In this experiment, the effects of nitrogen application on the growth and seed productive structure of large crabgrass and common purslane were investigated from the same viewpoint as the previous report. Nitrogen was applied at rates of 0, 10, 50 and 100kg per 10a for each of two species of weeds.
1. The growth increments of each weed generally were promoted with the increase of nitrogen application. In common purslane, however, most characters examined, such as stem length, number of leaves, total dry weight and pyxis per plant, showed the maximum value at the 50kg level, and decreased at the 100kg level. In large crabgrass, on the other hand, total dry weight, culm length and number of heads per plant showed the maximum value at the 50kg level, and others such as number of seeds and seed weight per head and 1, 000 kernel weigth showed the maximum value at the 10kg level beyond which those decreased with the increase of nitrogen application.
2. The degrees of phenotypic plasticity obtained in several characters at vegetative and maturity stage were generally higher in large crabgrass than in common purslane, and those on number of leaves and heads per plant in large crabgrass were considerably high as compared with the other characters. On the contrary, the degree of phenotypic plasticity on 1, 000 kernel weight of both weeds was the lowest among the characters examined. From this results, it seemed that 1, 000 kernel weight was a relatively stable character to environmental stress condition.
3. Both weeds had the lowest crude reproductive efficiency (CRE) at the 0kg level, and CRE of both weeds showed a tendency to increase with the increase of nitrogen application. The maximum CRE in common purslane was 28.5% at the 100kg level, but that in large crabgrass was 25.3% at the 50kg level beyond which CRE decreased.
4. Variations between individuals within a plot, which were examined on some characters in relation with nitrogen application level, were observed clearly to increase both at the plots with excess application of nitrogen and without nitrogen.
5. Based on the results of reproductive efficiency, phenotypic plasticity and individual variations within each nitrogen level, the problems on environmental adaptation of weeds were discussed.

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1. The flower stalks of Pinellia ternata grew from May to the middle of September in Kyoto district. The highest bolting percentage was shown in June. It was recognized that the bolting percentage became higher, as the weight cf corms increased. Some more 4gr. corms, occasionally, developed more two stalks at the same time.
2. The seed setting percentage was the highest in August. The percentage which was calculated from the numbers of total stalks and total setting seeds was 15-16% in the corms from 1 to 6gr. in weight.
3. The bolting percentage was lower, as the corms were planted deeper. When the corms planted 20cm at depth, they developed no flower stalks.
4. When the numbers of seeds setting in an inflorescence were examinated in 60, it was shown that they fluctuated between 3-42 seeds, and averaged 19 seeds. One hundred seeds weight ranged from 200 to 1200mg with a mean weight of 685mg. When the germination of these seeds was investigated in July and August, the former showed 34.5% and the latter, 56.2%. No relations between seed weight and germination percentage was recognized.

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Thiocarbonyl amino acid derivatives [N-(4-chlorophenylthiocarbonyl) amino acids (PT) and N-(4-substituted benzylthiocarbonyl) amino acids (BT)] were examined on their herbicidal activities by pot tests (pre- and post-emergence application under submerged and upland conditions).
(1) Activity of PT was generally low and their activity persistence was short. In general, activity of free acid type compounds of amino acid residues was slightly inferior to that of methyl ester type compounds of the residues.
(2) Activity of BT was not associated with the kinds of amino acid residues and lower than that of PT. Activity variation which might be caused by the substituents (-Cl or -CH₃) of the para-position of the benzyl groups was not almost observed.
(3) In the both lineage compounds, PT and BT, activity owing to the modification [-COR; R=-OH, -OCH₃, -NH₂, -NHC₂H₅ or -N(C₂H₅)₂] of carboxyl groups of glycine and sarcosine residues decreased in the following order: -OCH₃≥-OH≥-N(C₂H₅)₂>-NHC₂H₅>-NH₂.
(4) In the BT (amino acid residues: glycine or sarcosine), activity order caused by substitutions at the para-position of the benzyl groups was as follows: -Cl≥-NO₂>-CH₃>-OCH₃>-H.

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N-(Substituted phenylcarbamoyl) amino acid derivatives [N-(3, 4-dichlorophenylcarbamoyl) amino acids (DA), N-(substituted phenylcarbamoyl) DL-alanines (SA), N-(3, 4-dichlorophenylcarbamoyl)-N-methyl amino acids (DMA), N-alkyl-N-(3, 4-dichlorophenylcarbamoyl)β-alanines (βDA), N-methyl-N-(substituted phenylcarbamoyl) β-alanines (βSM) and N-(3, 4-dichlorophenylcarbamoyl)-N-methyl β-alanine thiol esters (βDMT)] were examined on their herbicidal activity by the pot tests.
(1) Activity of DA was generally low and the compounds with an DL-alanine residue showed the strongest activity among DA. Difference between free acid form and methyl ester of carboxyl groups of amino acid residues was not observed. Among SA, N-(3, 4-dichlorophenylcarbamoyl) DL-alanine showed the strongest activity.
(2) Activity of DMA was generally found high. Among them, methyl esters of glycine, β-alanine and γ-aminobutyric acid showed rather potent activity. Especially, β-alanine methyl ester (MCMD) exhibited excellent margin of selectivity for wheat under the condition of foliar application.
(3) Activity of β-DA depended upon the kinds of alkyl group and changed continuously against those of the group. The compound having iso-propyl group showed the strongest activity but caused serious damage on wheat.
(4) In the methyl ester form of β-SM, activity varied in proportion to the hydrophobic constant (π) of substituents. In the free acid form of β-SM, however, activity varied in inverse proportion to π. Among β-DMT, ethyl thiol ester showed the strongest activity.

