Soil chemical properties affecting soybean yield on a nationwide scale in Japan

Abstract

Wide-area surveys have been conducted on a prefectural or regional scale in Japan for revealing soil chemical properties affecting soybean yield. However, they vary by region and thus, the common chemical factors through Japan remain unclear. This study aims to identify the soil chemical properties involved in soybean yield based on field data in various prefectures throughout Japan. We collected datasets of the topsoil chemical properties and soybean yields at 228 sampling points from 16 prefectures in Japan over the period of 2015–2017. The data sampling was conducted on two fields with different yield levels, namely high- and low-yield groups, which were managed by the same cooperating farmers in each point. We regarded the two fields at each point as a pair for a pairwise comparison. The average yield of the high- and low-yield groups was 3.1 t ha−1 and 2.5 t ha−1, respectively. The p-values of the pairwise comparison results were calculated via the Wilcoxon signed rank test. The differences of the exchangeable Mg (p= 0.040), and the Mg/K (p= 0.027) and Ca/Mg (p= 0.007) ratio between the high-yield and low-yield groups were statistically significant, whereas the other variables were not significant. The exchangeable Mg and Mg/K ratio were negatively related to yield, while the Ca/Mg ratio was positively related. The results suggested that excessive Mg for K or Ca adversely affects the soybean yield. As far as we know, there have been few reports focusing on the relation between the exchangeable cation, especially for the cation balance, and soybean yield. Our results may help researchers and producers deepen their understanding of the relationship between soil chemical properties and soybean yield.