摘要:

SummarySoil samples were taken along transects cut through thickets of Rubus polyanthemos at three sites, the seeds were extracted by flotation, and the viability of filled seeds of R. polyanthemos determined by staining with tetrazolium chloride. Exotic annual species were the dominant component of the soil flora at two sites formerly undercultivation and a change in seed bank composition, both in number of individuals and numberof species, was evident from the exterior to the interior of the thickets. This was not observed in a relatively undisturbed native community. The apparent absence of suitable replacement species in the seed bank at all three sites means that they must be introduced if the sites are to be rehabilitated after the thickets are removed. Viable seeds of R. polyanthemos were present in relatively low numbers (mean 179 m−2:), so that loss of viability appears to be fairly rapi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryAdsorption of simazine (2‐chloro‐4,6‐bisethyl‐amino‐1,3,5‐triazine) was 2.2–4 times greater than that of terbacil (5‐chloro‐6‐methyl‐3‐t‐butyl‐uracil) in the same soils and adsorption of both herbicides was 2–4 times greater in the topsoils than subsoils. Adsorption was inversely correlated with herbicide movement in a thick‐layer chromatography system. One year after application of 3 kg/ha to field plots, simazine residues were highest near the soil surface, whereas terbacil residues increased with soil depth in the sandy and sandy loam soils. Total residues recovered from the upper 25 cm of soils was 5% or less of the simazine originally applied, and 10% or less of the applied terbacil. In an oat seedling bio‐assay, the GR50values were generally 1.5–3 times higher for simazine

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryEstimates of viable weed seeds in soil samples taken in 1968–1975 from 89 vegetable fields in England gave a median value of 4120 m−2in 0–15 cm.Poa annua, Stellaria mediaandMatricaria matricarioidesoccurred most frequently, and nine species accounted for 72% of all seeds found. The numbers of seeds were lower than those from a survey made a decade earlier but the species occurring most frequently were the same;M. matricarioides, however, appeared to have increased in relative impor

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryIn a field trial in 1978 at Mokwa, southern Guinea savanna zone of Nigeria, metolachlor at 1.5 and 3.0, prometryne at 2.0 and norflurazon and diuron at 1.6 kg/ha combined good weed control with high grain yield of cowpeas. The grain yields with these herbicides were comparable to those of the hoe‐weeded and significantly higher than the weedy controls. In 1979, under wetter conditions, crop injury was observed with prometryne and linuron at 2.0 kg/ha. However, the grain yields obtained with alachlor, metolachlor, chloramben, pendimethalin and norflurazon and their mixtures with prometryne, linuron, diuron or metobromuron were comparable to that of the hoe‐weeded treatment. In 1979 at Samaru, northern Guinea savanna, pendimethalin at 1.5, metolachlor at 3.0 and chlorbromuron and linuron at 1.0 kg/ha gave selective weed control. Prometryne at 2.0 kg/ha was the only herbicide that gave a significantly lower broad‐leaved weed weight than the weedy check but it reduced the crop stand. At 1.0 kg/ha it was tolerated by the crop but failed to control grasses. Metolachlor at 1.5 kg/ha had a significantly higher broad‐leaved weed weight than the weedy check. All theherbicides, except pendimethalin at 3.0 kg/ha, controlled the annual sedges at

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryIn trials carried out in 1978–80, blackgrass populations in winter wheat growing on heavy soil were substantially reduced by all chemical treatments tested, the least effective being methabenzthiazuron. Wild oat populations were also reduced by all treatments except chlofop‐isobutyl and methabenzthiazuron. On average of the 3 years only metoxuron treatment gave wheat yields significantly higher than the unsprayed c

