Unweeded Control Research Articles

Weed control in lentil (Lens culinaris) in eastern Turkey

This study investigated the effect of 12 herbicide applications and hand weeding (once, twice, and repeated) in comparison with a weedy control on seed and total crop biomass yield of lentil (Lens culinaris) in 2000 and 2001 under the dry conditions of Erzurum (29°55'N and 41° 16'E at an altitude of 1850 m), Turkey. In both growing seasons, data were collected on the density and dry weight of weed species, density of lentil, seed yield, total crop biomass yield, and harvest index. Weed control applications significantly decreased density and dry weight of weeds and increased total crop biomass and seed yields by 49.2% (linuron plus prometryn) and 74.9% (prometryn plus fluazifop‐p‐butyl), compared with the unweeded control. Pre‐emergence plus post‐emergence combinations, however, gave no clear advantages over single applications of linuron, prometryn, and metribuzin. Metribuzin reduced plant density in wetter conditions of the second year. In conclusion, linuron and prometryn alone were effective in controlling weeds on lentils without apparent toxic effects. Hand weeding once was equally effective.

Spacing and weed management in transplanted basmati rice

A field investigation was carried out at the Instructional farm, College of Agriculture, Vellayani during 2000-2001 to assess the effect of spacing and weed management practices on the performance of basmati rice. The treatments comprised of three spacings (15x15, 20x10 and 15x10 cm) and five weed control treatments (weed free check, unweeded control, hand weeding twice at 20 and 40 DAT, anilofos+2,4-DEE (readymix) 0.40+0.53 kg ha at 6 DAT supplemented with hand weeding at 20 DAT and anilofos+2,4-DEE (readymix) 0.40+0.53 kg ha' at 6 DAT supplemented with 2,4-D sodium salt 1 kg ha at 20 DAT). Grasses were the predominant weed species observed in the experimental field. Unchecked weed competition reduced grain yield to the tune of 46%. Herbicides were most effective in controlling the weeds. The results revealed that with 20x1 Ocm spacing (50 hills m2), pre-emergence application of anilofos+2,4-DEE (readymix) 0.40+0.53 kg ha supplemented with 2,4-D sodium salt 1 kg ha¹ could result in maximum grain yield and minimum weed competition.

Use of sicklepod, Senna obtusifolia (L.) Irwin and Barneby, as mulch interplant in cayenne pepper, Capsicum frutescens L., production

The suitability of sicklepod as mulch interplant to smother weeds in the crop interrows and generate mulch in situ in the production of cayenne pepper was investigated on the field in 1997 and 1998 at Ibadan in the dry rainforest of Nigeria. The Senna-interplant treatment was compared with plastic-, grass- and woodchip-mulched treatments, hand weeding control and unweeded control in a randomised complete block design using four replications. Pepper fruit yield from Senna-interplant was similar to those from plastic and grass mulch in 1997, but was significantly (P<0.05) lower in 1998. Uncontrolled weed growth reduced fruit yield by 73% and 78% in 1997 and 1998, respectively, compared to the mean fruit yield from all mulched treatments. Senna-interplant, plastic, grass and woodchip mulch treatments increased the fruit yield by 21%, 36%, 45%, and 11%, respectively, compared to the hand weeding unmulched treatment. Over the two years, the weed control efficiency of the Senna-interplant, plastic, grass and woodchip mulch, and hand weeding treatments relative to unweeded control treatment were 54%, 97%, 27%, 64%, and 88%, respectively. The afternoon temperature of the soil was reduced by the straw mulch types but increased by the plastic mulch. Soil moisture loss was less under all mulch types than in hand weeding and unweeded control treatments. The predominant weeds of the experimental area were Chromolaena odorata (L.) R.M. King & Robinson, Talinum fruticosum (L.) Juss, Synedrella nodiflora Gaertn and Laportea aestuans (L.) ex Miq with relative importance values 9.8%, 8.6%, 8.3%, and 6.3%, respectively. The weed dry weight, topsoil temperature and moisture depletion negatively correlated with the performance of the pepper plants.

