David L. Coffey

Mathematical formulae for calculating the base temperature for growing degree days

Much research has been done on finding methods to determine the base temperature, a very important variable in computation of growing degree days (GDD). Four common methods have been reported often in the literature: (1) the least standard deviation in growing degree days; (2) the least standard deviation in days; (3) coefficient of variation; (4) regression coefficient. The procedures to calculate the base temperature associated with these methods are tedious and lack a theoretical basis in mathematics. The objective of this research was to find simple and mathematically sound formulae to calculate the base temperature for GDD. Mathematical formulae are proposed, proved and tested using temperature data for snap bean, sweet corn, and cowpea. Compared with previous procedures, these proposed mathematical formulae can produce the base temperature easily and accurately. These formulae are applicable to calculating the base temperature for GDD of any developmental stage for any crop.

Growth response of selected vegetable crops to spent mushroom compost application in a controlled environment

SummarySnap bean, cucumber, radish, spinach, and tomato seedlings and plants were grown in soils amended with 0, 10, 20, 30 and 50% spent mushroom compost (SMC) under greenhouse conditions. While total seedling emergence was not affected by the addition of SMC, the rate of seedling emergence was delayed. Increased growth was observed in the range of 30 to 50% SMC. The elemental content in seedling tissue indicated an antagonism among K, Ca, and Mg for ion uptake. Increased plant growth and yield were obtained with addition of 20 to 30% SMC; those grown at 50% SMC exhibited some stunting. The limiting factor in the use of SMC appeared to be its high soluble salts content.