Agriculture and Science 2025/04

Suppression of Germination Defects in Japanese Pear
　　　　　　　　Development of fertilizer application systems aimed at

Fruit Tree Research Center, Shizuoka Prefectural Institute of Agriculture and Forestry
Department of Fruit Processing Technology
　Ryusuke Ishikawa, Senior Researcher

Introduction

　In recent years, inconsistent flowering of Japanese pear (Prunus mume) due to poor spring germination has been occurring frequently, and has become a problem in Shizuoka Prefecture as well. This germination failure is caused by high temperatures from fall to winter, which do not increase the freezing resistance of the tree, and the tree suffers from frost damage when the temperature drops. It has also been shown that nitrogen fertilization in autumn increases the nitrogen content of flower buds, which prevents the increase in freezing tolerance and contributes to poor germination (Matsumoto et al., 2010; Sakamoto et al., 2017).
　Koshigae et al. (2022) confirmed that fertilizer application in spring reduced the occurrence of germination defects and had no effect on fruit quality.
　This study investigated the effects of a conventional fertilizer system and a fertilizer system without fall fertilization (October) on the occurrence of poor germination, fruit quality, and soil nitrogen content in Shizuoka Prefecture.

2. materials and methods

(1) Test material and cultivation management

　Twelve-year-old Japanese pear 'Kosui' (as of 2022), planted in the garden of this research center in Shimizu-ku, Shizuoka City, Shizuoka Prefecture, was used for the tests.
The vigor of 'Kosui' was slightly weak, and it was trained with two main branches on a flat trellis. Fruits were picked at 20 cm intervals at the end of finishing picking.
　The soil was yellow soil with poor drainage and soil physical properties were considered poor. In addition, 2 t/10a of cattle manure was applied annually to the test site to improve soil fertility, and cattle manure was also applied to all treatments during the study period.
　Pest control was conducted according to the pear cultivation calendar published by the Shizuoka Prefecture Deciduous Fruit Tree Promotion Association.

(2) Fertilization method

　In this study, three areas were set up for twice-yearly fertilization (September and March), once-yearly fertilization (March), and conventional fertilization (September, October, and March), with three trees in each area as test trees.
　In the twice-yearly fertilizer application, organic chemical No. 10 was used in September, and Super Ecolong 100 type, LPS 40 type, and Pear blended No. 1 were used in March, with an annual nitrogen component fertilizer rate of 5 kg/10a in September and 15 kg/10a in March (Tables 1 and 2).
　In the once-a-year fertilizer application, Super Ecolong 140 type, LPS 40 type, and Pear Compound No. 1 were used in March, and the annual nitrogen component fertilizer rate was 20 kg/10a (Tables 1 and 2).
　In the conventional fertilizer application area, organic compound No. 10 was used in September, pear compound No. 1 in October, and fruit tree compound No. 2 in March, and the annual nitrogen component fertilization was 5 kg/10a in September, 10 kg/10a in October, and 5 kg/10a in March (Tables 1 and 2).
　In the twice-annual and once-annual fertilizer treatments, phosphoric acid and potassium sulfate were applied to supplement phosphoric acid and potassium (Table 2).
　The fertilizer was applied manually to the inside of the canopy.

(3) Evaluation of the degree of germination failure

　The study was replicated with three trees per site, and three long-fruited branches (current year branches with 8 to 15 axillary flower buds) were collected from each tree every month from November to March 2022.
　The collected long-fruited branches were pre-cooled at 0°C for 3 hours and then frozen at -5°C for 16 hours. After this treatment, long-fruited branches were thawed at 0°C for 3 hours and at 5°C for 5 hours, and stored in water cuttings in a room set at 20°C.
　The survey was conducted two weeks after thawing treatment, and flower bud death was evaluated as "dead buds that have stopped growing," "buds that are likely to die in the future due to internal browning," and "buds with a portion of small flowers dead after budding" (Figure 1), and the percentage of flower bud death among all flower buds was calculated. The results of the survey were subjected to analysis of variance, and Tukey's multiple comparison test was performed for months in which there were significant differences.

(4) Evaluation of impact on flowering

　The survey was repeated with three trees in each test plot. Ten long-fruiting branches were randomly selected from each tree, and the flowering of axillary flower buds was confirmed over time. Flowering was confirmed in clusters (flower buds), and the flowering date of a cluster was defined as the time when the first flower of the cluster flowered.

(5) Determination of inorganic nitrogen in soil

　Soil samples were collected from three points in each test plot and inorganic nitrogen content was measured. Measurements were taken monthly from September 2022 to March 2023. The measured values for each treatment were subjected to monthly analysis of variance, and Tukey's multiple comparison test was performed for months in which there were significant differences.

(6) Determination of nitrogen content of flower buds

　The survey was repeated with three trees in each test plot, and three shoots were randomly selected from each tree to measure nitrogen content. Measurements were taken monthly from November to March 2022. Measurements for each treatment were analyzed for variance on a monthly basis.