Evaluation of nicosulfuron for control of speargrass [Imperata cylindrica (L.) Raeuschel] in Nigeria

Nicosulfuron is a new alternative herbicide for post-emergence control of perennial weeds in maize. Field studies were conducted to evaluate the response of four maize cultivars (Low-N-Pool, TZB-SR, Oba Super-1 and Oba Super-2) and speargrass to different rates of nicosulfuron (35, 70, and 105 g a.i. ha − 1). Hand-weeded and unweeded plots were controls. All plots that received nicosulfuron had significantly lower speargrass shoot biomass than the unweeded control 3 weeks after treatment and at crop harvest. Maize biomass was highest in the weeded control in both years. In 2000, maize biomass in plots that received 35 g a.i. ha − 1 of nicosulfuron was similar to that in the unweeded control, and in both cases was higher than in all the other nicosulfuron treatments. In 2001, all rates of nicosulfuron produced significantly higher maize biomass than the unweeded control. Higher maize grain yield was obtained from 70 and 105 g a.i. ha − 1 than from 35 g a.i. ha − 1. All the cultivars responded similarly to nicosulfuron. A linear regression equation is given for grain yield and speargrass biomass. Our results suggest that nicosulfuron has the potential for effective speargrass control in Nigeria.

Control of Imperata cylindrica (L.) Raeuschel (speargrass) with nicosulfuron and its effects on the growth, grain yield and food components of maize

Imperata cylindrica (speargrass) is one of the most invasive weeds in the moist savannah zone of sub-saharan Africa. This study was conducted in 2001 and 2002 at Ijaye and Ilorin, Nigeria, to investigate the influence of four nicosulfuron doses (35, 70, 105, and 210ga.i./ha) on the performance of maize, and its efficacy in the control of Imperata. The experiment was designed as a split-plot with three replications. Nicosulfuron was applied 2 weeks after planting maize. Hoe weeded and unweeded treatments were controls. In both years, 7 weeks after treatment, the unweeded control had lower maize leaf area index (LAI) (19% at Ijaye and 25% at Ilorin) than the weeded control. Maize LAI was highest in plots that received 35ga.i./ha of nicosulfuron at Ijaye and the weeded control at Ilorin in both years. All plots that received nicosulfuron had significantly higher maize grain yield than the unweeded control at both locations in both years. Maize grain yield in the weeded control was similar to plots that received nicosulfuron at 35–210ga.i./ha at Ijaye in 2002, 70–210ga.i./ha at Ilorin in 2001, and 35ga.i./ha at Ilorin in 2002. The protein content of maize in the weeded control and at 70ga.i./ha was similar and higher than that at doses of 105 and 210g a.i./ha (P⩽0.01) while the carbohydrate content was not significantly different. The unweeded control had significantly higher weed LAI, shoot and rhizome biomass than all other treatments at both locations in both years (P<0.05). An increase in the nicosulfuron dose led to a decrease in weed LAI. Imperata rhizome biomass in the weeded control was similar to that in all nicosulfuron-treated plots. The findings of this study show that nicosulfuron is a suitable postemergence herbicide for speargrass control in maize in the moist savannah of Nigeria.

Weed suppression in a broccoli–winter rye intercropping system

Interseeded cover crops have the potential to maintain and improve soil quality, reduce the incidence of insect pests, and suppress weeds in vegetable production systems. However, the successful use of interseeded cover crops has been limited by their tendency to either inadequately suppress weeds or suppress both weeds and the crop. We hypothesized that in irrigated broccoli production, winter rye could suppress annual weeds through rapid emergence and shading, without adversely affecting the taller transplanted broccoli crop. In field experiments conducted in New York from 1999–2001, broccoli was cultivated at 0, 10, or 10 and 20 d after broccoli transplanting (DAT), with or without rye at the final cultivation. Rye interseeded at 0 DAT suppressed weeds and improved yields relative to unweeded controls but resulted in broccoli yield losses relative to weed-free controls in 2 of 3 years. Rye seeded at either 10 or 20 DAT did not reduce broccoli yields but had little effect on weeds for a given level of cultivation and resulted in Powell amaranth seed production of up to 28,000 seeds m−2. Rye interseeded at 0 DAT reduced light availability to weeds in 2000 but not in 2001 when Powell amaranth avoided shading from rye through rapid emergence and vertical growth. In greenhouse pot experiments, low temperatures for 7 d after seeding delayed the emergence of Powell amaranth by 3 d relative to rye and increased the suppression of Powell amaranth by rye from 61 to 85%. Our results suggest that winter rye may be more successfully integrated into broccoli production (1) when sown at higher densities, (2) in locations or seasons (e.g., spring) with lower initial temperatures, and (3) in combination with other weed management tools.

