抄録
Potato is known to produce stable tuber yield as compared with other field crops. For a better understanding this reason, we observed growth pattern and tuber yield in the two years (1982 and 1983) under different climatic conditions in the early half of the growing seasons. Five main cultivars, early to late, were grown and the observation was made at the same date in the both years. 1. Climatic conditions before early August were substantially contrast between the two years; they were dry with abundant radiation in 1982, while wet with short radiation and low temperature in 1983. After middle August, however, they became near to those of the average year in the both years (Fig. 1). 2. Growing period and tuber dry matter yield were not significantly different between the years, although tuber fresh yield was significantly larger in 1983 than in 1982 (Table 1.). Patterns of total and tuber dry matter accumulation were quite different between the years (Fig. 2). The rates of dry matter production in the early season were smaller in 1983. On July 15th, there were large differences in percentages of dry weight in each organ ; they were smaller in leaf and stem, and larger in tuber dry weight in 1982 than those in 1983 (Table 2). 3. Leaf area index (IJAI), crop growth rate (CGR), net assimilation rate (NAR) and tuber growth rate (TGR) showed quite different seasonal changes between the years (Fig. 3). LAI in 1982 and CGR, NAR and TGR in the early growing season of l983 were rather low values. Significant differences were also found in specific leaf area (SLA) between the years, the values in 1983 were higher than those in 1982 (Table 3). 4. During the experimental period, the solar radiation in 1983 amounted to only 75% of that in 1982. However, there was no signifierence between the years in intercepted photosynthetically active radiation by crops (ΔPAR), because of larger LAI in 1983. The efficiencies of dry matter accumulation per ΔPAR (EPAR) in 1983 were slightly larger than those in 1982 (Table 4). Tuber dry yield was correlated positively with ΔPAR (r=0.760*).
