ISSUE 9   June 30, 2005

LODGING IN CEREALS

Lodging in cereals generally is most problematic as they start to mature. Nevertheless, the high winds and rain this past week, coupled with excessively wet soils, resulted in considerable lodging throughout the state.

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, like this year, 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. Some data indicate that losses of up to 40% can result from lodging during the 10 days following heading. Furthermore, lodged plants are more prone to losses from diseases and insect infestations. Pesticide applications are largely ineffective on severely lodged plants because only part of the target tissue is exposed to the spray. Lodging that occurs later in the season results in much lower 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. The resulting root systems are usually less extensive, leaving plants poorly anchored. There has been a trend towards heavier seeding rates in small grains in an attempt to intensify production. One of the down sides of excessive plant populations is an increase in the potential for lodging. Lodging was reportedly the most severe this past week in experimental plots at Carrington where seeding rates were on the high side.

Wet soil conditions - Excessive soil moisture limits root development. Furthermore, roots in these 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 - Plants with tall growth habits are more prone to lodging because their center of gravity is higher than shorter plant types. Almost without exception, short varieties (dwarf types) are the most resistant to lodging. Within all plant height types, however, there is variability for lodging resistance, and some varieties are just 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 one can manage them poorly and expect them to remain standing.

 

GREEN SNAP IN CORN

The recent heavy winds that caused so much lodging in small grains also caused "green snap" in corn. 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. Corn is most susceptible to green snap during the 5-8 leaf and the 12-leaf to tasseling stages. If conditions are conducive to rapid growth (i.e. water and nutrients are not limiting and temperatures are high) during these stages, cell division and elongation occur so rapidly that there is no time for cell walls to fully harden.

A number of factors affect the occurrence of 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 were damaged by green snap at this 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
NDSU Extension Agronomist
Cereal Crops
joel.ransom@ndsu.edu

 

DRY BEANS: GROWTH AND MATURITY

Two basic plant types are found in dry edible bean, determinate (bush) or indeterminate (vining or trailing). Cultivars may be classified according to plant types. For example, navy beans may be either of the bush or vining types. In the determinate type, stem elongation ceases when the terminal flower racemes of the main stem or lateral branches have developed. On indeterminate types, flowering and pod filling will continue simultaneously or alternately as long as temperature and moisture permits growth to occur.

The question of dry edible bean maturity has been debated for many years. Compared to many other plants, the dry edible bean is orderly in its growth and development. There are two basic stages of growth: vegetative and reproductive. Growth at any point in the vegetative stage can be determined and defined by counting the number of nodes on the main stem. The reproductive stage begins when the first flower opens, and is described and characterized by observing pod development and seed fill within the developed pod. Both vegetative and reproductive stages can further be separated into two periods for a total of four major growth periods in the life of a bean plant.

They are:

  1. Germination and stand establishment (V1 to V2)
  2. Rapid vegetative growth (V3 to V8)
  3. Flowering and pod development (R1 to R4)
  4. Pod fill and maturation (R5 to R9)

The time required for the two growth periods of "germination and stand establishment" and "flowering and pod development" under the same growing conditions is the same for all varieties. Differences in maturity of varieties are experienced during the two periods of "rapid vegetative growth" and "pod fill and maturation." The way it works is that late-maturing varieties require a longer period of time to pass through the "rapid vegetative growth" period than will early maturing varieties. This increase in time results in increased vegetative growth, and enables plants to produce and fill pods over an extended period of time.

This sounds simple and straight forward, and leads one to wonder why two people can come up with a different maturity value for the same bean variety. The reason seems to be that maturity for a given variety may be extended during one or more of the growth periods.

The developing bean will respond to many factors, including planting in cool and/or wet soils, planting in dry soils, insufficient soil moisture, excessive soil moisture, high temperatures during flowering which delays pod set, or low temperatures during maturation. Maturity of a variety may also be extended by preplant herbicide injury, excess of or lack of certain plant nutrients, low plant stands, beans following alfalfa in a rotation, or damage from hail. Some of these factors can be controlled, others cannot. It's important to consider these factors, however, when comparing differing maturity dates for a bean variety. One of the above factors will usually be responsible for the difference.

 

OIL SEED SUNFLOWER DEVELOPMENT

Sunflower growth and development responds to heat units similarly to corn and several other crops. The base temperature of 44EF is used to determine Growing Degree Days (GDD). GDD formula = [(daily maximum temperature + daily minimum temperature)/2] - 44 degrees F.

Research data in the following table was collected at the Carrington Research and Extension Center over a number of years on sunflower stage development and heat units.

Oil sunflower development by days and growing degree day (GDD) units, 1994-95, Carrington Research Extension Center*

Sunflower
stage

Average days and GDD units increase from previous stage

Average days and GDD units accumulated from planting

 

days

units

days

units

VE

10

167

10

167

V4

10

182

20

349

V8

8

196

28

545

V12

6

145

34

690

V16

5

82

38

772

V20

6

99

44

871

R1

2

49

46

919

R2

15

333

61

1252

R3

6

142

67

1394

R4

4

99

71

1492

R5.1

3

54

73

1546

R5.5

4

77

77

1623

R6

8

158

84

1780

R7

12

272

96

2052

R8

9

159

104

2211

R9

15

259

119

2470

Planted on May 25 in 1994 and May 23 in 1995. Growing Degree Days were averaged over 5 hybrids each year and 5 plants per hybrid per plot were observed.

GDD units/data for 2005 can be found on NDSUís Extension site under Ag weather (NDAWN). Just click on the "applications" section, select "sunflower", and then "Degree Days".

Dr. Duane R. Berglund
NDSU Extension Agronomist
duane.berglund@ndsu.edu


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