Bulletin of The Iwate Agricultural Research Center No.8
Summary

Studies on Winter-seeding Cultivation of Winter Wheat
Kengo OGIUCHI
@In wheat cultivation by usual autumn-seeding cultivation in Iwate Prefecture, the work for wheat sowing overlaps with the harvesting of the summer crop such as rice, and this is a big problem for the farmers. In the drained paddy field after rice cultivation, it is not possible to seed wheat at the proper time because the plowing work is difficult due to rain in autumn and the insufficient drain measures. In this study, the technology of winter-seeding cultivation, seeding winter wheat before the continuous snow cover, was developed to solve these problems. The overwintering ability of winter wheat seeded before the continuous snow cover was investigated, and a suitable variety and the best seeding method for winter-seeding cultivation were determined. Then, I developed a suitable method of nitrogen fertilizer application to obtain a high grain yield and high grain quality, and a disease and weed control system for winter-seeding cultivation. Moreover, I found that the winter-seeding cultivation was effective in reducing the disease incidence of wheat yellow mosaic. I found that the processing quality in winter-seeding cultivation was the same or better than that in standard autumn-seeding cultivation. The results obtained are as follows.

1. A selection of a suitable variety and the best seeding method for winter-seeding cultivation
@Winter wheat varieties with different resistance to cold and snow were seeded before continuous snow cover. It will be difficult for a variety, which has low resistance to cold and snow, to pass the winter, and the winter wheat cultivar "Nanbukomugi" with strong cold and snow resistance will be suitable for winter-seeding cultivation. Because the seedlings emerged before the continuous snow cover are seriously damaged by frost, the seeding date may be the day when the accumulative mean temperature above 0Ž before the beginning of continuous snow cover is 95Ž or less in normal years. It is early to late December in Iwate Prefecture. The increase in seeding density is indispensable to secure stable grain yield in winter-wheat cultivation because the top growth is reduced and the number of ears decreased by delaying the seeding time. I consider that the optimum seeding density in winter-seeding cultivation is 350 grains/m
2.

2. Method of fertilizer application in winter-seeding cultivation
@In the plants supplied with N fertilizer at seeding time, the growth at maturity and yield were higher than in those supplied with N just after the snow melted. This is probably because early growth was promoted by a sufficient amount of N released from the fertilizer applied at seeding time. In the plants supplied with 10g/m
2 N as a basal dressing, lodging was not observed, and the grain yield was as high as or higher than that in standard autumn-seeding cultivation. The grain yield with an increased amount of N fertilizer was higher in the upland field than in the drained paddy field. This is probably because tillering in the upland field was promoted by N absorbed before the heading stage, which was larger in the upland field than in the drained paddy field. In the drained paddy field, the protein content of the grain was lower than that in the upland field, and increased little even by increased basal dressing, but markedly increased by the N top-dressing at full heading time. I consider that this difference between fields was caused by the difference of the time and amount of soil N mineralization. It is necessary to control the protein content of the grain by the N top-dressing at full heading time depending on the usage of the grains. The grains grown in the upland field are suitable for making bread because the protein content was high, and the recommended amount of application of N top-dressing at full heading time is 2 g/m2 because the protein content of the grain in the non- top-dressed plants was occasionally below the target value. In the drained paddy field, it is necessary to increase the protein content of the grain by N top-dressing for making both Japanese noodles and bread, and the application of N top-dressing at full heading time at 2 g/m2 should be suitable for making Japanese noodles and 4g/m2 for making bread.

3. Disease control and weed control in winter-seeding cultivation
@Under non-controlled conditions, the incidence of powdery mildew and leaf rust was higher in winter-seeding cultivation than in standard autumn-seeding cultivation. This is probably because the amounts of fertilizer and the top growth were different between winter-seeding cultivation and standard autumn-seeding cultivation. No significant difference was observed in the incidence of scab between winter-seeding cultivation and standard autumn-seeding cultivation, and the difference in precipitation from the heading time to the flowering time was considered to influence the incidence of scab greatly. The standard method of disease control can be applied because it significantly inhibited all diseases in winter-seeding cultivation. Fungicide spraying for multiple times, that is, at the flag leaf time and the flowering time (and 7 days after the flowering time in the case of much rain after the flowering time) was suitable for control of these diseases in winter-seeding cultivation. In winter-seeding cultivation, herbicide spray in the growing time efficiently inhibited the growth of the weed. The use of thifensulfulon-methyl to control weed in winter-seeding cultivation is recommended because the grass weed occurred in the drained paddy field more frequently than in the upland field. In winter-seeding cultivation, a single application of herbicide spray inhibited the occurrence of weed as much as in standard autumn-seeding cultivation, but it is necessary to consider the combination of herbicides and the frequency of herbicide spraying depending on the occurrence of weeds in the field.

