Root box studies on the fertilizer use in mulberry field
By
Masao ITO and Noriko MATSUDA
The authors devised a root box system for the studies on the fertilizer use in mulberry field.
Based on the knowledge obtained from field research for mulberry tree culture, several topics in the fertilization problem were taken into consideration. Mulberry trees under the intensive perennial cropping condition undergo repeated treatments of ploughing, fertilization, harvesting and other field managements. Therefore, mulberry field soil must be always kept in well controlled status to maintain or increase its potential as well as productivity.
Fertilizer-soil-crop relationship was studied by the synthetic soil medium made of pearlite (porous water-holding material) and active clay holding water and nutrients.
As a container for soil medium, a root box with 50 cm width, 40 cm height and 8 cm thickness was prepared with wood and glass (or synthetic resin) plates. Glass or acryl-resin plate was used as frontispiece so as to observe the phenomena on the soil profile.
Two mulberry seedlings were planted 30 cm apart. Fertilizers were applied into the intermediate position between these seedlings. Thus, through colourless and translucent glass or resin plate, synthetic soil profile can be observed corresponding to the vertical section of soil profile cut out in the rectangular direction against mulberry tree row lines in the field. Compost was applied as bulky organic manure into the ditch below the surface layer. Inorganic fertilizers were also put into the same place as that for compost.
Two treatments were in this study:(1) inorganic fertilizers plus compost, (2) inorganic fertilizers alone. Total amounts of the nutrient elements for both treatments were equal: N 1. 0 g, P205 0.5 g and K20 0.5 g per box. Water supply was done to keep favourable moisture condition.
Culture experiment started on May 29 1963. On July 30 newly grown shoot, petioles and leaveson one of the two mulberry trees in each treatment were harvested. Aerial part of this tree was regenerated and whole organs including trunk, roots and aerial part were harvested on September 23. Another tree was grown without pre-harvesting and harvested on the same day.
Results obtained are summarized as follows.1. Glass or acryl resin plate was kept without black cover until July 30. At this time glass or resin plate was removed and pH indicator-mixed solution of methyl red and brom thymol blue-was sprayed on the synthetic soil medium. Quite different figures of pH distribution were found between the treatments. For inorganic fertilizer treatment, acid soil zone was found very wide, while for compost-applied treatment the acid zone showing red colour change was only found below the compost layer (see Plate 2). This tendency of acid zone formation was also proved by chemical analysis (Table 6, 7, 8).
2. Penetration of mulberry roots into compost layer was remarkably characteristic. Compost must have played an active role in abundant root growth (Plate 4, 6).
3. For the mulberry trees pre-harvested on July 30 very poor growth of main roots was obtained at the final harvest on September 23 (Plate 5).
4. A characteristic pattern of green algae growth was observed on the synthetic soil profile kept without black cover until July 30. This would be thought as a response to nutrient distribution in the soil medium and day-light supply through glass or resin plate (Plate 2). On the profile with inorganic fertilizers, wide zone of algae growth was observed, while the growth was observed around and below compost layer on that with inorganic fertilizers and compost.
5. Element contents in each harvested organ of mulberry trees were found relatively low as compared with mulberry trees cultured in a fertile soil (Table 4, 5). This would be due to the limited supply of fertilizers and unknown factors inherent to the synthetic soil medium.
6. Further
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