Land productivity map for soybeans [Glycine max], based on natural land conditions
1996
Kohyama, K. (Hokkaido National Agricultural Experiment Station, Sapporo (Japan))
Land productivity for soybeans with in the Tokachi region (Japan) was evaluated based on meteorological and soil data. Land evaluation was carried out by the following procedures: (1) collection of soybean yield data, meteorological data, and soil data; (2) estimation of ranking of soybean yield by Hayashi's quantification II; (3) calculation of evaluation indexes named "Yield" and "stability"; and (4) land evaluation based on those tow indexes. Estimation equations for the ranking of soybean yield were made using 9 factors including cumulative temperature, phosphate absorption coefficient (PAC) and so on. Meteorological factors strongly affected the estimated ranking of yield and PAC in volcanic ash soil, and humus content in lowland soil also affected the ranking. As a result of comparison between the average of estimated soybean yields and the average of actual yields for 3 years in Ikeda and Shikaoi towns, the proportion of estimation to actual value was nearly constant and variances of estimated values between years were also similar to those of the actual ones throughout the 3 years. These facts suggested that the equations fit well. The index of "yield" was the sum of ranking of soybean yield over the 3 years and was classified into 3 categories. The index of "stability" was the difference of maximum and minimum ranking of soybean yield over the 3 years and was classified into 2 categories. The following six classes of land productivity were established for soybeans by combining "yield" and "stability" indexes: high yield and stable, high yield and unstable, medium yield and stable, medium yield and unstable, low yield and stable, and low yield and unstable. Two-hundred-fifty-meter grid maps of land productivity for soybeans in Ikeda and Shikaoi towns were made using these criteria
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