Post emergence spraying of clopyralid, picloram or pyridate in broccoli, Chinese cabbage, cabbage, or cauliflower kills weeds, with minimal crop damage

We investigated potential post-emergence herbicides for managing broadleaf weeds in broccoli, Chinese cabbage, cabbage, and cauliflower, as no products are currently registered for these uses in Australia. Subsequent to spraying clopyralid, picloram, or pyridate 5�weeks after direct-sowing broccoli or Chinese cabbage, or transplanting cabbage or cauliflower seedlings, we recorded crop phytotoxicity symptoms, measured marketable crop yields, and assessed weed control achieved. Neither maximum application rates of 90 g clopyralid/ha, nor 45�g clopyralid/ha mixed with 30 g picloram/ha, adversely affected vegetable yields. Spraying 60 g/ha clopyralid controlled burr medic (Medicago polymorpha), and suppressed common sowthistle (Sonchus oleraceus). Applying 90 g clopyralid/ha, or mixing 22.5 g clopyralid/ha with 15 g picloram/ha, controlled both burr medic and common sowthistle. At the rates tested, neither clopyralid nor picloram affected deadnettle (Lamium amplexicaule). Applying 450 g pyridate/ha caused chlorotic spotting of the sprayed vegetable leaves, but did not affect marketable yields of broccoli, cabbage or cauliflower. This rate controlled deadnettle, reduced sowthistle growth by only 30–50% compared with an unweeded control, and had no impact on burr medic. Spraying 900 g pyridate/ha increased the severity and persistence of chlorotic spotting, and resulted in lower broccoli and Chinese cabbage yields than obtained in the best treatments in the respective experiments. Cabbage and cauliflower yields were unaffected by spraying 900 g pyridate/ha. This rate improved sowthistle control to a commercially acceptable level. Our studies suggest that both clopyralid and pyridate could be successfully utilised in Australian vegetable brassica production, providing issues of the residual activity of clopyralid on following crops, and optimal application rates and timing for pyridate, were resolved.

Weed management in turmeric (Curcuma longa) through integrated approaches

A field study was conducted at Ludhiana during 2006-07 and 2007-08 and at Nawanshah during 2007-08 to find out effective and economical approaches for weed management in turmeric (Curcuma longa L.). Pre-emer- gence pendimethalin 1.0 kg, metribuzin 0.70 kg and atrazine 0.75 kglha, each integrated with one hoeing at 60 days, paddy straw mulch 6 t and 9 tlha; paddy straw mulch 6 t (recommended), 9 tlha alone and 6 tlha + two hoe- ing at 60 and 90 days; three hoeing at 30, 60 and 90 days and unweeded control were evaluated. Losses in rhi- zome yield due to weeds vary from 63.9 to 76.5%. Straw mulch 9 tlha significantly reduced weed dry matter and recorded 29.2% higher rhizome yield than 6 tlha. Averaged over two locations, pendimethalin + straw mulch 9 tlha revealed the highest weed control efficiency (84.2%), fresh rhizome yield (29.6 tlha), herbicide efficiency index (1 1.2), net returns (103 0 l o 3 Rslha) and benefit : cost ratio (2.30) and was at par with metribuzin and atrazine, both integrated with straw mulch 9 tlha. The fresh rhizome yield with straw mulch 9 tlha + herbicide combination was 48.2, 14.9, 15.3 and 225.5% higher than straw mulch 6 t, 9 tlha alone, 6 tlha + herbicide and unweeded con- trol, respectively. Different weed control measures led to 104.8ii289.1, 72.7ii220.4 and 90.5A278.1% increase.in N, P and K uptake by crop, respectively, over unweeded control. Uncontrolled weeds removed 60.6, 59.9 and 73.6% of total nutrients utilized by both crop and weeds. Integrated use of paddy straw mulch 9 tlha with either of pendimethalin 1.0 kg, metribuzin 0.70 kg and atrazine 0.75 kglha was adjudged very effective for weed control and attaining the highest productivity and profitability in turmeric.

