Winter Forage Fertilization

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Our forage crops look much better now than they did this time last season. October was dry just like last season, but some soil had enough moisture to get a stand though mid October. Last year, frosts and rain hurt us. We checked some oats for aphids and found none this week. Aphids were also a big issue this time last year.

We are talking about fertility programs in our forage crops compared to our grain crops this week. When we plant wheat for grain, we go out with our recommended N based on previous crop at planting. We then check the stand in January to see how tillering is doing. If we have enough tillers, we hold off and put out the rest of our nitrogen at one time. If tillers are low, we split nitrogen to encourage tillering.

The difference in our forage crop UGA Extension Forage Scientist Dr. Dennis Hancock says that we only intend to increase our vegetative growth. With grain, we want to count tillers and fine tune our nitrogen. “With forage we want apply 40 – 50 lbs of N per acre at planting or soon after the plants emerge to increase growth, tillering (thickening of the stand), and provide earlier grazing. A second application of 40 – 50 lbs of N per acre should be applied in mid-winter to increase winter and spring forage production. Because ryegrass is longer-lived, a third application of 40 – 50 lbs of N per acre may be needed in early spring when ryegrass is used for late spring grazing, hay, or silage crop. Rates of N in excess of these amounts may result in substantial N losses to leaching and excessive growth during the winter. Fresh, tender growth that occurs when nitrogen is in excess could be damaged by extremely cold weather.” More information on fertilization can be found on the Georgia Forages website.

As weather turns colder, there are some issues we will have in our grazing crops. Most fields this year are oats, rye, ryegrass or a blend. Oats are more susceptible to cold injury than other small grains. With cold injury, we will see purpling of the foliage. The purpling is the result from accumulation of anthocyanins after temperature drops. We do not expect permanent damage, as the growing point is below ground during the tillering stage until jointing.

Purpling due to cold injury in oats

Purpling due to cold injury in oats

This reddish/purple color can also indicate barley yellow dwarf virus. These symptoms start from the tip of the leaf blade. The virus is vectored by aphids which are observed on the foliage. Most fields will have some level of BYDV each season. We are not seeing aphids now, so this is less of a concern.

Another cause of purpling is due to phosphorus deficiency. P is not soil mobile and is taken up by root ‘interception meaning’ the roots must grow to it. Cold can decrease root growth and this becomes evident. Nitrogen and potassium on the other hand are soil mobile. They can leach down into soil profile with rain. This time last season, rain was leaching N out of the soil. N is also mobile inside the plant, so older or lower leaves will show deficiency first.

Nitrogen deficiency in wheat

Nitrogen deficiency in wheat

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