By determining major components of sesquiterpenes in tubers a classification was made to purple nutsedges (Cyperus rotundus L.) growing in Japan and Taiwan as follows (Fig. 1):
(1) H-type; α-cyperone and β-selinene
(2) O-type; cyperene and cyperenone
(3) M-type; α-cyperone, β-selinene, cyperene and cyperenone
Experiments were carried out with the clonal material to show that sesquiterpenes variations are inherited and are not a result of environmental responses or different ages.
H-type was found in regions of Okinawa, Kyushu, Shikoku and Honshu of the south up Saitama prefecture, respectively. But O-type was not found in the north up Tanegashima. M-type was found in only a few locations in Southern Kyushu and Okinawa-region (Fig. 3).
There were differences between H-type and O-type in such ecological and physiological characters as tubers production, seeds production, seeds weight and locusta length (Fig. 4 and 5).

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In order to investigate the effects of soil reaction on the growth of Solidago altissima L. (tall goldenrod), a few experiments were performed as follows; the water culture with solutions adjusted with N HCl or N NaOH to pH 2.0-9.0, containing NH₄-N or NO₃-N as nitrogen sources, the soil culture with varied calcium levels, and the field survey of the soil pH where the plant grew well naturally.
The following results were obtained;
1) The plants in water culture grew well at pH 7.0-8.0 in NH₄-N series and 4.0-9.0 in NO₃-N series.
2) The analysis of the N, P, K, Ca and Mg contents on dry matter basis in plants in water culture showed that K, Ca and Mg contents increased in parallel with rising pH values; this tendency was especially apparent in NH₄-N series, and that K and Ca contents in plants fed with NO₃-N were as twice as those with NH₄-N.
3) When pH values in soil culture with varied calcium levels were raised, the growth decreased in an uncultivated sand soil while somewhat increased in a paddy clay loam.
4) The soils' pH values of various places where S. altissima L. grew naturally ranged widely from 5.2 of the fallow paddy field to 8.1 of the roadside.
5) From the above results, it was proved that S. altissima L. was one of the most adaptable plants to soil reaction.

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A completely ripened field on relatively old volcanic ash soil was not cropped for thirteen years' duration. The chemical properties of soil and weed vegetation in each year were investigated during that period.
The chemical properties of soil in the uncultivated plot deteriorated earlier than that of the cultivated one (cultivation to the depth of 25cm once a year). In both test plots the weed vegetation changed in the order, a field type weed (weed vegetation of ripened field), mixture of field type and upland type (weed vegetation of unripened field) and upland type (wild field type weed vegetation).
Change of the weed vegetation occurred after one year, after two to four years and after five years, respectively, in the uncultivated plot; and after three years, after four to seven years and after eight years, respectively, in the cultivated one. Border line values at which vegetation changed from ripened field type to unripened field type were pH (KCl) 5.00; base exchange acidity (y₁) 1.0; and saturation degree of calcium 50%. Those at which weed vegetation changed from unripened field type to wild field type were 4.40, 10.0 and 20%, respectively.

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This experiments were conducted to clarify the effects of fertilization on growth of weeds. The weeds used in this experiments were large crab-grass (Digitaria adscendens Henr.), common lamb's quarters (Chenopodium album L.), common purslane (Portulaca oleracea L.), Chufa (Cyperus microiria Steud.) and livid amaranth (Amaranthus lividus L.) which were typical upland weeds in the Kanto plain. Upland rice was used for reference.
1) Growth of fertilization plot was superior to that of non-fertilization one in plant length or main stem length, the number of tillers or branches and top dry weights at each species. The difference of growth was remarkable at the early stage of growth, and was decreased at the late stage of growth. Large crab-grass and common lamb's quarters were larger in plant length and top dry weight than upland rice of fertilization plot on and after 51-70 days after seeding at the plot of fertilization, and on and after 91 days at the plot of non-fertilization, too.
2) RGR of each species at the plot of fertilization was superior to non-fertilization plot at the period of 29-51 days after seeding, but RGR at the period of 70-91 days after seeding was reversed the results. RGR of all weeds examined at the period of 29-51 and 51-70 days after seeding was superior to upland rice at the plot of fertilization, and RGR of all weeds at the period of 51-70 and 70-91 days after seeding was superior to upland rice of fertilization plot even at the plot of non-fertilizatian.
3) The time of heading or flowering in each species delayed at the plot of non-fertilization. The delay was the most in livid amaranth, and was small in large crab-grass and common lamb's quarters.
4) The method of fertilization also affected the growth of weeds. Growth of large crab-grass, common purslane and Chufa at the inter-row was larger than that at the intra-row on the condition of band dressing, and growth at the intra-row was larger on the condition of whole layer placement of fertilizer. And especially, growth of weeds at the intra-row on the condition of whole layer placement of fertilizer was excellent.
5) From the resalts mentioned above, it was clear that weeds examined responded to fertilization sharply. The method of whole layer placement of fertilizer in summer season is unfavourable in aspect of weed cotrol. Weeds growing at inter-row are in need of early removal on the condition of band dressing.

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Seed production of Echinochloa spp. was examined in both rice-fields, direct-sown and transplanted with young seedlings.
(1) The heading time of each species or sub-species in Echinochloa spp. was as follows in the earlier order; Echinochloa crus-galli var. praticola, E. crus-galli var. crus-galli without awn, E. crus-galli var. crus-galli with awn, E. oryzicola, E. crus-galli var. formasensis. The variation of the period from emergence to heading was the largest with E. crus-galli var. formasensis and the smallest with E. crus-galli var. praticola.
(2) Seed number per plant of E. oryzicola was about 3, 000 grains when the plants emerged within 20 days after rice seeding and about 2, 000 grains when emerged at the transplanting time. In both cultures the seed number was less when the plants emerged later, and the seeds were not produced when the plants emerged 50 days after the rice seeding or 30 days after the rice transplanting. In the transplanting culture of young seedlings, seed number per plant of E. oryzicola was not different among plant density of 5 to 40 plants per sq. meter.
(3) A close relationship between top dry weight of E. oryzicola and seed number was found, but seed number per unit top dry weight was different according to the emerging time.

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Emergence of weeds in paddy rice dry-seeded without tillage (non-tillage plot) was compared with that in normally dry-seeded rice (tillage plot). Weed species examined included barnyardgrass (Echinochloa oryzicola Vasing.), monochoria (Monochoria vaginalis Presl.) and spike-flowered rotala (Rotala indica Koehne) as annuals, and water nutgrass (Cyperus serotinus Rottb.) and water chestnut (Eleocharis kuroguwai Ohwi) as perennials.
A large number of annual weeds in paddy rice emerged in non-tillage plot, because of higher density of seeds in surface layer of soil than in tillage plot. Emergence of barnyardgrass continued during the whole period of upland field condition, regardless of with or without tillage.
Mother shoots of water nutgrass were increased by tillage. However, in non-tillage plot, emergence of mother shoots and formation of secondary shoots occurred at the earlier time and so more quantity of water nutgrass was resulted than in tillage plot.
Emergence and growth of water chestnut were not different between tillage and non-tillage plot.

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