Weed-population dynamics and fennel (Foeniculurn vulgare) growth as influenced by integrated weed management

A field trial was conducted during winter (rabi) season of 1991 -92 to 1993-94 at S.K.N. College of Agriculture, Jobner under semi-arid condition of Rajasthan. All the weed-control treatments except metolachlor @ 0.5 and 1.0 kglha significantly reduced the population of Chenopodium murale L. compared with unweeded control. Heliotropium ellipticum Ledebour was tolerant to oxyfluorfen @ 0.15 kglha, pre-emergence application of oxyfluorfen @ 0.15 kglha, pendimethalin @ 1.0 and 1.5 kg/ha, pre-plant incorporation of fluchloralin Q 1.0 and 1.5 kglha, pre-plant incorporation of fluchloralin @ 0.75 and 1.25 kglha, . hand-weeding once (25 DAS) and twice (25 and 50 DAS, weed-free treatment and lower doses of herbicides supplemented with hand-weeding once (50 DAS) significantly reduced the total mean density (except at harvest with fluchloralin @ 0.15 kgtha) and loss in seed yield (except oxyfluorfen Q 0.15 kg/ ha and fluchloralin @ 0.75 kgtha). All the weed control measures significantly increased the plant height and crop biomass (except metolachlor @ 0.5 and 1.0 kglha) over unweeded control. Lower doses of herbicides except metolachlor supplemented with hand-weeding once, pendimethalin @ 1.5 kglha, hand- weeding once and twice and weed-free treatment significantly increased the harvest index compared with unweeded control. Maximum benefit : cost ratio of 3.35 was obtained under weed-free condition, followed by pendimethalin @ 1.0 kglha supplemented with hand-weeding once (2.75). Among the herbicidal treatments, metolachlor @ 0.5 and 1.0 kglha was least effective in reducing the weed density and loss ii seed yield.

Effect of methods of sowing and weed management on yield of chicory (Cichorium intybus)

A field experiment was conducted during Though the weed-management treat- winter season of 1992-93 to study the effect ments barring unweeded control did not dif- of methods of sowing and weed fer significantly among themselves: how- management on weed control and root yield ever, proved superior to the unweeded con- of chicory (Cichorium intybus L.) at Anand. trol for weed density (at 60 days). The dry The soil was loamy sand. Nine treatments weight of weeds was influenced significantly comprised 2 herbicides (trifluralin @ 0.5 by different treatments. Methods of sowing kglha and pendimethalin @ 0.5 kglha both treatments and 2 hand-weeding treatments as pre-emergence), 2 conventional weeding proved effective in reducing dry weight of treatments (hand-weeding at 30 days after weeds. Though the herbicides and 1 hand- sowing and 2 hand-weedings at 30 and 60 weeding treatments significantly reduced days), 2 methods of sowing (line sowing by the dry weight of weeds compared with the seed drill and shallow sowing through unweeded control, these did not show supe- furrow opened by kudali each at 20 and 30 riority to methods of sowing treatment and 2 cm width) along with unweeded control, hand-weedings (broadcast sown). Both the were tried in randomized block design with herbicides found more or less equally effec- 3 replications. Chicory cv. Rexor was tive in controlling Chenopodium album L., sown on 20 November 1992 and harvested Digitaria sanguinalis (L.) Scop. and on 17 April 1993. The crop was uniformly Eragrostis cilianenisis (All.) Link compared fertilized with 100 kg N + 50 kg P,O, + 50 the unweeded treatment. Both herbicides kg &amp;O/ha as basal application in the form significantly reduced the weed density com- of urea, single superphosphate and muriate pared with the unweeded control. Pate1 and of potash respectively. The crop was Upadhyay (1989) noted the effectiveness of irrigated 5 times during the crop season. pendimethalin in reducing the weed density Species-wise weed density was recorded throughout the growth period of chicory. using 0.25 m2 quadrate from randomly Significant differences were observed in selected 2 spots in a plot at 60 days. fresh as well as dry weight of chicory roots However, predominant weeds counted due to different treatments. Significantly separately. In hand-weeding, the count was highest yields of chicory (20,648 kg fresh taken just before the operation and and 4,750 kg dry rootslha) were recorded subsequently the dry weight was recorded. with 2 hand-weedings when compared wxth

Effect of fertility levels and herbicides on growth, yield and nutrient uptake of direct-seeded rice (Oryza sativa)