(7) Evaluation of fruit quality

　The survey was repeated with three trees per test plot, and the yield (kg/m2 ) per unit canopy area (1 m2 ) and average fruit weight were calculated for each tree. Ten fruits were collected from each tree, and sugar content, pH, and fruit hardness were measured.
　For sugar content and pH, about 1/8 of the fruit was pressed using a manual juicer, and the juice was examined using a pocket sugar meter PAL-1 (ATAGO Co., Ltd.) and a pen-type pH meter SK-670PH (Sato Measuring Instrument Manufacturing Co., Ltd.). Fruit hardness was measured by cutting the fruit in half lengthwise and examining two points at the equator using a fruit hardness tester FT011 (Fujihira Kogyo Co., Ltd.).
　Measurements for each treatment were subjected to analysis of variance.

3. results

(1) Influence of different fertilization methods on the degree of germination failure

Table 3 shows the percentage of flower bud failure in 'Kosui'. However, no significant difference was observed for long branches collected in November, December, and February.

(2) Effect of different fertilization methods on flowering

　Average temperatures from November 2022 to April 2023 remained above normal overall, although they were sometimes below normal from mid-December to early February (Figure 2).
　The time to reach a flowering rate of 20% to 80% was about 3 days in the biannual and annual fertilizer treatments, and about 5 days in the conventional fertilizer treatment (Figure 3).
　No death of flower buds was observed in all the plots (data omitted).

(3) Changes in the amount of inorganic nitrogen in soil due to different fertilizer application

The amount of inorganic nitrogen in the soil was significantly higher in November and December in the conventionally fertilized area than in the twice- and once-annual fertilized area (Figure 4).

(4) Effect of different fertilizer application on nitrogen content of flower buds

　Nitrogen content of flower buds did not differ significantly among all treatment months (Table 4).

(5) Effect of different fertilizer application on fruit quality

　There were no significant differences in fruit quality at different fertilizer application times (Table 5).

Summary

　In Japanese pear, it has been shown that the method of applying fertilizer once in spring is effective as a measure to reduce the occurrence of germination failure due to frost damage (Koshigae et al., 2022).
　Currently, the incidence of poor germination of Japanese pear in this prefecture is less than in western Japan, but it is likely to increase in the future because of the trend toward higher temperatures in autumn and winter every year.
　In this study, we investigated the effects of twice-yearly (September and March) and once-yearly (March) application of fertilizer on Japanese pear 'Kosui'. The results showed that the incidence of poor germination was lower (Table 3) and the variation in flowering was less (Figure 3). Fruit quality in the twice-annual and once-annual fertilizer application areas did not differ from that in the conventional fertilizer application area, indicating that a change in fertilizer application timing had no effect on fruit quality.　Furthermore, the amount of inorganic nitrogen in the soil in the fall and winter, which is the cause of reduced freezing resistance, was lower in the twice-annual and once-annual fertilizer application areas than in the conventional fertilizer application area, suggesting that the change in fertilizer application timing can suppress the occurrence of germination defects.
　These results suggest that a fertilizer system without autumn fertilization (October) is effective in reducing germination defects of Japanese pear 'Kosui' in this prefecture.

5. cited references

Matsumoto K., Kato M., Takemura K., Tanabe K., Tamura F. (2010) Autumn nitrogen fertilization rate of Japanese pear.
　Effects on cold tolerance and lipid content. Journal of Park Science and Technology. 9(3): 339-344.
Sakamoto, D.,K. Fujikawa, T. Sakaue, H. Inoue,A. Ito, T.Moriguchi, A, Higashi and T. Sugiura.(2017)Application of livestock waste compostas a source of of nitrogen supplementation during the fall-winter season cause dead flower buds in Japanese pear 'Kosui' Hort.
Koshigae, Daichi; Sakaue, Hiromi; Sakamoto, Daisuke; Sugiura, Hiroyoshi; Kizaki, Kenya; Uchino, Koji; Sugiura, Toshihiko (2022) Revision of fertilizer application timing
　Verification of technology to reduce germination defects of Japanese pear cultivated in the open field by the good germination. Journal of Orchard Science 21(4): 433-440.

No Soil - Vol. 40 (Final)
　　Aging of our nation's farmers is a cause of concern for food production
　　　-The key to stopping the aging of the population is to support newcomers.

Former Technical Advisor, Hokkaido Branch, Jcam Agri Co.
Teruo Matsunaka

　This is the final article in this series. I would like to take a short break from the soil to discuss the possibility of Japanese agriculture becoming "senile" and the key to overcoming this situation is to support and promote the entry of young people into the agricultural industry.

