The Japanese pear grows abundantly in southern and western parts of Ibaraki Prefecture. In particular, the production of ‘Ko-sui’ pear is the highest in Japan.
Yields and growth rates of trees have decreased, and the amount and number of fertilizer applications have increased over the years. We investigated the plan for fertilizer application and the soil fertility of ten pear orchards in southern Ibaraki Prefecture.
The average of ‘Ko-sui’ pear tree was 28 years old, and the average of ‘Ho-sui’ pear tree was 26.5 years old in investigated orchards. The amount of fertilizer applied exceeded the recommendations in Ibaraki. Most farmers consider the soil modification function of organic fertilizer, but they do not consider its nutrient function. As a result, they apply organic fertilizer in addition to chemical fertilizer.
The pear yields were unrelated to the amount of fertilizer applied. Soil fertility also exceeded the standard of soil nutrients for pear orchards. Furthermore, the available phosphoric acid and exchangeable potassium in the soil was related to the amount of phosphoric acid and potassium applied with organic fertilizer, but inorganic nitrogen in soil was not related to the amount of nitrogen applied. This indicates that the available phosphoric acid and the exchangeable potassium were held in the soil, but the inorganic nitrogen runs off with soil water.
In order to protect the environment, nutrient recommendations in Ibaraki must indicate the presumable method of the available nutrient on organic fertilizer. We should regulate the amount of organic fertilizer applied based on the nutrient recommendation.