Studies on the evaluation of climatic productivity of paddy rice, Pt. 1, Attempt for the evaluation of climatic productivity

• Published in: Nōgyō kishō Vol. 36; no. 2; pp. 71 - 79
• Main Authors: Sugihara, Yasuyuki, Hanyu, Juro
• Format: Journal Article
• Language: Japanese
• Published: 01.01.1980
• ISSN: 0021-8588

A climatic index, Y sub(R) , which gives the potential quantity of the ripening of paddy rice, was introduced by Hanyu et al. (1966) as Y sub(R) = S sub(R) {a - b ( theta sub(R) - 21.4) super(2) }, in which S sub(R) denotes the duration of sunshine; theta sub(R) is the mean temperature during the ripening period; and a and b are the empirical constants, respectively. The authors attempted to obtain a climatic productivity index of the paddy rice by improving this index. Y sub(R) , as a linear function of S sub(R) , was modified as Y sub(R) = ln (1 + S sub(R) /M sub(0) ) {a - b ( theta sub(R) - theta sub(0) ) super(2) }, in which M sub(0) is a parameter modifying the slope of Y sub(R) increase with the increase in S sub(R) and is estimated to be 10. The constants, a and b, were estimated to be 260 and 2.70, respectively, when M sub(0) = 10 and theta sub(0) = 21.5 degrees C. Both the constants were estimated for the wide range of M sub(0) -values, and the estimated constants were introduced to obtain various M-values. The individual M, estimated by the actual yield, Y, at each area is equal to or more than M sub(0) estimated by Y sub(R) . Y sub(R) decreases with the increase in M sub(0) , even if the climatic conditions (S sub(R) , theta sub(R) ) during the ripening period are suitable. It is considered that M sub(0) is a variable that is inversely proportional to the sink capacity, receiving the photosynthetic product before and after heading, so that M sub(0) may be accepted as a growth index. The relationship between the number of grains (N) and M-values obtained by introducing a = 260 and b = 2.70 is indicated. The limiting curve was named M sub(N) . The air temperatures prior to heading time, theta sub(V) and theta sub(H) , were related to M. The lower limiting curves show the minimum values of M, M sub(V) , and M sub(H) . The larger value between M sub(V) and M sub(H) was selected as M sub(G) . M sub(G) was named the climatic index of growth. The minimum value of M sub(G) is M sub(0) (=10). Y sub(P) gives the climatic productivity, Y sub(P) = ln(1 + S sub(R) /M sub(G) ) {260 - 270( theta sub(R) - 21.5) super(2) }. Y sub(P) was named the climatic productivity index of paddy rice. From the relationship between M sub(N) and theta sub(H) , another climatic productivity index, Y' sub(P) , is given by Y' sub(P) = ln(1 + S sub(R) /M' sub(N) ){260 - 2.70 ( theta sub(R) - 21.5) super(2) }. The relationship between Y sub(P) or Y' sub(P) and the actual yield, Y, is discussed.