Hozumi Yoshida

Chemical characterization of conducive and suppressive soils for potato scab in Hokkaido, Japan

Absract Potato common scab induced by Streptomyces scabies is a serious constraint for potato-producing farmers and the incidence of potato scab depends on the soil chemical properties. We examined the chemical characteristics of conducive and suppressive soils to potato common scab with reference to the chemical properties of nonallophanic Andosols, recently incorporated into the classification system of cultivated soils in Japan. Allophanic Andosols with a ratio of pyrophosphate-extractable aluminum (Alp) to oxalate-extractable aluminum (Alo) of less than 0.3–0.4 were “conducive” soils with a high allophane content of more than 3%. On the other hand, nonallophanic Andosols with a Alp/Ala ratio higher than this critical value were “suppressive” soils, and their allophane content was less than 2%. The concentration of water-soluble aluminum (AI) was also a useful index for separating conducive from suppressive soils as well as the Alp/Ala value and allophane content. The suppressive soils showed a much hi...

Effect of long-term phosphorus fertilization on soil Se and transfer of soil Se to crops in northern Japan

Phosphorus (P) fertilizer can potentially serve as a source for Se accumulation in croplands. Furthermore, it has been reported that the addition of P fertilizer to soil may enhance Se availability. Japanese agricultural soils are typically enriched in P as a result of long-term, excessive P fertilization. Therefore, we conducted a three-year field experiment in order to evaluate the effect of P fertilization on the Se content of soils and crops. Potato, wheat and barley were cultivated with and without P fertilization at two field sites in Hokkaido (northern Japan) with different levels of historical P accumulation. The first field site consisted of an Andosol soil with low available P and the second site, a Cambisol soil with high available P. The three years of continuous P fertilization over the course of the experiment did not result in a significant increase in the Se content of soils or plants. The Se content of soils and plants, however, was higher in soil samples from the Cambisol field site than from the Andosol field site, and total soil Se was significantly correlated with available soil P. Soluble soil Se and the soil-plant transfer factor for Se were not affected by P fertilization. Thus, we concluded that the higher plant Se content at the Cambisol field site was primarily due to the higher levels of accumulated Se in the soil at the site and that historical excess P fertilization typical of agricultural soils in Japan contributes to increased Se uptake by crops.

Effects of Soil Type, Vertical Root Distribution and Precipitation on Grain Yield of Winter Wheat

Abstract In Abashiri in eastern Hokkaido, Japan, grain yields of winter wheat (Triticum aestivum L. cv. Hokushin) in the western area, with umbric andosol or dystric cambisol soil types, are lower and unstable compared to those in the eastern area, with mostly haplic andosol soil type. The aim of this study was to evaluate yield differences between the eastern and western areas. The vertical root distribution of wheat plants was examined over two seasons in farmers’ fields in both areas by a wall profile method. Plants grown in the western area had shallower root systems than those grown in the eastern area. Poor soil porosity and high soil penetration resistance suppressed the vertical distribution of root systems in umbric andosol and dystric cambisol. Grain yields were not always correlated with the amount and distribution of the root system. Grain yield in the 2004/2005 season was not correlated with root depth index, whereas it was positively correlated in the 2005/2006 season. During the period from heading to maturity (mid June to late July) over the two seasons, grain yield was associated with precipitation more than with temperature and total solar radiation. In the 2005/2006 season, during the late growing stage of wheat, precipitation was extremely low and soils were very dry. The difference in grain yield between the eastern and western areas was significant and negatively related to precipitation during the period from heading to maturity. Significant correlations of yield with sunshine duration and solar radiation from the heading stage to maturity were observed only on haplic andosol. The results suggest that the major factor controlling yearly changes in the difference in grain yield of winter wheat between the eastern and western areas is the difference in photosynthetic ability, which is based on rooting depth and water supply in response to solar radiation during the late growing stage.

Efficacy of single application ammonium sulfate in suppressing potato common scab.

Abstract The objective of this study was to suppress potato common scab by lowering the soil pH and increasing the concentration of water-soluble aluminum (Al) in soil with a single application of ammonium sulfate into each row. Superphosphate (P) and potassium sulfate (K) were applied to the surface soil horizon and ammonium sulfate (N) was applied only into the rows along which potato plants were to be planted. By this application method, the soil pH was lowered and the concentration of water-soluble Al was increased in the soil of the rows where potato tubers were grown. Potato common scab was suppressed in the soil containing water-soluble Al in concentrations of 0.2 to 0.3 mg L−1 or higher. The pH of the soil fertilized as indicated above remained lower than that of the control soil to which the mixture of N, P, and K was uniformly applied. In soil types such as Haplic Andosols containing allophane at high concentrations of 71 g kg−1 in Memanbetsu, the suppression of potato common scab by this single application of ammonium sulfate was less effective due to the low soluble Al concentration. In other soil types, the soil pH was easily controlled and common scab was suppressed by this method. The advantages of this method are that (a) it minimizes the use of fertilizers, thus reducing the adverse effects of unnecessary fertilizers on the soil; and (b) it lowers the cost by eliminating additional agricultural chemicals and extra fertilizers.

Effects of deep plowing and “cutting and banking” practice on the concentration of water-soluble aluminum and allophane content in Andosols: Implication for recent incidence of potato common scab in Abashiri area

Abstract In relation to the recent incidence of potato common scab (Streptomyces scabies) in Abashiri, Hokkaido, Japan, the changes in selected soil chemical properties associated with deep plowing or “cutting and banking” practice were examined. The water-soluble aluminum concentration of the 1:10 (soil: water) extract (water-soluble Al) in the Andosol virgin fields was about 0.3 mg L-1 in the A horizon, but about 0.05 mg L-1 in the B horizon. In the fields currently cultivated, where the A and B horizons had been mixed by deep plowing or by leveling of the field by “cutting and banking” practice, the concentration of water soluble Al was intermediate between that of the two horizons (about 0.08 mg L-1). The allophane content was 2.4 times higher in the Ap horizon than in the A horizon of virgin fields. The concentration of water-soluble Al in the andosol in the A or B horizon showed a hyperbolical correlation with the allophane content. It was concluded that the allophanic B horizon was mixed with the p...

Effect of fertilization on suppression of common scab of potato

Allophanic Andosols was treated in the field with different types of methods of fertilizer application in an effort to improve field suppression of common scab of potato caused by Streptomyces scabies. When superphosphate and potassium sulfate were broadcast and mixed with the surface soil, the scab severity index significantly decreased. Then, aluminum concentration in the water extracted solutions in soils were higher than 0.3 mgL-1.