Growing Degree Days Through June 12

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu

Most corn at the station is starting to pull out of the sulfur deficiency with the sidedress application. We have seen 3-5 days between leaf stages since plants hit V6 and temperatures remained higher. If you planted corn in early April, you should be close to the V12 stage (Table 1). It will be difficult to count leaf collars, as after V6 the bottom one or two leaves may have dropped off. Some of our plots in Georgetown planted on April 24^th are at V9/10, so with 19-20 growing degree units per day, we could hit V12 early next week.

Any corn planted later in May through early June should be at or close to V5/6 and ready to sidedress, so be sure to scout those fields. We have noticed less sulfur deficiency with later planted fields, possibly due to S being available as it is released from organic matter with warmer temperatures. Let us know where you have seen S deficiencies this year. An application of gypsum as a starter to some of our plots did not reduce visual symptoms, we will have to wait and see if it helps with yield.

Day and nighttime temperatures for corn growth (Figure 1) have been great so far, plenty of warm days and cooler nights to keep growth at a maximum. Rainfall has had an almost linear increase (Figure 2) since April 14^th, with periodic storms keeping soil moisture up. Newark received almost 2 inches over the weekend, but otherwise, most regions are doing much better than this time last year.

Table 1: Accumulated growing degree-days based on planting dates through June 12^th.

V6 = 475 GDD, V12 = 870 GDD, VT = 1135 GDD, R1 = 1400 GDD

Figure 1: Statewide temperatures since April 1^st.

Figure 2: Statewide rainfall accumulation since April 1^st.