SOIL TEMPERATURE AND MOISTURE CONDITIONS IN RELATION TO THE GROWTH AND QUALITY OF FIELD PEAS

Abstract

Cooking quality of two cultivars of field peas (Pisum sativum L.), Kapuskasing 3880-4 and Weitor 702, changed markedly when grown under different soil temperature–moisture conditions in a field environment modified by circulating chilled and heated water through pipes buried in the soil. Quality of Kapuskasing for "puree" soup was "poor" at the low temperature of 10.4 C but improved to "very good" at the warm soil temperature of 29.2 C (20-cm depth), whereas the quality of Weitor remained "good" to "very good" for both cool and warm soils. The quality for both cultivars appeared to be associated with the concentration of 2% HCl soluble-Phytin, Ca/Phytin-P, Mn, and K. In the top growth, the concentration of P generally increased with higher temperature and moisture regardless of yield levels. Concentrations of Mn and Fe consistently decreased with high moisture contents and that of Fe and Zn increased with higher soil temperature. Maximum vine weight for both cultivars occurred at the seasonal mean daily soil temperature of 18.5 C (20-cm soil depth) when moisture stress was kept low. The weight was less at lower (10.4 C) and higher (29.2 C) soil temperatures. Pea yields for both cultivars were highest, however, at the coolest temperature, and as the soil became warmer the reduction in yield was greater for Weitor than for Kapuskasing. Moisture stress considerably reduced growth and pea yields. The total amount of organic residues in the soil varied only slightly among the cool, seasonal, and warm soils. When separated into particle-size fractions by wet sieving, the amount of organic carbon in the fraction > 2.0 mm was much higher for the cool than for the warm soil, whereas the amount in the fraction 0.25–1.0 mm was higher for the warm soil. Thus, change in growth and quality of peas may be greater for some cultivars than for others when grown in different climatic regions, or when soil temperature conditions are changed by management practices. Such a management practice might involve using hot water discharged from the cooling operations of thermal power stations by distributing it through pipes embedded in the soil. However, if soil temperatures were raised, adequate water for irrigation would need to be provided for the greater evapotranspiration loss resulting from the induced higher soil temperature.