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CS 462 Heat Units and Peanuts

CS 462 Heat Units and Peanuts - Determining pod maturity of...

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Unformatted text preview: Determining pod maturity of peanut The indeterminate nature of peanut contributes to the challenge of deciding when to dig and invert vines in order to optimize pod yield and market grade characteristics Progression of maturity of peanut pods using pod mesocarp color We tell the farmer when we think the peanuts will be at optimum maturity. The farmer decides when the peanuts are "ready" to dig. Predicting Pod Maturity Pod mesocarp color determination Heat unit accumulation Assumes "normal" growth and maturation Requires "ample" moisture to ensure normal growth and maturation "dry heat" Critical levels of temperature if it cools down sufficiently at night can the crop "retool" even when temperatures during the day are warm? Heat Unit Calculations Several techniques and levels of sophistication - Heat units are calculated using day degrees from emergence through optimum maturity. - Subtract 56 from the average of the highest and lowest daytime temperatures. - This number, added throughout the season for each day, will give the amount of heat units available for growth and development. - Assumptions: no growth and development below 56oF (a ceiling is placed on temperatures that exceed 95oF) and adequate soil moisture is available during the season for normal plant growth and development. Influence of Digging Date on Peanut Pod Yield (Variety Gregory Lewiston in 2003, 2004, and 2005) DD56 assumes 95 degree ceiling and 56 degree floor and is the average of the daily high and the daily low from emergence to digging 154 days 2670 DD56 2676 DD56 (130 days) 2739 DD56 (134 days) 2804 DD56 (141 days) 129 days 2626 DD56 130 days 2658 DD56 DD56 units Period 2003 2368 913 2004 2522 1153 2005 2338 818 May-Aug May - June 2512 DD56 (121 days) 2739 DD56 (129 days) 2822 DD56 (136 days) 7000 6000 pounds/acre 5000 4000 3000 2000 1000 0 2003 - B4 May 5 Sep. 13-14 Sep. 17-23 Sep. 24-31 Oct. 1-6 Oct. 8-13 Oct. 15-20 2004 - F1 May 6 2004 - G2 May 10 2004 - A2 May 6 2005 - F2 May 2 Planting date Influence of Digging Date on Peanut Market Grade Characteristics of the Cultivar Gregory Data are pooled over five experiments Lewiston - 2003, 2004, and 2005 100 90 80 70 60 50 40 30 20 10 0 Sep 13-14 Sep 17-23 Sep 24-31 Oct 1-6 Oct 8-13 Oct 15-20 Percent ELK TSMK Fancy pods Although quality factors improve when digging is delayed, there are fewer pods on the plant as time goes by, and eventually no pods are on the plant to replace those that shed. Eventually yields will decrease. Heat Unit Accumulation Variety CHAMPS Wilson VA 98R NC 12C Gregory NC-V 11 Georgia Green Phillips Perry Relative ranking in maturity (days) -9 -7 -5 -3 0 0 +3 +3 +7 Heat units 2500 2520 2560 2600 2650 2650 2700 2720 2770 ...
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