ISSUE 12   July 30, 2008

FIELD PEA HARVEST

Pea fields may have some weeds or later maturing plants and a decision needs to be made about swathing the crop prior to harvest. Start swathing when the vines are yellow colored and the seeds should be firm, but not hard. Pickup guards and or pickup reels with sharp sickles should be used.

If peas will be directly combined, set the pickup for aggressive picking. The coulters should be sharp and the chains tight. Combine the dry field peas at 16 to 20% moisture in order to reduce splitting of the seed or cracking of the seed coat. The cylinder speed should be from 350 to 500 RPM’s using the lowest speed that circumstances allow. The concave should be opened as wide as possible while still removing all the seeds from the pods. The cleaning fans should be set high with sieves open so pods will not end up in the grain tank. If the combine has a chopper, set it in such a way that it will cut aggressively and spread the cut pea vines and chaff as evenly as possible. Field peas should be handled as gently as possible especially if the peas will be used for seed next year. Run the unloading auger on the combine full and slowly to avoid seed damage. In further handling use conveyers to fill the bins or if an auger is used make sure the auger is full and runs slowly. Provide aeration to dry the field peas down to 14% moisture in order to avoid spoilage of the valuable crop.

After harvesting the crop, the field could be worked lightly to stimulate the germination of un-harvested pea seeds and create a volunteer "green manure." The volunteer field pea can make use of the sunlight and fix some atmospheric nitrogen. The green manure crop can be mechanically terminated at the end of the growing season or can be left and it will be killed by the frost.

 

LENTIL HARVEST

Lentils can be swathed when one-third to two-thirds of the field is golden in color. The lower pods on the plants should be fully mature and drying. Use a pickup reel and pickup guards. The best time to swath is in the early morning or late evening when the relative humidity is higher than during the hottest part of the day. The higher humidity may help in reducing shattering. As lentils are a relatively short crop there will be little stubble left after cutting and the swath may be susceptible to blowing. The use of a swath roller may cause excessive shattering and its use is not advised. It is important to harvest the lentils as soon as possible after swathing, but to allow time for the pods to dry until the seed moisture has reached the 16 to 20% moisture level. Adjust the pickup speed to match the combine groundspeed. The cylinder speed should be adjusted according to the conditions during thrashing and should be between 250 to 650 RPM’s. Use a cylinder speed to just break open the pods without splitting or damaging the lentil seed. The concave setting should be similar to harvesting wheat and barley and should be adjusted according to the harvest conditions. Adjust the cleaning fan similar to that of wheat or barley harvest settings. Lentils are a little more forgiving during handling than field peas, but still split lentils or damaged seed coats are unwanted. Augers should be full and run at reduced speeds. The lentils should be dried down for storage to 14% moisture, be careful however to prevent over drying which will increase the chance of splits and broken seeds when unloading the bin at the time of sale.

Hans Kandel
Extension Agronomist - Broadleaf Crops
hans.kandel@ndsu.edu

 

CORN GROWING DEGREES STILL LAGGING FAR BEHIND NORMAL

As we approach August and the prospects of shorting days and fewer growing degree days per day, it is now prudent to take of stock of where we are at with regards to corn development. It is obvious as you travel around the state, that corn development is far behind where it was last year. In fact, corn is just now beginning to tassel which compares with most fields tasseling in mid-July last year. A quick look at map of corn growing degree days (GDDs) on NDAWN shows that depending on the location in the state, GDDs are currently running about 100 to 150 behind the long term average when a May 1st planting date is assumed. In this article GDDs from Jamestown and Oakes will be used to illustrate the impact of the cool weather this year on corn development and the risks of insufficient GDDs on the corn crop this fall. As of yesterday (July 27th) Jamestown and Oakes were 211 and 112 GDDs behind the long term average, respectively (see Table 1). Generally, yield is not impacted by slow corn development. In fact, the lack of extremely hot days this summer has probably been beneficial to the crop as far as yield is concern. The problem with cool weather and slow corn development is that the crop may not reach physiological maturity before the first killing frost, but perhaps more importantly the grain will be so wet at harvest it will be difficult to handle and expensive to dry.

So how do GDDs translate in terms of calendar days and how far behind normal are we? During late July, daily GDD accumulations run about 20 per day, which means that we would need an extra five to ten "July days" (for Oakes and Jamestown, respectively) to catch up to the long-term average. To look at it another way, since a corn hybrid with a relative maturity of 85 requires about 1150 GDDs to silk and 2100 GDDs to reach physiological maturity (PM) (see Table 2) we have accumulated slightly over half the required GDDs to reach PM. Since in a normal year GDD accumulations from now to October 1 are just under 1000 (see Table 1) an 85 RM hybrid would probably reach PM if the first killing frost is delayed until then. A 95 RM hybrid, on the other hand would not reach PM if normal accumulations are assumed. Grain dry-down is another issue. From research funded by the Corn Council that was conducted last year, we found that about 150 to 200 GDDs are required to dry corn in the field from 35% to 20% moisture. Using normal GDD accumulations for October (Table 1), and assuming a crop reaches PM on October 1st, corn will not reach 20% moisture by November 1st, except perhaps at Oakes.

Hopefully this data has helped you visualize and quantify the delay in corn development this year. Though the data does not suggest that we will see large yield losses due to crop immaturity this year (assuming a relatively normal first frost date and that recommended hybrid maturities were grown), they do indicate that corn will probably need substantial drying after harvest before it can be safely stored. Obviously, warmer than average weather will hasten corn development and reduce the impact of our cool spring. Since we are dealing with "average" weather data, large deviations from the normal can be expected. A prolonged warm and dry fall, like we had in 2007 would be beneficial in reducing the need for drying time. On the other hand, cooler than average temperatures, during the remainder of the season, could exacerbate an already difficult situation.

Table 1. Corn growing degree day (GDD) accumulations, their deviation from normal and normal accumulations for the remainder of the growing season and for November, Jamestown and Oakes, ND.

Location

GDD accum. (5/01 to 7/27)

Deviation from normal (GDDs)

Normal accum. (7/27 to 10/01)

Normal accum. (10/01 to 11/01)

Jamestown

1102

-221

978

102

Oakes

1229

-112

973

150

Table 2. Typical GDD accumulations needed for hybrids of three differing RMs to reach silking and physiological maturity (PM).

Hybrid RM

Planting to silking

Planting to PM

85

1100

2100

90

1150

2200

95

1200

2300

Joel Ransom
Extension Agronomist - Cereal Crops
Joel.ransom@ndsu.edu


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