ISSUE 11   July 23, 2009

LODGING IN SMALL GRAINS

In many parts of the state, the small grain crop has good to excellent yield potential this year. With the growing weight of the spikes as the crop matures, lodging can become problematic especially as we get wind combined with rain.

Lodging is the term used to describe a crop when its stems have partially or completely fallen over from their normal near vertical orientation. Root lodging, the most common type of lodging, occurs at the base of the plant when roots fail to anchor it properly. Stem lodging can occur at any location on the stem and tends to be most common later in the season as plants mature and stems become brittle. When root lodging occurs early it is possible for some stems to partially erect themselves. This is accomplished by the plant bending at one of its nodes. These nodes tend to enlarge and have the appearance of elbows.

Yield losses resulting from lodging vary considerably. Data indicate that losses up to 40% can result from lodging during the 10 days following heading. Furthermore, lodged plants are more prone to losses from diseases and insects. Pesticide applications are largely ineffective on severely lodged plants as only part of the target tissue is exposed to the spray. Lodging that occurs later in the season results in much less yield loss. However, kernel damage and sprouting can occur in lodged fields that become wet.

The main factors that predispose a crop to lodging are:

  • High levels of nitrogen - N causes lush growth and heavier plant tissue. Excessive N can cause stems to be weak.
  • High seeding rates - With high plant densities there is less space for roots of individual plants, therefore, root systems are usually less extensive and poorly anchored. The trend towards heavier seeding rates in small grains exacerbates the lodging problem.
  • Wet soil conditions - Excessive soil moisture limits root development. Furthermore, roots in these types of soils often suffer from root rot. Wet soils do not anchor the roots of a plant as effectively as a dry soil.
  • Tall plant types or varieties with poor straw strength - Taller plant types are more prone to lodging as their center of gravity is higher than shorter plant types. Sort varieties (dwarf types) tend to be the most resistant to lodging. Within all plant height types, however, there is variability for lodging resistance and some varieties are more prone to lodging than others. Although modern breeding programs screen their materials for lodging resistance, that does not mean that they all will have the same level of lodging resistance, nor does it mean you can manage them poorly and expect them to remain standing.
  •  

    GREEN SNAP IN CORN

    Corn development has been slow this year, and is just now approaching tasseling in many of the earlier planted fields. During this late vegetative stage corn is most sensitive to "green snap". Green snap is the term used to describe the breaking of rapidly growing stalks of corn. Unlike stem lodging in small grains that occurs near maturity, green snap in corn occurs during the early development of the plant. During these stages if conditions are conducive to rapid growth (i.e. water and nutrients are not limiting and temperatures are high), cell division and elongation occurs so rapidly that there is no time for the cell wall to fully harden.

    There are a number of factors that affect green snap. The most important are the timing and velocity of the wind and the hybrid that is grown. High levels of nitrogen during the vegetative stage of crop development can also increase the likelihood of this problem as can the use of growth regulator type herbicides such as 2, 4-D, dicamba, and clopyralid.

    Reports on how much yield loss can be caused by green snap vary considerably. Nevertheless, plants that are damaged by green snap at an early stage of development will almost certainly have reduced yield potential. Given the difficulty of managing the environment and the likelihood of high winds during critical stages of development in North Dakota, the most effective way of managing green snap is by growing a hybrid with known resistance.

    Joel Ransom
    Extension Agronomist for Cereal Crops
    joel.ransom@ndsu.edu

     

    FIELD PEA RELAY COVER CROP

    Field peas are a leguminous crop, able to use atmospheric nitrogen and fix it into a plant usable form in a symbiotic relationship with bacteria in the root nodules. Dry peas are typically harvested in late summer and fields are tilled in the fall or a late chemical burn down will prepare the field for next season. However, there are opportunities to capture the sunlight after the harvest of the field pea and turn this energy into biomass and nitrogen. A field pea relay cover crop system can be used. This is a system where field pea seeds that dropped to the ground at harvest time are encouraged to germinate and start growing just after the harvest of the main crop. The new plant growth and fixation of nitrogen can be used as an additional source of organic matter and a biological nitrogen source for the next spring seeded crop. The living pea plants also provide a soil cover and protect the soil from erosive forces. This system can make use of the left over growing season since field peas are tolerant to minor freezing temperatures and the plant will continue to grow until late October or early November. The plants will winter kill. In order for the relay cropping to work the seed needs to be incorporated into the soil. The methods to get the seed into the ground include light disking, use of a coulter harrow, or rolling the field to press the seed into the soil. There needs to be enough seed left after combining (3 to 6 seeds per square foot equal to 1 to 2 bushel per acre).


    Field pea stubble left after harvest (Blaine Schatz).


    Relay crop of field peas after harvest of the main
    crop
    (Blaine Schatz).


    Height of pea re-growth on October 16, 2008
    Carrington Research Extension Center
    (Blaine Schatz).

    The amount of biomass produced and total amount of nitrogen accumulated in the plant tissue depends upon the pea plant density, the timing of initiation of re-growth, soil moisture, rainfall, and the date of a killing frost event. Relay cropping can work well as the growing conditions in the fall are cool and favorable for nitrogen fixation by the pea which is a cool season plant. As the stimulated volunteer plants are following the main crop of field peas there will be high numbers of Rhizobium leguminosarum bacteria (inoculum) in the soil. Table 1 provides data on the above ground dry matter of the pea at the end of the season and the amount of nitrogen in the plant tissue. It should be noted that the pea plants, while they grow, will take up nitrogen from the soil as well as fix atmospheric nitrogen. The stimulated "volunteer" crop can be used as a plough down, winter soil cover, or can be grazed. However, do not expect to harvest a second dry pea crop for seed as there is not enough time for the crop to mature.

    Table 1. Biomass, percent N in the plant tissue, and total nitrogen
    in the above ground plant tissue, Carrington, 2008.

    Field Number Total above ground plant dry matter at the end of the season Percent Nitrogen in the plant tissue Nitrogen in the plant tissue
     

    (lb/a)

    (%)

    (lb/a)

    14B

    3026

    4.3

    130

    14A

    1582

    4.0

    63

    12

    1877

    3.7

    69

    Blaine Schatz
    Agronomist
    Carrington Research Extension Center

    Hans Kandel
    Extension Agronomist
    hans.kandel@ndsu.edu


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