Improvement of Planosol Solum. Part 9: Fertilizer Distributor for Subsoil

Abstract

Abstract Based on field cultivation tests by Zhao and soil investigations by Araya, a one-to-one mixing of the second (Aw) and third (B) horizons was conducted to improve the planosol solum in China, leaving the first (Ap) horizon undisturbed by a three-stage subsoil mixing plough. This paper deals with the development of a fertilizer distributor which applies chemical fertilizers into the subsoil, where the Aw and B horizons, which are lacking in phosphorous and calcium, are mixed. Additionally, based on root density distribution of plants, this paper deals with the development of a technique in which the fertilizer is placed more densely in the upper layer than in the lower layer within the 200–600 mm depth of subsoil. The results showed that when both granular and powder fertilizers were supplied at the rear of the first or second plough body, the fertilizers reached the bottom layer with soil mixing by the plough bodies, and the fertilizer distribution density was greatest in the lower layer of the subsoil. When the fertilizers were supplied at the side of the third plough body, an improved distribution was obtained. However, the fertilizer was not distributed over the entire operating width (300 mm), but was concentrated more around the side of the third plough body. As a result, when the fertilizer was supplied both at the rear of the third plough and the side of the third plough body, the distribution sought was obtained. Here, the distribution density of the fertilizer decreased linearly with the tilled soil depth in the subsoil.