1. less than 1% of the population is engaged in key agricultural activities

　Japan's population grew rapidly during the period of high economic growth (from 1955 to around 1973) (Figure 1-above). The population continued to increase until 2010, when it peaked at 128 million and then began to decline. However, the number of people who are engaged in agriculture on a daily basis (core farmers, hereafter abbreviated as "core farmers") has been declining since then. However, the number of people who are engaged in agriculture on a daily basis (key farmers, hereafter abbreviated as "core farmers") has been declining since 1960. This was especially remarkable during the period of rapid economic growth, when the population grew rapidly. In 1960, the number of key farmers was 11.75 million (12.6% of the population), but by 1975, the number had dropped to 4.89 million (4.4% of the population) (Figure 1-above). In terms of population, the number of residents in 1975 was one-third of that in 1960.
　It is clear that people moved from agriculture to industry during this period. At the same time, this period coincided with a sharp decline of more than 20% in Japan's food self-sufficiency ratio (on a calorie basis), from 79% in 1960 to 54% in 1975. This was the result of importing agricultural products and exporting industrial products to promote economic growth.
　The declining trend of key farmers has not changed since then, and by 2024 there were 1.11 million people, only 9% of the 1960 figure, and less than 1% of the population (Figure 1-above).

2. aging of key farmers

　Our country's population is aging at an accelerating rate. Key farmers are no exception. The percentage of key farmers aged 60 years or older in the key farmers has been declining and aging at the same time, reaching 80% in 2024, compared to 14% in 1960 (Figure 1-bottom).
　The most recent change from 2020 to 2012 is particularly interesting. Unlike in the pre-2020 period, the percentage of those aged 60 and over stagnated for the past four years (Figure 1-bottom). On the other hand, the percentage of those aged 70 and over increased significantly during this period, and the percentage of those aged 75 and over also increased more than before. This fact indicates that the aging of the farming population progressed without sufficient replenishment of key farmers under the age of 60. Whether this is simply a temporary phenomenon or whether this trend will persist remains to be seen.
　The average age of key farmers has increased consistently from 59.6 years in 1995, the year for which data are available, to 69.2 years in 2024. At this rate, there is a possibility that our country's agriculture industry will cease to function due to "senility" in less than 30 years.

3. the downward trend in the number of new farmers continues unabated

　The only way to prevent the "decline" of Japanese agriculture is to increase the number of young farmers entering the farming industry. However, the number of new farmers has decreased by half from 81,000 in 2006 to 43,500 in 2011 (Figure 2). However, since the number of key farmers has also decreased, the ratio of new farmers to key farmers has not changed significantly since 2003, remaining within 3.8% (Figure 2).
　New farmers are classified into the following three categories. Newly self-employed farmers (i.e., household members of private farmers whose main occupation during the year prior to the survey was self-employment in agriculture. The three categories are: (1) new self-employed farmers (household members of individual farmers whose main occupation during the year prior to the survey was self-employment; (2) new employed farmers (those who were newly employed by a corporation as a regular employee and engaged in farming during the year prior to the survey), and (3) new entrants (those who independently procured land and funds and started farming during the year prior to the survey).
　The majority of new farmers are new self-employed farmers (Figure 2). New self-employed farmers can be regarded as farmers who have inherited the farm from their parents. The percentage of new self-employed farmers aged 50 or older remained almost unchanged from 77% in 2007 to 79% in 2011 (Figure 3). Although the parents of key farmers are aging, there has been no significant change in the timing of business transfers to their children. In the first place, the number of key farmers themselves is decreasing, and the number of new self-employed farmers who succeed them is not on the increase (Figure 2). Moreover, the number of new self-employed farmers, most of whom are over 50 years old, has not stopped the aging of the key farmers.

4. very few new entrants

　On the other hand, a relatively large proportion of new entrants to farming are young people (49 years old or younger) (Figure 3). Since 2012, the percentage of young farmers among new entrants has remained high at around 70%. Therefore, in order to stop the aging of key farmers, it is essential to increase the number of new entrants. However, the number of new entrants has increased from 2.2 thousand in 2006 to only 3.8 thousand in 2011 (Figure 2). This represents only 0.1-0.3% of the key farmers. This will not even slow the aging of key farmers. Why are there not more new entrants to the farming industry?

5. barriers to new entrants - financial and farmland issues

　There are young people from the city who are not familiar with agriculture, but who yearn to become farmers. I have come in contact with many such young people. However, when they started farming, they had to face difficulties in raising funds and acquiring farmland.
　Various support measures (e.g., funds for starting business, funds for young farmers, and business development support programs) are available from the national and local governments. However, there are conditions for approval to receive these funds, and in reality, it is not easy to procure funds. It is necessary to ease the requirements for receiving these funds to make it easier for newcomers to obtain loans and subsidies.
　Agricultural land is the foundation of national food production and is valuable social capital. Therefore, the Agricultural Land Law has been enacted to properly preserve agricultural land. To acquire farmland, farmers must meet the requirements for acquisition and obtain permission from the Board of Agriculture. The major issue in actual acquisition is the price of the land. The price of farmland in Japan is 7 to 30 times higher than in Western countries (MAFF, 2010).
　The young people who have passed through these difficulties and made their dreams come true are the ones who will lead the rejuvenation of our country's key farmers. Their support is extremely important.

thanks

　I would like to express my sincere gratitude to all the readers who have enjoyed reading this series of articles over the past four years. I would also like to express my deepest gratitude to all those who carefully reviewed my manuscripts and to the editorial staff who encouraged me in my writing. Thank you very much.