Analysis Method for Crop Rotations Based on Area Data : I. Classification of major cropping sequences with three crops

[摘要] Cropping surveys were conducted on three soil types (each point was 120 ha in area) in the central region of Tokachi district over a period of 8 years. In each point, survey maps for every year were divided to sections that had only one cropping sequence. Each section's data (area, cropping sequence, etc.) were input into a data base. Cropping sequences in the data base were divided into cropping sequences with three crops (CS3), which had twin rotation units. The observed area ratio of each CS3, which was denoted by a percentage based on the surveyed area, was determined six times. The mean value and coefficient of variation of the CS3's observed area ratio and the observed frequently of CS3 were determined from the six observed area ratios. Using the coefficient of variation, the major cropping sequences with three crops (MCS3), which were typical CS3, were classified. MCS3 consisted of only field crops, and they were observed over a large area and at a high frequency. In each surveyed point, only 10 or 12 types of MCS3 were observed, but their observed total area ratios were from 21 to 53%. Two MCS3 were observed to have the same rotation unit B→C (A→B→C and B→C→A). Therefore these MCS3 can link by overlapping the common rotation unit B→C, and the cropping sequence A→B→C→A was identified. Repeating this process, typical cropping sequences with many crops or crop rotations could be identified.

[学科分类] 农业科学（综合）

[关键词] Coefficient of variation;作物結合単位;Cropping sequence with three crops;3年作付;Major cropping sequence with three crops;出現頻度;Observed area;出現面積;Observed frequency;主要な3年作付;Rotation unit;十勝地方;Tokachi district;変動係数