Soil Temperature and Wheat Straw Mulch Effects on Wheat Plant Development and Nutrient Concentration 1

Hard red winter wheat ( Triticum aestivum L.) was grown with and without wheat straw mulch on the soil surface both in a growth chamber with controlled soil temperatures and in the field where soil temperatures were measured at the crown depth. Concentrations of N, P, K, Ca, Mg, Fe, Zn, Mn, and Cu in the plant were determined at the end of tillering and at heading. Wheat plants grown with soil temperatures below 10C for 50 days, whether in the growth chamber or in the field, had 2 to 3 fewer tillers per plant and 0.5 to 1.2 fewer heads per plant than plants grown with soil temperatures below 10C for only 15 days. Soil temperature seemed not to affect weight per head or total plant weight. Cooler temperatures reduced the concentrations of only K and Fe in the growth chamber at heading and N in the field at heading. When mulched and bare soil temperatures were identical, mulch did not reduce numbers of tillers or heads per plant, plant nutrient concentration, total uptake of any nutrient, or final grain yields in growth chamber or field. The concentration of all nutrients but Cu changed as the plant developed showing the necessity of knowing growth stages of plants if nutrient concentrations are to be compared.