4. Evasion from wheat yellow mosaic by winter-seeding cultivation
@Wheat yellow mosaic is a soil-borne virus disease, and the disease incidence is decreased by delaying the seeding time. Thus, the seeding before continuous snow cover is expected to reduce the incidence of wheat yellow mosaic. In fact, the field with standard autumn-seeding cultivation was highly infested with wheat yellow mosaic virus (WYMV)(the disease incidence was 100“), but in the field with winter-seeding cultivation, the disease incidence was 0 or very low. The incidence of wheat yellow mosaic was suppressed by low temperature after seeding, which was below 5Ž from seeding date to late March. In standard autumn-seeding cultivation, the incidence of wheat yellow mosaic varied with the field, but the difference was no longer found under continuous cropping. In winter-seeding cultivation, the incidence of wheat yellow mosaic was not observed in any field, even when wheat was cropped continuously. In winter-seeding cultivation, the number of ears was larger, the thousand-grain weight was heavier, and the yield was higher than in standard autumn-seeding cultivation. In standard autumn-seeding cultivation, the severity of wheat yellow mosaic was decreased and the yield increased by chemical control with TPN, but the effect varied with the year. However, even in the plot with dusted TPN, the disease incidence was higher than in winter-seeding cultivation, and the incidence in the next cropping did not decrease. Moreover, winter-seeding cultivation was more economical than chemical control with TPN. Therefore, I consider that winter-seeding cultivation is more effective for wheat yellow mosaic than chemical control with TPN.

5. The processing quality of winter wheat grown by winter-seeding cultivation
@The processing quality (amylogram, milling, 60“ extraction flour, bread-making and noodle-making characteristics)of winter wheat cultivar "Nanbukomugi" and "Yukichikara", which were the main cultivars of Iwate Prefecture were investigated, and were compared with those of winter wheat seeded in autumn. The winter wheat in winter-seeding cultivation matured 3 ` 5 days later than that in standard autumn-seeding cultivation but can be harvested in early July before the rainy season. Thus, the harmful effect of much rain in grain quality due to the delay of maturity was avoided in winter-seeding cultivation. In winter-seeding cultivation, the thousand grain weight was lighter, but the bulk density was the same or higher, and the milling quality, flour color and farinogram characteristics were nearly the same as in standard autumn-seeding cultivation. In winter-seeding cultivation, the ash content of the grain was lower, and the protein content of the grain was the same or higher than those in standard autumn-seeding cultivation. No significant difference was observed between winter-seeding cultivation and standard autumn-seeding cultivation in the bread-making and noodle-making characteristics, but in cultivar gYukichikara, the bread volume and total overall characteristics in winter-seeding cultivation were higher than those in standard autumn-seeding cultivation. I consider that the protein content of the grain in winter-seeding cultivation was increased by the amount of fertilizer, which was larger in winter-seeding cultivation, than in standard autumn-seeding cultivation resulting in a higher bread-making quality. Although the growing phase in winter-seeding cultivation is different from that in standard autumn-seeding cultivation, the appearance quality of the grain and the processing quality in winter-seeding cultivation were the same or better than those in standard autumn-seeding cultivation.
The ecology, root distribution and root nodule formation of Hippophae rhamnoides L.
Hiroshi OHNO, Naoshi KONNO, Koetsu KONNO, Hitoshi SASAKI and Koki KANAHAMA
@We investigated the ecology and the distribution of root systems of Hippophae rhamnoides L. cultivated in Rikuzen-takata city.
@The germination and blossom period of H. rhamnoides ssp. mongolica (Russian type) was earlier than H. rhamnoides ssp. rhamnoides (European type) about a few days. The harvest time of Russian type was earlier than European type about a month.
@Although the amount of root was high within the range of 75cm from the trunk and 25 cm from the soil surface, almost the same amount of the fine root of the diameter 5mm or less was observed in the layer of 25-50cm and 0-25cm in depth. The root nodule was not observed from the layer of depth 25cm or more, it was suggested to exist in a shallow place in the underground.
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