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryThe herbicide safenerN‐dichloroacetyl‐1‐oxa‐4‐aza‐spiro‐4,5‐decane (AD‐67) is of similar efficiency as the extensively usedN.N‐diallyl‐2,2‐dichloroacetamide (R‐25788) and the structurally related 3‐(dichloroacetyl)‐2,2‐dimethyl‐1,3‐oxa‐zolidine (AD‐2) in reducing EPTC [S‐ethyl‐N,N‐dipropyl (thiocarhamate)] injury to maize (Zea maysL. cv. KSC 360). EPTC treatment produces growth retardation and deformities and inhibits CO2fixation. It does not reduce epicuticular lipids appreciably but affects wax arrangement on the leaf surface. When EPTC is applied together with one of these safeners, these injuries are not observed. All three safeners act similarly. Each prevents the herbicide‐induced aggregation of epicuticular wax of maize, thereby protecting the plants against the formation of areas where the underlying cuticle l

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryAfter cultivation in early April of a sandy loam soil with 9500 apparently viable seeds/m2in 0–10 cm, 295 seedlings/m2emerged of which about half survived to maturity in July. Seeds were dispersed from mid‐June to November and 136,460/m2were returned to the soil, representing a 14‐fold increase in the seed bank. Application of soil‐acting herbicides reduced the numbers of weeds and the total seed output, but that of tolerant species was increased. Maximum numbers of seeds were 59,980/m2forChenopodium album, 39,430/m2forSleltaria mediaand 37,580/m2forVeronica

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryThe reproductive strategies of two weeds,Spergula arvensisL. andPlantago majorL., were studied in relation to soil texture and moisture regime. On sandy soil, daily watering gave greatest dry wt per plant inS. arivensis, while fortnightly watering gave the greatest inP. major. InP. major, seed production was increased with increased moisture stress in sandy soil, but not in garden soil when watered fortnightly. Conversely,S. arvensisshowed a decrease in seed number with increasing moisture stress in both soil types. The reproductive effort ofS. arvensiswas much greater (26.2–63.1%) thanP. major(2.3–9.2%). There was greater emphasis on reproduction byS. arvensisunder both soil types and various moisture regimes whileP. majorwas characterized by higher allocation to vegetative structures which may confer a competitive advantage by increasing its efficiency of resource capture. Thus,S. arvensisseems to be r‐selected andP. majorK‐selected. The differences in the reproductive strategies of the two weeds are discussed with reference to the environmental conditions under which they grow in

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryEffect of salt stress on structural changes, ion uptake, rate of photosynthesis and path of carbon in the exotic weedParthenium hysterophorushave been investigated. Photosynthetic leaf area, chlorophyll and carbon assimilation rates were adversely affected by salt stress. Increased Na+uptake caused decrease in K+and Ca2+absorption. Originally a C3plant,P. hysterophorusappears to form aspartate as a primary product of photosynthesis when exposed to NaCl. The stimulation of PEP carboxylase activity also occurred due to salt stress. Excessive accumulation of malate during steady state of photosynthesis was possibly due to inhibition of malic enzyme. It appears that although the plant switches over to an ‘aspartate producer’ when exposed to salt, further utilization of photosynthetically assimilated carbon is through malate. Being a weed, the plant appears to be highly adaptive to stress conditi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryTwo field experiments compared various sequences of ethofumesate, methabenzthiazuron and mecoprop, and mixtures of metamitron, ethofumesate and methabenzthiazuron for their control ofPoa annuaL. andStelluria media(L). Vill. during the establishment of autumn‐sown perennial ryegrass (Lolium perenneL.).In experiment 1 pre‐emergence treatments required a second, post‐emergence spraying to give complete control ofP. annua. Grass seedlings reappeared in early spring following ethofumesate treatment, but populations built up earlier where methabenzthiazuron had been used. The most successful treatment was ethofumesate at 1.4 kg a.i. ha−1followed by 0.7 kg a.i, ha−1in spring. Methabenzthiazuron at 0.8 kg a.i. ha−1followed by ethofumesate at 0.7 kg a.i. ha−1in December was also effective. Methabenzthiazuron at 1.6 kg a.i. ha−1damaged ryegrass but was effective as a secondary treatment at lower doses in spring. Most treatments controlledS. mediasatisfactorily, but this sometimes increased the yield ofP. annua.Metamitron greatly reduced tiller numbers ofP. annuain experiment 2, especially when sprayed with methabenzthiazuron. Only treatments which included ethofumesate controlledS. mediaadequately but there was no advantage in combining this herbicide with any other for cont

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY