NDSU Crop and Pest Report

Plant Science


ISSUE 5  May 30, 2002

 

STUBBLE HEIGHT EFFECTS IN ALFALFA

Leaving 3- to 5-inch alfalfa stubble height during harvest is very common because of rocks, pocket gophers, or lodging. But what is the impact of stubble height on the yield and quality of alfalfa? Obviously, increasing the stubble height will reduce forage yield, but it is surprising by how much.

Three experiments evaluating stubble height effects have been conducted over the last five years, two at Fargo (dryland) and one at Carrington (irrigated). Forage yield averaged across the first two years of production has been reduced 1.04 tons/acre for each 2 inches of stubble left in the field when forage yield of the 1-inch stubble height yielded 6.69 tons/acre. Thatís a 15% reduction in forage yield for 2 inches of stubble left in the field or 30% for leaving a 5-inch stubble. This 30% yield reduction in these experiments was greater than the state average alfalfa yield!

Harvesting at the higher stubble height increases the forage quality of the hay. The relative feed value (RFV) of the hay increased 31, 30, and 26 units in the first, second, and third harvests, respectively, when harvested at 5 compared with 1-inch stubble height. Likewise, crude protein (CP) increased 2.2, 2.6, and 1.4% in the first, second, and third harvests, respectively. Obviously, the lower stem (lowest 4 inches) is very poor in forage quality averaging only 10.1% CP, 51.3% acid detergent fiber (ADF), 61.5% neutral detergent fiber (NDF), and RFV of 71 in the first harvest. The hay averaged 19.8% CP, 31.7% ADF, 41.7% NDF, and 144 RFV (nearly prime hay). However, the forage quality of the lower stem improves with each harvest.

Each producer must weigh the advantages of yield, forage quality, harvesting efficiency, over-wintering ability, and economics when deciding at what stubble height to harvest the alfalfa. Cash hay producers receive a premium for high quality, so leaving some stubble in the field to increase quality might be justified if harvest is delayed by rain. However, I believe it is better to harvest when the lowest stubble height will produce prime hay rather than sacrifice yield potential. In many cases, the premium price received will not offset the 30% reduction in yield. Re-growth rate is not affected by the stubble height, but over-wintering of the four-cut system was slightly better in the 5-inch than 1-inch stands during the 2000-2001 winter. Beef cow producers should harvest as low as possible since forage quality of alfalfa is greater than needed in rations.

Stubble height at which alfalfa is harvested has a greater impact on forage yield and quality than what you might anticipate, and it should be considered in your management package. More effort on pocket gopher control is warranted. Removal of rocks prior to seeding or rolling to push rocks back into the ground in established stands is also warranted.

Dwain Meyer
NDSU Professor, Forage Management
dmeyer@ndsuext.nodak.edu

 

ALFALFA GROWTH IN 2002

Alfalfa growth this spring is considerably behind normal due to the much below-normal temperatures. My best estimate is that the alfalfa is two to three weeks behind the growth of the past 5 years. For example, we harvested alfalfa at the early bud stage (nearly 30 inches in height) on May 28, 2001, this year the alfalfa is only about 8 inches in height on the best fields.

Hopefully, temperatures will warm up soon so the alfalfa can add tonnage to the first harvest, however, first-harvest forage yields will be substantially less than the past several years. Due to the cold temperatures, we have lost nearly a month of growth. Therefore, first-harvest forage yields will be more comparable to normal second-harvest forage yields since the photoperiod and temperature will force blooming of shorter growth alfalfa. Harvest date on a calendar basis will be later than normal for alfalfa in 2002, but also the shorter growth will change the optimum growth stage at which to harvest. Two characteristics determine the optimum harvest stage of alfalfa; maturity stage and stem height. Since the temperatures have shortened the height of plants, the optimum maturity stage at which to harvest this year will be later than normal. For example, alfalfa harvest should begin when the relative feed value (RFV) of alfalfa is about 175. Alfalfa 30 inches tall will reach this RFV at the late vegetative growth stage, a 25-inch tall plant reaches this RFV at the late bud stage, while a 20-inch tall plant reaches this RFV at the late flower stage according to the PEAQ system.

Delaying harvest to more advanced maturity stages this year will allow for greater first-harvest forage yields and still allow the production of prime hay. Use the 25-inch height as an indicator. If greater than 25 inches of growth, harvest at a earlier growth stage and if less than 25 inches of growth, harvest at later growth stages.

Dwain Meyer
NDSU Professor, Forage Management
dmeyer@ndsuext.nodak.edu

 

ROLLING SOYBEAN, FIELD PEAS AND LENTILS

Soybean:

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 seeds 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 sotyledon 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.

