Weed Science

The experiment was conducted at the Research Farm, Department of Agronomy, PAU, Ludhiana, during the Rabi seasons of 2006-07 and 2007-08 to study the effect of different planting patterns and straw management techniques on residues of different herbicides in soil at different intervals and grain and straw at harvest and on growth and development of few test crops through bioassay studies. The experiment was laid out in strip plot design with planting patterns of wheat in main plots and weed control treatments in sub-plots. Herbicidal treatments were applied as post-emergence at their respective doses. Residues of sulfosulfuron, mesosulfuron+iodosulfuron and pinoxaden were detected at 1 day after spray in soil depth 0-15 cm only but residues of herbicides were not detected in soil at other observational periods i. e. 30 and 60 DAS and at harvest as well as in grain and straw at harvest by analytic method. Nine kharif season crops viz., maize, bajra, sorghum, cotton, summer moong, bhindi, dhaincha, bottle gourd and muskmelon were sown after harvesting of wheat in four replications for bioassay studies. Bioassay studies indicated no residual toxicity of pinoxaden on any test crop. However, application of sulfosulfuron and mesosulfuron+iodosulfuron showed residual toxicity on maize, bajra, sorghum and bottle gourd, whereas no residual toxicity of these two herbicides was observed in cotton, summer moong, bhindi, dhaincha and muskmelon.

A field experiment was conducted at Jabalpur during winter seasons of 2001-02, 2002-03, 2003- 04 and 2004-05 to study the influence of tillage and herbicides on weed dynamics, yield and soil properties under rice-wheat system in vertisols. Irrespective of the tillage, population of Phalaris minor and Chenopodium album decreased and that of Avena ludoviciana and Medicago hispida increased over time. Zero tillage reduced the population of P. minor and C. album but increased the population of A. ludoviciana as compared to conventional tillage. Application of clodinafop at 0.06 kg/ha fb 2, 4-D ethyl ester at 0.50 kg/ha effectively controlled both grassy and broad-leaved weeds and produced 77.8% higher grain yield than that of isoproturon 1.0 kg + 2,4-D 0.50 kg/ha. Under moisture stress, zero tillage retained more soil moisture than conventional tillage. Tillage and weed control did not affect the physicochemical properties of soil.

Isoproturon, clodinafop and sulfosulfuron alone at 750, 60 and 30 g/ha, respectively, and tank mixture of isoproturon at 500 g/ha + 2, 4-D at 500 g/ha, isoproturon at 500 g/ha + clodinafop at 30 g/ha and isoproturon at 500 g/ha + sulfosulfuron at 15 g/ha were evaluated against mixed weed flora in wheat. All the herbicide treatments significantly reduced the dry weight of complex weeds, although they differed in their effect on weed species. While sulfosulfuron and clodinafop alone and as a tank mixture with isoproturon effectively controlled grassy weeds than all other herbicide treatments, the tank mix application of isoproturon at 500 g/ha + 2, 4-D at 500 g/ha and isoproturon at 500 g/ha + sulfosulfuron at 15 g/ha were equally effective against broadleaf weeds. The broadleaf weeds being dominant in the experimental field, the overall weed density and dry matter production at different stages of crop growth were minimized by isoproturon at 500 g/ha+sulfosulfuron at 15 g/ha and isoproturon at 500 g/ha+2, 4-D at 500 g/ha. Uninterrupted weed growth depleted 20.97 kg N, 3.13 kg P and 26.94 kg K/ha, while it was lowest with isoproturon at 500 g/ha + sulfosulfuron at 15 g/ha. Maximum uptake of N (150.20 kg/ha), P (41.00 kg/ha) and K (194.14 kg/ha) by wheat crop was in plots treated with tank mixture of isoproturon at 500 g/ha + sulfosulfuron at 15 g/ha, while in weedy check plots N, P and K uptake by crop was 87.87, 23.82 and 118.04 kg/ha, respectively. Uncontrolled weeds in weedy check plots reduced wheat yield by 31.4% as compared to herbicide treated plots. Highest grain yield obtained with isoproturon at 500 g/ha + sulfosulfuron at 15 g/ha (58 q/ha) followed by isoproturon at 500 g/ha + 2, 4-D at 500 g/ha (55.34 q/ha) was significantly higher than all other treatments. Among nutrient management treatments, application of 75% RDF+vermicompost at 1.5 t/ha and 50% RDF + vermicompost at 3.0 t/ha resulted in significant increase in weed dry matter, NPK uptake, chlorophyll and protein content and grain and straw yield over RDF alone