A field experiment was conducted during the rainy seasons of 1999 and 2000, to find out the effect of fertility levels and herbicides on growth, yield and nutrient uptake of direct-seeded rice (Oryza sativa L.). The fertility level up to N4,P4,K,, + 25 kg ZnSO, + foliar spray of micronutrient mixture (thrice) proved the best, producing 6.34 qlha extra grain and Rs 6,9681ha extra net return over no fertility level. Hand-weeding (20 and 40 days after sow- ing) showed 72% weed-control efficiency with additional grain yield up to 9.91 qlha and net return up to Rs 5,0421ha over unweeded control. Pendimethalin 1.0 kglha or anilophos 0.40 kglha each with 2,4-D (Na-salt) 0.60 kglha showed 50 to 51% weed-control efficiency and proved the best substitute of hand-weeding (twice), the ex- tra net return being Rs 3,689 and Rs 3,074/ha, respectively, over unweeded control. The seed protein and nutri- .ent uptake were also increased significantly with increasing fertility levels and the herbicides over their respec- tive controls.

Effect of land configuration and weed management in onion (Allium cepa)

A field experiment was conducted to examine the effect of different planting patterns and weed management practices on weed growth and productivity of onion ( Allium cepa L.) during rabi 2006-07 and 2007-08. The experi- ment was laid out in split-plot design with planting patterns of onion in main-plots (flat and raised bed planting with or without rice straw incorporation) and weed management practices viz., pendimethalin @ 0.75 kg/ha, oxyflourfen @ 0.225 kg/ha, fluchloralin @ 1.125 kg/ha, two hand weedings and control (unweeded) in sub-plots. Weed popu- lation and dry matter accumulation of weeds under different planting patterns and straw management techniques remained unaffected throughout the crop growth period and at uprooting. Yield attributes and bulb yield were not significantly influenced by planting patterns. Population and dry matter accumulation of weeds were significantly reduced with the application of oxyflourfen, pendimethalin and two hand weedings, when compared with fluchloralin and unweeded control during both years of investigation. Application of oxyflourfen gave the highest bulb yield, which was at par with pendimethalin and two hand weedings. These treatments gave significantly more bulb yield than fluchloralin and unweeded control. The highest net returns obtained with flat bed sowing with rice straw incorporation. Among the different weed control treatments, the maximum net returns of 185.6103/ha with BCR 7.63 registered with oxyflourfen. Unweeded control treatment recorded the lowest net returns of 94.3103/ ha with BCR 4.10.

Growth and yield of coriander (Coriandrum sativum) as influenced by weed management and nitrogen levels

A field study was carried out during winter ( rabi) season of 200708 and 200809 at Jobner, Rajasthan to evaluate the effect of weed-management treatments and nitrogen levels on weed-control efficiency and growth, yield and economics of coriander ( Coriandrum sativum L.). Two hand-weedings done 20 and 40 days after sowing and pendimethalin at 1.0 kg/ha + hand-weeding at 40 days after sowing were the most effective in reducing the density and dry weight of weeds and improving the weed-control efficiency. Oxadiargyl at 0.06 kg/ha + hand-weed- ing at 40 days after sowing represented the lowest weed density and controlled the weeds to the extent of 94.9%. Two hand-weedings done at 20 and 40 days after sowing recorded the highest plant height, umbels/plant and test weight. It also provided the maximum seed and straw yields (1.37 and 2.58 t/ha) of coriander that were 164.7 and 116.9% more than unweeded control respectively. Pendimethalin at 1.0 kg/ha + hand-weeding at 40 days after sowing was also found equally effective in increasing the growth and yield attributes as well as yield. The highest number of branches/plant, dry matter, umbellets and seeds/umbel were obtained under this treatment. It provided the seed and straw yields of 1.36 and 2.56 t/ha, respectively, indicating an increase of 162.5 and 116.9% than unweeded control. It also recorded the highest harvest index (35.01%) and lowest weed competition index (0.73%) among all the treatments. Providing seed yields of 1.20 and 1.17 t/ha with weed competition indices of 12.3 and 14.4%, 1 hand-weeding at 20 days after sowing and pendimethalin at 1.0 kg/ha were the next better and statisti- cally similar treatments. The highest net returns ( 55,841/ha) and benefit: cost ratio (2.39) were obtained with 2 hand-weedings at 20 and 40 days after sowing treatment. Pendimethalin at 1.0 kg/ha + hand-weeding at 40 days after sowing was found at par with hand-weeding twice fetching net returns of 54,308 and benefit: cost ratio of 2.3. Application of 75 kg N/ha significantly increased the growth and yield of coriander over preceding levels. It en- hanced the seed yield of coriander to the extent of 11.9, 32.7 and 84.3% over 50 and 25 kg N/ha and control re- spectively. This level of N also maximized the net returns ( 54,412/ha) and benefit: cost ratio (2.35).

