Effect of potassium fertilization, phosphate fertilization, and planting density on the yield and quality of sugar beet, and its relationship to soil chemical and physical properties

1990 年に北海道十勝地方の31圃場においてカリウム,リン酸施肥, 栽植密度試験を実施した.これら３試験は同一圃場内に併設設置され, 何れも1区面積15㎡で無反復ランダム配置のプロット試験で, カリウム施肥試験は0から249 kg-K ha-1(300kg-K2O ha-1) 間の7水準, リン酸施肥試験は0 から273kg-P ha-1(625kg-P2O5ha-1)間の6水準, 栽植密度試験は50000本から90000本ha-1間の7水準である. これら施肥や栽植密度の変動がテンサイの収量や品質に及ぼす増減効果を数値化するために, 圃場別にカリウム施肥量, リン酸施肥量, 栽植密度をそれぞれパラメーター(x),各テンサイ形質を目的変数(y)として直線回帰係数を算出した. さらにこれら回帰係数と土壌分析値の相関を求め, 圃場による変動の違いと土壌分析値の関連を検討した. 根重および糖量ではカリウムおよびリン施肥の回帰係数といくつかの土壌分析項目で有意な相関が認められ, これら有意な相関全てで正負が逆転していた. またカリウムおよびリン酸施肥回帰係数相互間に有意な負相関関係が見いだされた. そこで「A群：カリウム施肥効果が高くリン酸施肥効果の低い圃場」「B群：カリウム施肥効果は低いが,リン酸施肥効果の高い圃場」「C群：カリウム施肥,リン酸施肥共に効果の高い圃場」の３群の存在が考えられた. カリウムおよびリン酸施肥の糖量回帰係数を特性値として階層型クラスター分析を実施した. さらに圃場が何れの施肥反応群に属するかを土壌分析値を用いて予測する手法の検討を行ない, 正準判別で土壌分析値よりA, B, C各群の判別を行い,グラフ上に糖量のカリウムおよびリン酸施肥効果推定値をプロットするEXCELプロトタイプシートを作成した. 本モデルはテンサイの圃場試験から導き出された圃場判別モデルであるが,圃場のカリウム,リン酸肥効特性を推測する上で一助になるのではないかと思われる.Potassium and phosphoric acid fertilization and planting density analyses were conducted across 31 fields in Tokachi District, Hokkaido in 1990. Three test plots were arranged side-by-side in the same field, each with an area of 15 m2 and designed fully randomized method, with no repetition. Seven levels of potassium fertilization [range, 0–249 kg–K ha-1 (0–300kg–K2O ha-1)], six levels of phosphoric acid fertilization [0–273kg–P ha-1(0–625kg–P2O5ha-1)], and planting density [50000–90000 plants ha-1] were examined. To quantify the effect of fertilization and planting density on the yield and quality of sugar beet, these factors were varied, and linear regression coefficients were calculated for each studied field. Next, the correlation between these regression coefficients and soil analysis values was examined. Some significant correlation was found between these variables, and these signs of significant correlations were opposite between potassium and phosphoric acid fertilizations. A negative significant correlation was found between regression coefficients of potassium and phosphoric acid fertilization effects on the root weight and sugar yield. The effect of potassium and phosphoric acid fertilization can be classified into the following three groups: group A, strong effect of potassium; group B, strong effect of phosphoric acid; and group C, strong effect of both potassium and phosphoric acid. Hierarchical cluster analysis was performed for the regression coefficients of potassium and phosphoric acid fertilization effects on the sugar yield. Therefore, we investigated a method to classify cultivation fields into the abovementioned groups using canonical discriminant analysis for soil parameters and developed a prototype for automatic calculation using Microsoft Excel. This model is a field discrimination model derived from the field test of sugar beet, but it seems to be helpful in estimating the potassium and phosphate acidic characteristics of the field