To evaluate the effect of irrigation levels and chlorsulfuron doses on productivity and water use of wheat, a field experiment was conducted at Research Farm of CCS Haryana Agricultural University, Hisar, India during rabi seasons of 1998-99 and 1999-2000. Five irrigations (21, 45, 65, 85 and 105 DAS) applied in wheat resulted in highest grain yield and consumptive water use compared to two (21 and 85 DAS) and three (21, 65 and 105 DAS) irrigations. However, the water use efficiency (WUE) was maximum with two irrigations. Increase in the WUE of wheat due to two irrigations over three and five irrigations was 13.7 and 31.8% during 1998-99 and 9.5 and 27.0% during 1999-2000, respectively. More frequent irrigations (five) resulted in more soil moisture extraction from upper and medium soil layers, while two irrigations extracted more water from deeper layers. Different herbicidal treatments had no marked effect on water use by wheat. Maximum grain yield of wheat (4553 and 4849 kg/ha) was attained in the plots treated with chlorsulfuron at 30 g/ha which was statistically at par with its lower dose (20 g/ha)

A field experiment was conducted at Varanasi during 2005-06 and 2006-07 to find out the most sustainable and economically feasible weed management technologies for realizing high yield of direct seeded rice (Oryza sativa L.)-zero till wheat (Triticum aestivum L. emend. Fiori & Paol.) system. The treatments comprised five different weed management practices for rice (anilophos 500 g/ha, wheat straw mulch 2 t/ha, eucalyptus leaf leachate spray 3% at 30 days after sowing (DAS), stale seed bed and weedy check) and wheat (mechanical weeding at 15 and 30 DAS, rice straw mulch 2 t/ha, neem oil spray 3% at 30 DAS, sulfosulfuron 25 g/ha at 30 DAS and weedy check) under same rates of seed (75, 100, 125 and 150 kg seeds/ha). In rice crop, the seed rate of 100 kg/ha caused the highest decrease in weed dry matter accumulation and led significantly higher rice yield and NPK uptake over other seed rates. Application of anilophos at 500 g/ha recorded significantly lower dry matter accumulation of weeds, and in turn increased rice yield and NPK uptake than the other weed management practices. This treatment gave 45.4% increase in rice grain yield over weedy check. In case of wheat grown after rice, 125 kg seed/ha reduced dry matter accumulation of weeds, and resulted in the highest wheat yield and NPK uptake which was similar to 100 kg seed/ha, but was significantly superior to 75 and 150 kg seeds/ha. Mechanical weeding done twice at 15 and 30 days stage was found most effective in reducing weed dry matter accumulation, and maximizing wheat yield and NPK uptake which was at par with sulfosulfuron 25 g/ha at 30 DAS. Mechanical weeding at 15 and 30 DAS registered 31.4% increase in wheat grain yield over weedy check. Net return and benefit: cost ratio in rice-wheat system were the highest (Rs. 41347/ha and 2.66) with 100 kg seed/ha to both the crops and in weed management treatments, maximum net return and benefit: cost ratio Rs.13310/ha and 0.87 were recorded with anilophos 500 g/ha in rice, and Rs.29922/ha and 1.82 with sulfosulfuron 25 g/ha in wheat. For realizing higher yield, economic gain and effective weed management in direct seeded rice and zero-till wheat system, 100 kg seed/ha of rice and wheat should be applied with anilophos at 500 g/ha to rice crop and 125 kg seed/ha alongwith sulfosulfuron 25 g/ha at 30 DAS to the succeeding wheat crop.

Field experiments were conducted at Research Farm of the Department of Agronomy, PAU, Ludhiana during 2006, 2007 and 2008 on loamy sand soil. The performance of different genotypes of rice under direct seeded conditions were variable. During 2006, performance of PR-115 and PR-113 was found to be significantly superior to other tested genotypes because of more smothering effect on weeds by these cultivars. Among IRRI biotypes, the performance of IR-72164-13-7-2 and IR-71703-587-1-3 was found satisfactory. During 2007, PAU-201, PR-115 and PR-116 recorded higher grain yield both under weedy and weed free conditions but among IRRI varieties 17 A/R 10 produced highest seed yield. During 2008, PAU-201 and PR-115 performed better than other varieties and among rice hybrids RH-257 outyielded other tested hybrids and it was followed by Arize-6444 and Arize-6129. These hybrids smoothered weeds as indicated by less dry matter accumulation by the weeds.