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The present authors tried to make clear a dominant species of Scirpus weeds or so-called “hotarui” in Japanese paddy rice fields.
1. Although Scirpus juncoides Roxb. var. ohwianus T. Koyama was identified in all the seed samples sent from 17 research stations in 15 prefectures, S. juncoides Roxb. var. hotarui Ohwi was not at all. S. wallichii Nees appeared from 3 seed samples. S. wallichii was also sent from Akita Prefectural Agricultural Experiment Station where this species had been separated from S. juncoides var. ohwianus. S. hondoensis Ohwi var. leiocarpus Ohwi appeared from only Hokkaido Agricultural Experiment Station. But their percentages were very low, that is, S. wallichii and S. hondoensis var. leiocarpus appeared 1-3 and 9% respectively.
2. Eleven kinds of herbicides showed excellent effects on S. juncoides var. hotarui by both pre- and post-emergence applications. By the pre-emergence application ethyl ester of MCPA, sodium salt of PCP, butachlor, benthiocarb and piperophos showed also high effects on S. juncoides var. ohwianus and S. wallichii, but only ethyl ester of MCPA and bentazon showed high effects on the above 2 species by the post-emergence application. Trifluralin had no effect on the 3 kinds of Scirpus, and both simetryne and dimethametryn had no effects on S. wallichii.
3. In consequence of our investigations on the growing place of Scirpus plants on the outskirts of Fukuchiyama city, adult plants of S. juncoides var. hotarui were recognized at only 4 non-cropping paddy fields, a balk and footpath and a non-rice transplanted area in a paddy rice field. It was growing together with short plants in swampy places. But it was never observed in rice-growing paddy field, where almost all Scirpus plants were S. juncoides var. ohwianus.
4. The noxious “hotarui” in Japanese paddy rice fields must be S. juncoides var. ohwianus.

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The ecological investigations on perennial weed, Oenanthe javanica D. C. were conducted in a paddy field of Fukuoka Prefectural Agricultural Experiment Station and various methods of cultural control were evaluated.
1) In paddy field, overwintering shoots from the stolon of Oenanthe javanica D. C. started to grow rapidly in the middle of April and the plant height and the length of stolon of the weed were approximately 12cm and 30cm respectively in the latter part of June when the puddling began.
2) The sprouting percentage of stolon was lowered when water content of the weed folliage became below 60 percent, and the sprouting viability of the stolon was entirely lost at 50 percent level.
3) Excised stem of the weed showed the highest rate of sprouting under the upland field condition of water content, whereas under the condition buried in the soil layer of 1-2cm, the sprouting rate was in the range of 60 to 90 percent. The sprouting rate, however, was greatly lowered due to the burying under the wetting soil, and no sprouting was observed in the puddled soil even in the burying degree of 1-2cm.
4) It was concluded that the highest control of Oenanthe javanica D. C. was obtained by a rather deep plowing 25 to 10 days before puddling, then burying foliage in the soil layer by puddling under shallow flooding condition.

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Some indicators indicating the stages of the maturation of farms were introduced based on soil pH (KCl) and some characteristics in quantity of the weed vegetation. It was found the following relationships existed: between the numbers of weed species per 3.3m² of farm (Y) and soil pH (X),
Y=-895.35+517.66X-97.76X²+6.09X³
between the numbers of individuals of weed (Y) and soil pH (X),
Y=-72999.64+42421.62X-8077.55X²+508.08X³
and between the weight of green weed (Y) and soil pH (X),
Y=-299.14+175.12X-33.42X²+2.10X³, respectively. However, it proved that these equations didn't necessarily agree to every cases. So in order to introduce more suitable relationships between them, the conditions determining growth of weed were divided and the equation was obtained separately: The following equations were obtained between the fresh weight of weed (Y) and soil pH (X),
(1) Y=-290.85+166.89X-30.98X²+1.89X³ and
Y=-334.75+193.62X-36.54X²+2.27X³
for years of richer and poorer in the amount of precipitation during April to July, respectively.
(2) Y=278.61-180.16X+38.89X²-2.76X³ and
Y=-218.99+121.87X-21.82X²+1.28X³
for years of higher and lower temperature during April to July.
(3) Y=621.19-379.74X+77.52X²-5.25X³ and
Y=-238.65+135.31X-24.80X²+1.49X³
for autumn cultivating and spring cultivating by plowing with a large-sized cultivator, respectively.
(4) Y=130.50-91.13X+21.30X²-1.61X³ and
Y=-90.44+44.34X-6.29X²+0.24X³
for plowing and rotary cultivation with a large-sized cultivator.
(5) Y=762.13-468.58X+95.60X²-6.45X³,
Y=-90.14+44.48X-6.37X²+0.25X³ and
Y=-364.16+206.57X-37.94X²+2.29X³ for the data obtained at mid-June, mid-July and mid-August, respectively. Using these quantitative indicators of weed population here along with the qualitative ones which had already been obtained (reported in 5th part of the same title as this), it seems to be possible to decide properly counterplans of preservation for weed.

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Rhizome fragments of Agropyron repens different in length were buried at different depths in soil and behavior of the shoots emerged from them were examined in this study.
1) The shoot emergence above ground was retarded with increasing depth.
2) The longer was the rhizome length, the shorter was the period required for the shoot emergence in the same depth.
3) The shoots reached ground level mainly by the elongation of the first and the second internodes in long rhizome fragments, while by the third and the fourth internodes also in shorter ones.
4) All shoots emerged from 5cm depth, while the shoot emergence was decreasing with increasing depth until no shoot was emerged below 25cm.

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