Field peas:

Stones or soil lumps on the soil surface interfere with pea harvesting. Rolling allows for higher speeds when swathing or direct combining, and reduces guard and sickle section breakage. Peas can be rolled after harrowing or harrow packing if conventional tillage is used or after seeding if direct seeded. Heavy or excessive rolling with wet, heavy soils causes crusting which will interfere with emergence. In such cases, post emergent rolling prior to the 5 leaf stage should be used. All rolling should be carried out on dry days to lessen the spread of disease.

Lentils:

Lentil fields should be rolled to provide a smooth and level surface for harvest. Land rolling can be done before the crop emerges, but can lead to increased soil erosion if the soil surface is dry.

Research indicates that land rolling after the emergence of lentil can be successfully completed up to the five to seven node stage without significant yield loss. Land rolling past this stage can damage plants, increase the spread of foliar diseases, and reduce yield. Best results are obtained if rolling is done when plants are slightly wilted and the soil surface is dry. Rolling should not be done on wet soils or when the crop is damp or stressed by extreme heat, frost or herbicide application.

Duane R. Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu

Greg Endres
NDSU Area Extension Agronomist
gendres@ndsuext.nodak.edu

 

EARLY CORN SEEDLING GROWTH STAGES

As the 2002 corn crop grows and develops, one must understand the growth aspects of corn. This allows more timely management for nitrogen side dressing, rotary hoeing or cultivating or post-emergence herbicide applications. Once the corn seed absorbs water, it begins growth. The radicle (seed root) and plumule (seed shoot) both become visible. Emergence from the soil of the coleoptile is called the VE stage. Next stage is the V1 Stage in which the first true leaf with a rounded tip appears. All subsequent corn leaves have pointed tips. When the first rounded tip leaf has a fully formed collar, stage V1 has been reached. The collar is a yellowish band that extends across the leaf at its base. V2 corn would exhibit two visible collars. Successive leaves appear on opposite sides of the stalk. The V3 stage occurs when the third leaf from the base of the plant has a fully formed collar. At this time, the growing point is still below ground. Very little stem elongation has occurred at the V3 stage. The corn seedling is approximately 6-7 inches tall. From V2 to V5 stage, early side dress applications of nitrogen can be safely applied.

Destructive hail, wind or frost which damages the exposed leaves at V3 will have little or no effect on the below-ground growing point or final yield. Flooding however, at any time when the growing point is below the water level can kill the corn seedling in a few days if temperatures are high. After V5 and at V6 the growing point has moved above the soil surface. The stalk is beginning a period of greatly increased elongation. As the growing point comes to the soil surface, ear initiation has begun. Also, keep in mind that at the V6 stage, lateral roots can extend 12 to 14 inches each direction from the row. Root pruning can be a problem if the corn is cultivated too close with the shovels set too deep. With 22 inch row spacings this problem could be even more severe. See table below:

Vegetative and reproductive stages of a corn plant.

Vegetative Stages

Reproductive Stages

VE emergence

R1 silking

V1 first leaf

R2 blister

V2 second leaf

R3 milk

V3 third leaf

R4 dough

*

R5 dent

*

R6 physiological

*

Maturity

V (n) nth leaf

 

VT tasseling

 

Duane R. Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu

 

TIME TO PLANT BUCKWHEAT

Buckwheat is planted later than small grain, corn, beans, and sunflower. It is very sensitive to spring and fall frosts and any seeding should be delayed until all danger of frost is past. Best planting dates are from May 25 to June 10 in most years. Research date of planting studies at Langdon during 3 years indicated significant buckwheat yield reductions when seeding was delayed to June 22 or later.

It requires about 10-12 weeks after emergence to reach maturity. Buckwheat also is very sensitive to high temperatures and drying winds during blooming time in July and early August. Seedbed preparation is similar to flax. Delayed sowing permits killing several weed crops prior to seeding. Presently, no herbicides are labeled for use in buckwheat for weed control.

Under good moisture and temperature conditions, buckwheat shades the ground rapidly. A seeding rate of 40 to 50 lb A is recommended. Seeding depth of 1 to 2 inches is desirable in moist soil. Shallow seeding is desirable for rapid emergence. A conventional grain drill can be used and seed treatment is not necessary. Buckwheat has limited response to fertilizers. Itís a heavy user of phosphate with needs similar to wheat. Nitrogen application should remain low because of problems with lodging and delayed maturity. Buckwheat should be swathed when most of the seeds are ripe. In the event of frost, swath promptly to reduce shattering losses.

For more information on buckwheat production, request NDSU Circular A-687, available from your local county extension office or the NDSU Extension Distribution Center.

Duane R. Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu


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