Conservation tillage and weed management for improving productivity, nutrient uptake and profitability of soybean (Glycine max) grown after wheat (Triticum aestivum)

A field experiment was conducted during 2010 and 2011 at New Delhi to study the performance of soybean [ Glycine max (L.) Merrill] grown after wheat [ Triticum aestivum (L.) emend Fiori &amp; Paol] under four tillage and crop establishment practices, viz. conventional tillage (CT)flat-bed, CTraised-bed, zero tillage (ZT)flat-bed and ZT raised-bed along with four weed management options, viz. unweeded control, pendimethalin @ 0.75 kg/ha as pre- emergence (PE) + hand weeding (HW), pendimethalin @ 0.75 kg/ha as PE + imazethapyr @ 75 g/ha as post- emergence (POE), and wheat straw mulch @ 5 t/ha + imazethapyr @ 75 g/ha as POE. Total weed density and dry matter was comparatively higher under ZT than CT, but adoption of chemical + cultural weed control methods led to 79.5-82.5% weed control efficiency. Seed yield of soybean was equal under CTraised-bed, CTflat-bed and ZTraised-bed, which was 11.7% more than ZT flat-bed. Similarly, pendimethalin + HW, pendimethalin + imazethapyr, and wheat straw mulch + imazethapyr resulted in almost similar weed control, and thus gave compa- rable seed yield, which was 39.142.7% higher than unweeded control. Weed and crop biomass followed oppo- site trends, and the seed yield decreased by 0.2 t/ha for an increase of 100 g/m2 in weed dry weight. Concentra- tion of N, P and K in seed and stover of soybean was not influenced but the uptake was highest under CTraised- bed, which was on par with ZTraised-bed. Nutrient uptake was highest under pendimethalin + HW, which was significantly higher than under pendimethalin + imazethapyr, and wheat straw mulch + imazethapyr. The highest net benefit:cost was under ZTraised-bed and pendimethalin + imazethapyr or pendimethalin + HW, followed by CTraised-bed under the same weed control treatments. It was concluded that soybean can be grown under per- manent raised-bed with pre- and post-emergence herbicides for realizing higher productivity and profitability.

Production potential and nitrogen use efficiency of inter specific and intra hirsutum cotton hybrids under graded levels of nitrogen and weed control methods

. . A field study was conducted during the winter seascn of 1997 and 1998 at Tamil Nadu Agricultural University, Coimbatore. Two hybrids (inter specific TCHB 213 and intra hirsutum Surya ) were evaluated for their production potential under 3 N levels (90. 120, and 150 kglha) and 4 weed control methods (Pendimethalin 1.0 kg 1 hand weeding, glyphosate 1.0 kg 1 hand weeding, hand weeding twice and unweeded control). The hybrids were grown following the recommended spacing of 90 cm x 60 cm for Surya and 120 cm x 60 cm for TCHB 213 . Among the hybrids, TCHB 213 gave better yield attributes and yield , on per plant basis. But Surya gave significantly more yreld than TCHB 21 3 on t unit area basis. The response to applied N was increasing at increasing rate up to the highest level (150 kglha) of N. But the N use efficiency decreased with increase in N level. Among the weed control treatments, hand weeding twice recorded significantly higher seed cotton yield and N use efficiency which was closely followed by glyphosate hand weeding.

Effect of early post-emergence herbicide for control of weeds in winter irrigated upland cotton (Gossypium hirsuttlm)

A study was carried out to evaluate the effect of trifloxysulfuron with and without adjuvant against weeds in upland cotton (Gossypium hirsutum L.) during the winter seasons of 2003-04 and 2004-05 at the Tamil Nadu Agricultural University, Coimbatore. Weeds,viz. Tranthema portulacastrum L., Chloris inflata Link; syn. C. barbata Sw. and Cyperus rotundus L., were the dominant weeds of the experimental fieid. Trifloxysulfuron effectively con- trolled T: portulacastrum and C. rotundus. Trifloxysulfuron Q 10 and 20 glha with and without adjuvant provided 85 to 91% weed-control efficiency compared to unweeded control. Among the treatments, the maximum cotton yield of 16.89 and 17.96 qlha was observed in trifloxysulfuron 10 glha + adjuvant during the winter season of 2003-04 and 2004-05 respectively. Minimum seed-cotton yield of 8.97 and 8.76 qlha was obtained in unweeded control in first and second year.

