Influence of temperature and soil moisture on leaf area and dry matter accumulation during establishment of pea, maize and sunflower

Abstract

Leaf area expansion and accumulation of dry matter during the establishment of pea (Pisum sativum L., var. Ballet), maize (Zea mays L., var. Lorena) and sunflower (Helianthus annuus L., var. Florasol) were studied at different temperatures and soil moisture contents in a Vertisol (Lisboa)and a Luvisol (Évora) from June 1995 to November 1996. Measurements were made of soil temperature at 2 and 4 cm depth, air temperature and soil water content. Leaf area per plant was estimated from measurements of the length and width of each leaf. Above ground seedling dry matter was weighed after oven drying. Data analysis was based on the thermal time concept.

For water contents above 50% of the available capacity of each soil, leaf area of pea and maize increased linearly with accumulated temperature while that of sunflower increased exponentially. Dry matter of all crops increased exponentially with accumulated temperature. Significant differences between the two types of soil were found on the initiation of leaf area expansion of pea and sunflower, on the thermal-rate for leaf area expansion of maize and on the dry matter accumulation of pea and maize seedlings. The initiation of leaf expansion of pea occurred earlier in soil Cb while that of sunflower occurred earlier in soil Pmg. Leaf area expansion of maize was faster in soil Pmg. Dry matter accumulation of pea was faster in soil Cb while that of sunflower was faster in soil Pmg. In both soils, low soil water contents reduced leaf area expansion and dry matter accumulation of the crops.