Cabbages to be harvested in the year-end season are transplanted in the previous summer, and frequently receive heat damage in their early period of growth. Aiming to reduce the damage, a cultural practice of transplanting on the northern slope of the ridge rows with their direction running east-west was evaluated.
　Temperature was decreased and water content was increased in the soil under the northern slope of the ridge rows. Leaf area increasing in the early period of growth between the northern slope and the conventional top-planting were analyzed in eight cultivars in a summer planting. The planting on the northern slope accelerated the leaf area increase in most of the cultivars, however the increase in the ratio of the northern slope to the top differed largely in the cultivars.
　The hydro-physiological characteristics of the higher ratios were analyzed in cultivars, comparing the xylem pressure potential vs. water content relation. The cultivars with high ratios held water much better in their bodies under the water stressed condition, showing high tolerance to drought. The effect of the tolerance appeared earlier in these cultivars transplanted on the northern slope of ridge rows than in those transplanted on the top, affected by the characteristics of their pressure-volume curves.
　Growth and yield in eight cultivars which had been planted on the slopes were compared to the top-planting in different cropping seasons. The northern slope planting was superior to the top-planting in the late spring, summer and early autumn transplanting, while inferior to that in the middle autumn. The largest disappointment of the northern slope planting was the flooding damage in the hot season.
　We confirmed the significant effect of a model of paper-pot transplanters for transplanting on the slope of ridge rows.

Direct seeding of rice is increasingly used to grow the most suitable cultivars under the best cropping schedule in the face of changing climatic and weather conditions. Although crop modeling can be used to optimize these factors, models developed for transplanted rice are not directly applicable, owing to differences in crop development due to weather conditions. Here, we present a method for estimating a parameter set for a crop development model applicable to direct-seeded rice from a set developed for transplanted rice. We hypothesized that model parameters C and D, which are related to the initial development index, can describe the difference in crop development between direct seeding and transplanting. The method estimates the values of C and D for each practice independently using shared parameters A, Th, and G, which are related to the temperature response of development and the days required for panicle initiation and heading in transplanted rice. We used data from field trials conducted in Iwate Prefecture between 2015 and 2019 with ‘Ginga no Shizuku’ to establish and verify the method. The estimated parameter set was accurate within a root mean square error (RMSE) range of 1.08 to 3.85 days at the heading stage and 2.96 to 3.11 days at the panicle initiation stage. When we tested the validity of the method by growing ‘Ten no Tsubu’ in both practices, the estimated parameter accuracy was 2.06 to 3.37 days RMSE at heading. We conclude that our method supplies a suitable parameter set for crop development models of direct-sown rice with an acceptable degree of accuracy. It will contribute to the estimation of optimal combinations of cultivars and cropping schedules for direct-sown rice under climate change, using historical field trial data and estimated parameter sets for transplanted rice.