a REVISITING HYBRID MATURITY ISSUES Greg Roth Penn State Agronomy Associate Professor Many growers throughout Pennsylvania were plagued by com that dried down slowly last year and resulted in late harvest, high drying costs, and sometimes low test weight com. This has caused many pro ducers to wonder if they are growing hybrids that are too t, * -aj ‘‘-8 ss’* : % , mk&mm late for their region. This is a very valid .question. But we need to realize that the slow drydown last year was also related to a cool season and drought stress. In many areas of the state, the growing degree days available for com growth and develop ment were less than normal. Growing degree accumulations from May 1 to October 1 for State College, for example, were about 2,150, about 300 GDDs less than normal for our area. To compound the prob lem, when com experiences drought stress, silking is often delayed.' Last year we noticed about a 4-5 day delay in silking at Rockspring because of the drought Basically, the com plants went dormant and we effectively lost another 100 GDDs or so. So, we had about 2,050 GDDs to mature a 2,400 GDD hybrid in. It was not sur prising that even our eariy planted hybrids failed to reach black layer and dried down slowly. In our area, we have found that it generally takes about 2,400 GDDs to get a 105-day hybrid to black layer. Frequent ly, this is about all of the GDDs we get. We can grow longer season hybrids, say 110-day maturity, that need about 2,600 GDDs. but they often only reach half milk Une. If we are harvesting for high moisture com, or want to harvest in December, we can utilize these hybrids. If we get a cool season, though, then the 105-day hybrid takes until December to Com Talk, Lancaster Farming, Saturday, March 7, 1998—Page 19 dry down and the 110-day hybrids can sometimes result in wet com and poor quality grain. These seasons are especially tough on grain producers who need to dry this com or those who want to utilize it for ear com. We could also grow 100-day hybrids that mature in 2,200 GDDs or so and very rarely encounter maturity problems, but in warm years we may sac rifice some yield potential. Also consider, though, these eariy hybrids have other advan tages: opportunities for plant ing wheat after harvest, drying com under warmer conditions, and harvesting under generally drier soil conditions resulting in less soil compaction. Several other factors compli cate the hybrid maturity ques tion. Probably more than any other state we have wide matur ity difference within many counties. So on one side of the county you might be able to get away with a hybrid 5 to 10 days longer than on the other side. Another factor is lack of standardization on com hybrid maturity—a 105-day hybrid in one company is not the same as a 105-day hybrid in another company. Another factor is that we rarely get a normal year and it is easy to let what hap pened last year dictate your decision too heavily. A fourth factor to add to the confusion is that seed company ratings for hybrid GDD requirements are often higher than their actual requirement by 200 GDDs or so—many of the 105-day hybrids have a GDD rating of 2,600. So how can we try to make a better decision on the maturity of hybrids we grow? First, decide if this is an issue for you. If you have not had trouble with slow dtydown or test weight in the past few years, then you're probably all right. If you have, then consider evaluating some earlier hybrids in your mix. One good way would be to estimate the GDDs available in your area. Next try to match your real hybrids GDD needs with the available GDDs. Also consider a spread of maturities to help offset the risk associated with warm or cool seasons. A good suggestion might be 20 percent that always mature (early season). 60 percent that usually mature (medium sea son), and maybe 20 percent that sometimes mature (full sea son). Then adjust that based on your own operation. If you harvest all grain and test weight is a critical issue, move more toward the early hybrids. If you sell high moisture grain and can tolerate more risk, perhaps you can move toward the fuller sea son hybrids. Also start to do a little matur ity monitoring on your own. Are the hybrids you are grow ing reaching black layer regu larly? If not, then you are likely near or past your limit on maturity for shelled or ear com harvest Are you encountering other problems associated with late harvest—soil compaction, late-planted wheat or difficulty completing harvest before the snow flies? Are you not seeing a yield advantage to the longer hybrids? If so, these signal a move toward an earlier maturity. Com maturity decisions are not always as simple as they should be. Take time to re evaluate your situation. Don’t make knee-jerk reactions. Base your decisions on sound obser vations and long-term weather
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