Screen house studies were carried out under controlled conditions during the rainy seasons of 2006 and 2007 at CCS Haryana Agricultural University, Hisar to evaluate the influence of seeding depth and flooding duration on the emergence of Ammania baccifera, Cyperus alutatus, C. arenarius, C. difformis, C. iria and Scirpus roylei. Seeding depths of 0, 0.5, 1, 2 and 4 cm and flooding durations of 0, 4, 8, 16, 32 and 64 days were maintained with four replicated pots. Maximum emergence was recorded from 0.5 cm and surface (0 cm) which decreased by 44 and 80% at 1 and 2 cm depths compared to 0.5 cm depth and no emergence was recorded from 4 cm or higher depths, data averaged over species. Emergence of S. roylei was 80% at 0.5 cm and decreased by 9 and 46% at 1 and 2 cm depths, whereas 63% lower emergence was recorded from 0 cm depth, respectively. Emergence of A. baccifera, C. difformis and C. iria was similar from 0 and 0.5 cm but decreased significantly with increasing depths, whereas C. arenarius and C. alutatus recorded 20 and 10% lower emergence, respectively, from 0.5 cm compared to surface placed seeds and no emergence was recorded from 2 cm depth. However, 43, 27 and 15% emergence was recorded for S. roylei, A. baccifera and C. iria from 2 cm depth, respectively. Flooding caused significant reduction in the emergence of C. arenarius and C. alutatus, but had no adverse effect on S. roylei. Flooding encouraged emergence of C. difformis and C. iria as higher emergence was observed with increasing flooding period from 0 to 16 days (d), whereas 16 d flooding caused 100% reduction in the emergence of C. arenarius. Conversely, S. roylei emergence inhibited without flooding and flooding duration of 16 d or more resulted in >90% emergence. Increased flooding duration was positively correlated with the emergence and growth of all species except C. arenarius and C. alutatus. A flooding duration of 64 d reduced emergence of C. difformis and C. iria, but still it was similar to no flooding and their growth was more compared to lower flooding durations. Similarly, A. baccifera emergence was 18% lower with 64 d flooding compared to no flooding, but had no adverse effect on plant growth and no inhibition in emergence was observed in S. roylei with 64 d flooding. The results indicate susceptibility of C. arenarius and to a lower extent of C. alutatus to flooding, but emergence and growth of other Cyperus spp., S. roylei and A. baccifera was stimulated by water. The test species behaved differently to moisture levels and seeding depths and this information can be used under different conditions using tillage operations and water management for lowering their menace.

Pot studies were carried out at CCS Haryana Agricultural University, Hisar during 2006-07 and 2007-08 to evaluate the effect of water temperature for spraying clodinafop-propargyl formulations on several biotypes of P. minor and response to alternate herbicides. Clodinafop formulations (Topik, Point, Rakshak Plus, Moolah and Jai-Vijay) at 60 g/ha were sprayed using water at temperatures of 8, 25 and 40OC on P. minor biotypes J-35, KUL, F-42, B-6, H-2, Bajekan during 2006-07 and Garhi Birbal, Jyotisar, Sarwan, Nangla, Jat and Lalodha during 2007-08. Isoproturon 1.5 kg/ha, chlorotoluron 1.0 kg/ha, premix of sulfosulfuron+metsulfuron (Total) 32 g/ha, mesosulfuron+iodosulfuron (Atlantis) 14.4 g/ha, pinoxaden 45 g/ha, fenoxaprop-P-ethyl 100 g/ha and quizalofop-P-ethyl 100 g/ha were sprayed using normal water temperature (25OC) on P. minor biotypes. Chlorotoluron was replaced with clodinafop 90 g during the second year. Mortality of P. minor biotypes was significantly decreased with clodinafop formulations when water temperature of 8OC was used for spraying compared to 25 or 40OC temperature water. There was no difference in mortality of P. minor biotypes between 25 and 40 OC temperature water for spraying, eight weeks after treatment (WAT); however, significant differences in dry matter accumulation by P. minor biotypes were recorded due to water temperature for spraying clodinafop. Clodinafop formulation, Topik was more effective compared to Jai-Vijay, but differences were non-significant among different formulations. Significant variations in mortality and dry weight were observed among P. minor biotypes with different herbicides. Chlorotoluron provided effective control of isoproturon resistant biotypes, which were also susceptible to quizalofop. Lalodha biotype was highly resistant to fenoxaprop, isoproturon and clodinafop and even increased rate of 90 g/ha clodinafop also failed to effectively control this biotype. Pinoxaden, sulfosulfuron+metsulfuron, mesosulfuron+iodosulfuron and quizalofop; however, provided 90-100% control of these resistant biotypes. Variations in mortality by pinoxaden, sulfosulfuron+metsulfuron and mesosulfuron+iodosulfuron herbicides were also observed in some biotypes which need further confirmation.

