Lack of yield response in potato (Solanum tuberosum L.) to phosphate fertilizer under contrasting soil types varying in phosphate absorption coefficient and available phosphate

Abstract

There is growing evidence of excessive use of phosphate fertilizer and high residual soil phosphate levels in arable cropping systems in Japan. However, there is a lack of regional-scale information on the current status of soil-available phosphate as well as its impacts on a potato (Solanum tuberosum L.) cropping system. Although phosphorus is an essential nutrient, there have been confounding reports about the effects of excessive soil-available phosphate on potato tuber yields. This study was conducted in Hokkaido, Japan, to determine the current status of phosphate fertilizer application rate and soil-available phosphate levels, and their effects on tuber yield. In two contrasting soil types varying in phosphate absorption coefficient (PAC), soil and potato tuber samples were collected from 90 and 80 grower fields in Tokachi and Kamikawa districts, respectively, in the 2013 and 2014 growing seasons. The soil samples were analyzed for PAC, available phosphate by the Truog method, and total phosphate along with total carbon and acid-oxalate extractable aluminum. The tuber samples were collected at the harvesting stage for the calculation of yields. This study revealed (1) ongoing excessive phosphate fertilization regardless of high soil-available phosphate levels in potato-producing fields of Hokkaido, (2) no positive impacts of excess soil-available phosphate on tuber yields, and (3) no yield response from the applied phosphate fertilizer in excess of the recommended rate in two contrasting soil types. In conclusion, excess phosphate fertilizer was an unnecessary cost to the growers and could also be a potential harm to the environment, and changes are urgently needed to optimize the input-output balance of phosphate in this agricultural system.

Effects of Phosphate Fertilization Rates on Physicochemical Properties of Potato Starch

“…[ 25 ] The soils in Tokachi are derived from various volcanic ashes characterized by a relatively high phosphorus binding ability causing a relatively low phosphorus availability for plants. [ 21 ] However, if the soil is the sole determining factor, the phosphorus content in one location should be consistently either lower or higher than that in the other location regardless of the year of cultivation. The phosphorylation reaction of amylopectin is catalyzed by the α‐glucan water dikinase enzyme, of which substrates include water.…”

“…[20] In the meantime, the tuber yield showed no response to phosphate fertilization rates in the studies conducted in 170 potato grower fields in Hokkaido, Japan, indicating that reducing the phosphate fertilization rate within certain limits may have no negative impact on the tuber yield. [21] Compared to the effect of mineral nutrients such as phosphorus on crop yield, their impact on starch quality has hardly been understood. [22] In the case of cassava starch, it was reported that an increase in the phosphate fertilization rate during tuber cultivation resulted in an increased phosphorus content in the starch in association with significant changes in various physicochemical properties of the starch.…”

“…[ 20 ] In the meantime, the tuber yield showed no response to phosphate fertilization rates in the studies conducted in 170 potato grower fields in Hokkaido, Japan, indicating that reducing the phosphate fertilization rate within certain limits may have no negative impact on the tuber yield. [ 21 ]…”

Speciation and microscale distribution of phosphorus compounds accumulated in continuously fertilized greenhouse soils

“…However, compared to that in open-field farming, an intense application of phosphate fertilizer in a covered greenhouse environment results in an increased accumulation of surplus phosphorusbearing compounds (surplus-P) in the soil (Fan et al, 2020;Wang et al, 2015). Although crop yield is not affected by additional phosphate fertilization of phosphate-accumulated soils (Gondwe et al, 2017), farmers often hesitate to reduce phosphate fertilizer application. To establish adequate soil management recommendations, it is important to elucidate the chemical forms of surplus-P that determine mobility and plant availability of surplus-P. Phosphate in soil is mainly sorbed on aluminum (Al) and iron (Fe) oxide minerals, aluminosilicate clays and calcium carbonate or precipitated with Al, Fe, or calcium (Ca) (Gerard, 2016).…”