Chemical control of weeds in saftlower (Carthamus tinctorius)

S&amp;ov/er (Carthamus tinctorius L.) is an terslha), pendimethalin (0.75 and 1.25 li- important oilseed crop. It is poor weed com- terslha), terbutryn (0.50 and 0 75 kglha), petitor at initial stages of growth. A field methabenzthiauron (1.OO and 1.50 kgtha), trial was conducted during winter (rabi) isoproturon (0.75 and 1.00 kglha), 2 hand- season of 1988-89 at Ludhiana, to find out weedings and a unweeded control. The ex- suitable herbicide. The soil was loamy sand, periment was replicated 4 times in having pH 8.0, low in organic carbon randomized block design. (0.17%), available nitrogen (I 12.2 kglha), After the lay out of the experiment, phosphorus (1 1.6 kglha) and medium in fluchloralin was applied before the sowing --- available potassium. The treatment con- (pre-plant) and all other herbicides were ap- - , - sisted of 2 levels of each alachlor (1.5 and plied after the sowing of the experiment as 2.5 litrestha), fluchloralin (0.75 and 1.25 li- pie-emergence. ~

Weed control in rice (Oryza sativa) nursery

An experiment was conducted during rainy (kharif) season 1991-93 to study weed control in rice (Oryza sativa L.) nursery in medium black soil, with 6 treatments consisting 3 herbicides (butachlor 1.5 kg, thiobencarb 1.5 kg and anilophos 0.3 kg a.i.lha) and other treatments being hand-weeding at 20 days after sowing, Gliricidia leaves 1 kglmZ as mulch and unweeded control. The fresh weight of rice seedlings due to application of herbicides and hand-weeding once were found significantly superiorto the unweeded control. The significant reduction in weed biomass was due to application of herbicides and hand-weeding once in comparison with the treat- ments of unweeded control and Gliricidia leaves. The saving due to use of weedicides and Gliricidia leaves for 0.10 ha nursery area over manual weeding was Rs 225 and 153 respectively.

Effect of weed-control measure on growth and yield of summer greengram (Phaseolus radiatus)

A field experiment was carried out during 1995-96 and 1996-97 to study the effect of different weed-control measures on summer greengram (Phaseolus radiatus L.). Pre-plant application of Fluchloralin 0.75 kg/ha resulted in maximum seed yield of 1,192.48 and 1,305.51 kg/ha compared with 755.1 5 and 81 1.23 kg/ ha under unweeded control during 1995-96 and 1996-97 respectively. This treatment also resulted in the maximum weed-control efficiency (92.432%). Pre- emergence application of Pendemethalin @ 0.75 kglha showed depressing effect on crop growth. However, at lower dose, i.e. 0.50 kglha, followed by 1 hoeing showed 90.75% weed-control efficiency with little effect on growth and - - yield of summer greengram.

Performance of metsulfuron methyl and pendimethalin alone and their mixtures with isoproturon on weed control in wheat (Triticum aestivum) seed crop

A field experimental was conducted during the winters of 1996 97 and 1997 98 to study the comparative performance of different herbicides, their combinations and their reduced doses for weed control in wheat (Triticum aestivum L. emend. Fiori Paol.) seed crop. Unchecked weeds caused nearly 37.7% seed yield loss. Maximum seed yield of 39.9 and 33.66 qlha was recorded in weed free treatment, respectively, during both the years. This high yielding treatment was significantly at par with weed free season long and sequential application of herbicides and herbicide mixture, but was statistically significant to full and half doses of pendimethalin and metsulfuron methyl in both the years. Pendimethalin Q 1.0 kg a.i./ha and metsulfuron C.008 kg a.i./ha significantly increased seed yield over unweeded control. Reduced dose of isoproturon 8 0.05 kg a.i./ha, pendimethalin 0.5 kg a.i./ha and metsulfuron Q 0.004 kg a.i.1 ha was least effective in controlling weeds and had minimum impact on enhancing seed yield over the control.