural Experiment Station and the NDSU Extension Service. Each station has various tours planned. 

MTD = Mountain Daylight Time

Duane R. Berglund
Extension Agronomist
dberglun@ndsuest.nodak.edu

FLOODING ON WHEAT AND BARLEY

    What impact recent heavy flooding is having on crops is a question I believe many have, without phone service there maybe other concerns. I have attempted to assemble a little information on the impact of the recent flooding. Most information in the literature is relative to water logging and not flooding.

    The first major impact of soil completely covered with water is a rapid depletion of oxygen required for plant growth and development. The other major impact of flooding is change in nutrient status either by leaching or changing their availability to the plant. The response to flooding will vary with duration, and temperature.

    Obviously the longer the duration of the flooding the greater the injury. The injury results from plants inability to grow in an anaerobic environment. While specific information on how long small grains can survive under water has not been widely reported, most indications are that wheat can withstand water logged soils for up to 24 hours with out excessive damage, barley is less that this. Depending on the conditions wheat can probably survive saturated conditions for up to two days. Conditions that influence this are temperature and stage of growth. Under cool conditions metabolic activity is less than at warm temperatures and the demand for oxygen is less. A younger crop has a smaller demand for oxygen and may be able to survive
better. Even so, a small grain crop that is submerged in water for two days, or longer, has little chance for survival.

    Flooding of water intolerant crops generally disrupts normal transpiration and water adsorption. Stomata in affected plants will close and can remain closed for long periods, the duration is affected by soil water conditions following the flooding. The net effect is reduced respiration, transpiration, and photosynthesis. When a small grain crop does survive flooding, recovery maybe very slow and yield will be dramatically impacted.

HAIL INJURY

    Limited hail fell in some areas this week also. Two articles were included in last weeks pest report for small grains broad leaf crops.

    Even though our phone and Email will be down for about three weeks the U.S. Postal Service will still deliver and we will respond.

Michael Peel
Small Grains Extension Agronomist