The effect of silicic materials application to cerrado oxisol on field crops in the middle-west region of Brasil

This study is a technical cooperation between JICA / Japan and EMBRAPA / Brasil on the project of developing sustainable agriculture of Cerrados for management and conservation of natural resources. One of the soil genetic characteristics of Cerrado Oxisol is that the amorphous-silica content of the soil is very low. Silica is known as an essential element for rice plants and is effective in controlling rice blasts. It has also been expected to function positively for mechanical strength of plant tissues with some plants. However, there hasn't been much data collected on the silicate application to Cerrado Oxisols in relation to crop productivity. In this study, we carried out a survey on the available silica content of main Cerrado soils and an investigation on the effect of silicic materials application to plant growth by pot experiments and field examination. The result has been obtained as follows : 1) In the result of the soil survey in Planaltina-DF (CPAC) and Pedro Afonso-TO, the available silica (Si) content of the soil was Latossolo (10 - 40 mg kg**-1) < Glei pouco-humico (40 - 60 mg kg**-1) < Glei humico (50 - 120 mg kg**-1), and silica content has been increased in the order from low humic soils such as Red-Yellow soils to high humic soils such as black soils. 2) In the result of the general pot experiment (using Latossolo) on the effect of silicic materials application by using 2 kinds of silicate calcium (Japan), nickel steel sludge (Brasil) and diatomaceous soil (Brasil) for corn, soybean and rice, roots of plants from each management soil increased in proportion to application quantities of each material. In the result of particular pot experiment with root-split (using Latossolo), roots of plants in each compartment also increased in proportion to application quantities of each material and it was considered that the root property had to expand selectively into the soil with high silica content. Furthermore, the silica (Si) density of the plant had increased in proportion to application quantities of silica materials, and the dry matter of plants also had increased. From these results, it was guessed that the effect of silica application was large on field crops growth. 3) In the field examination on Latossolo, we investigated the effect of 3,000 kg ha**-1 of powdery nickel steel sludge applied at one time primarily for annual crops (corn and millet). The grain yield of corn had been increased by 5% by applying silicic material. This rate of yield increase was not worthwhile as a primary outcome, but it is certain that the quantity of roots had been increased and insect damage had been decreased by a single application. The silica (Si) density of plant (leaf + stalk) after applying silica was kept at a high level until the fruition stage compared to no application, and from this result, it was guessed that this situation was one factor in the decreased insect damage. The yield of millet planted secondary also showed the same tendency. From these results, it can be seen that there were certainly effects from silica application for field crops.