Evaluation of Double Crop Corn in Eastern Virginia
Crop and Soil Environmental News, January 1998
H. Behl, research specialist;
E. Bender, research associate;
D. Brann, Extension specialist, grains;
D. Moore, Extension agent, Middlesex County;
L. Barrack, research specialist
Double cropping corn for silage after small grain silage is practiced on a number of farms in Virginia. Double cropping corn for grain after small grain harvest for grain is not currently practiced. This research was initiated to ultimately develop a cropping system for continuous double cropping. This system may be especially well-suited on soils that are too droughty to produce only a summer crop profitably. The cropping system will emphasize well-managed wheat, barley, or some other winter annual.
Corn hybrids with a relative maturity from 75 to 115 days were planted at Corbin Hall near Saluda and on the Eastern Virginia AREC near Warsaw, Virginia at the time of barley harvest. The plots at Warsaw were planted conventional tillage whereas the plots at Corbin Hall were planted no-till. Nitrogen at 125 lb N/acre was applied at planting at Corbin Hall and 150 lb N/acre at Warsaw. No insecticide was applied.
Amazingly, corn was 5-6 inches tall two weeks after planting, 5 feet tall one month after planting, and beginning to tassel 55-65 days after planting. Excellent quality corn grain yields of 100 to 150 bu/acre were obtained both non-irrigated and with supplemental irrigation.
Corn hybrids with a relative maturity less than 90 days produced nearly 50% less yield than hybrids in the 100-115 day relative maturity range. Fortunately, corn hybrids with a relatively maturity of 100-115 days will be less than 25% grain moisture by mid-October even when planted in mid-June. We will not have to plant extremely early corn hybrids to fit double crop corn into a continuous double crop system.
When planted in mid-June in eastern Virginia the 91-105 day hybrids may yield similar to 106-115 day hybrids over years because the 91-105 day hybrids initiate tasseling during longer days. The ultimate yield-determining factor will be rainfall and available moisture at silking and tasseling. It may be advisable to plant at least two hybrids with different maturities to spread risk of drought at silking.
The study at Warsaw compared corn with Group IV soybeans (Table 29). The best corn hybrids yielded 122-126 bu/acre, whereas the two soybean varieties averaged 37 bu/acre, and the best grain sorghum averaged 141 bu/acre. At current prices, the net profits from the above three species would be similar. Two factors need to be considered. Double crop soybeans work extremely well and our goal is not to beat soybeans but to add another alternative for long term rotations. Second, the grain sorghum did extremely well this year and was sufficiently dry to harvest due to low rainfall and high temperatures for two weeks prior to harvest. Grain sorghum is normally slow to dry in the field and cannot be harvested and dried above 20% moisture.
European corn borer pressure was low at these locations this year. Corn earworm pressure was relatively low but the number of damaged ears at Corbin Hall was lower when comparing iso-lines such as N6800 with N6800 Bt(11). It is also interesting to note that the top 5 hybrids non-irrigated as well as supplementally irrigated had the Bt gene incorporated.
Further research must be conducted to evaluate the importance of insect resistance in selecting corn to be planted double crop in eastern Virginia.
In summary, 1997 results showed that double crop corn behind barley can be successful. The degree to which it is successful long term will be determined by further research and producer experience.
Table 27. Double crop study at Corbin Hall in 1997 - Non-Irrigated.
|Site was planted June 10 and harvested October 21, 1997. Leaf damage, European corn borer stalk and ear shank ratings, and number of ECB larvae evaluations were made on each hybrid by Dr. Rob Youngman, Extension Entomologist at VA Tech. There was little to no damage in any plots. The corn ear worm ratings were also made by Dr. Youngman. Sorghum at this site ranged in yield from 70 to 80 bu/acre.|
Table 28. Double Crop Study at Corbin Hall in 1997 - Irrigated
|Site was planted June 10 and harvested October 21, 1997. Irrigation included 0.75" applied three times during the growing season. There was one storm near the end of July that provided 3" of rain. Complete rainfall data is unavailable. The relatively high LSD is related to the fact that there was space for only two replications in the irrigated area.|
Table 29. Double crop study at Warsaw in 1997 - Non-Irrigated
|Asgrow AG4341||39||Group IV||12.2|
|European corn borer ratings on the corn plots were made by Dr. Rod Youngman, Extension Entomologist at VA Tech. There were essentially no corn earworms or European corn borers present in these plots. Site was planted June 17 and harvested October 14, 1997. Rainfall data for this site is as follows:|