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Northern Illinois Agriculture

University of Illinois Extension
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Planting underway in Northern Illinois


Powerful storms traversed Northern Illinois last week, limiting field operations, but reports of corn going into the ground in areas that missed the precipitation are trickling in. Most farmers will be anxious to start planting when field conditions now become suitable. We managed to plant our first corn at the Northern Illinois Agronomy Research Center on April 7th, earlier than our recommendations for this part of the state suggest. The 4" soil temperature under bare soil at our site measured 46 degrees, below the minimum 50 degree soil temperature where we expect corn germination to begin.  We checked that corn today and radicle emergence from the kernel has just begun. The corn was planted as part of our date of planting study conducted annually with both corn and soybean. For each crop we plant four dates and include a fungicide component to the trial. With our corn, we plant both an early and full season hybrid. Results from the 2014 corn study show no significant variation between our three early planting dates, and yield did not drop off until we reached our final late May planting date.

As farmers fine tune planters in preparation for the 2015 cropping season the topic of cost effective planting populations with reduced commodity prices has recently arisen. Dr. Emerson Nafziger shared the following comments at the Northern Illinois Crop Management Conference. Based on research trials conducted by the University of Illinois, high planted corn populations (up to 50,000 plants per acre) have shown a decrease in corn yields in recent years. They dropped less going from 42,000 to 50,000 plants per acre in 2014 in 2013. Not unexpected with our almost ideal weather conditions experienced last year. Yields going from 34,000 to 42,000 increased little at most sites, typical of recent years. It should be noted that hybrids differ some in this regard. Dropped populations that "pay their way" by producing enough (extra) yield to cover (extra) seed cost tend to be in the 30,000 to 35,000 range, without much correlation with yield level. The idea that we need to go to 40,000 to 45,000 with current hybrids is not supported by our current research.

What about planting depth? The Illinois Agronomy Handbook shares that ideal planting depth varies with soil and weather conditions. Emergence is more rapid from relatively shallow planted corn, so early planting should not normally be as deep as later planting. For most conditions, corn should be planted 1-1/2 to 1-3/4 inches deep. Early-planted corn should be in the shallower end of this range. Later in the season, when soil temperatures are higher and evaporation is greater, planting as much as 2-1/2 inches deep to reach moist soil may be advantageous, especially if the forecast is for continued dry weather. Planting depth studies show not only that fewer plants emerge when seeds are planted deep but also that those emerging may take longer to reach the pollination stage and may have higher moisture in the fall. Deeper planting also brings more danger of reduced stand due to crusting or wet soils and an increased chance of uneven emergence which can cause yield loss.

Activities at the NIARC today included flagging a nitrogen plot and evaluating an annual ryegrass variety trial.



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