Fenoxaprop-P-ethyl resistant populations of Phalaris minor Retz. have been observed in wheat fields in India. A quick and accurate means of confirming resistance is necessary to take timely management decisions. Seedling growth and chlorophyll development as affected by the doses of herbicides in Petri dishes were estimated in this study. ED50 values obtained for chlorophyll development compared to the seedling growth, discriminated the two feoxaprop resistant populations from each other and from the susceptible population better and provided a close relationship with the whole plant assay. The efficacy of pinoxaden against these populations was also studied based on this parameter. The parameter has the potential to be utilized for early detection of fenoxaprop resistance in P. minor populations, and to screen these on a large scale

Raised bed planting of lentil produced significantly higher yield as compared to zero till sowing; however, it was at par with the yield obtained in flat sowing. Weed dry weight was found higher in flat bed sowing and it was the lowest in zero till sowing. Irrigating lentil at flowering stage increased the grain yield significantly over no irrigation to the tune of 9.01 and 10.73% during 2005-06 and 2006-07, respectively. This may be due to more number of pods/plant, grains/plant and 1000-grain weight recorded under irrigated treatment. Application of pendimethalin (pre-emergence) @ 1.0 kg/ha controlled weeds more effectively as compared with one hand weeding at 30 days after sowing (DAS). One hand weeding at 30 DAS and pendimethalin @ 1.0 kg/ha produced 14.09 and 30.67 during 2005-06 and 2006-07 and 30.67 and 38.10% higher grain yield over weedy check. The dominant weed flora consisted of Chenopodium album and Melilotus indica.

An on-farm trial was conducted during rabi seasons of the years 2006-07 and 2007-08 at farmers’ fields in Bangalore Rural District of Karnataka to study the effect of different mulches for controlling weeds in edible pea (Pisum sativum L.). The treatments comprised five mulches viz., white polythene, black polythene, wheat straw, newspaper and saw dust as well as hand weeding and a weedy check. Variety ‘Pusa Harbhajan’ was planted on a plot size of 5 x 1.6 m2 using randomized complete block (RCB) design, having three replications. All the parameters except plant height were significantly affected by different treatments. Maximum number of pods/plant (50.87, 48.40 and 35.87), number of seeds/pod (5.83, 5.80 and 5.50) and pod yield (2707, 2613 and 2512 kg/ha) were recorded in hand weeding, newspaper and black polythene treatments, respectively, whereas minimum values in these parameters were recorded in weedy check. All mulches were effective and gave better results than weedy check, but due to their better performance newspaper and black polythene mulching were recommended for the environment friendly and sustainable control of weeds and realizing better yields of edible pea

A study was conducted during summer season of 2001 to 2004 with an objective to document the important weeds of potato crop in Nilgiris based on their importance value index. The data were collected on species-wise weed count, fresh weight, frequency of occurrence and canopy coverage on 45th day of potato planting. The results indicated that Coronopus didymus and Polygonum nepalense were the two major weeds of potato crop in Nilgiris hills. Weed management strategy for these weeds has been suggested

An on-farm trial was conducted at farmers’ fields in the Hassan district of Karnataka during Rabi seasons of 2006-07 and 2007-08 to find out the effective and economical integrated weed control method in potato. Amaranthus viridis, Chenopodium album, C. murale and Poa annua were the major weed species in potato field. Mulch (water hyacinth) along with application of oxadiazon (0.75 kg/ha) at seven days after planting (DAP) was found most effective in controlling weed population (94 to 95%) upto 30 days of planting than that employed by only mulch (45 to 53%). The weeds were found to reduce tuber yield to the extent of 43%. Among the weed control treatments, minimum nutrient uptake by weeds and highest tuber yield were recorded with mulching+oxadiazon (0.75 kg/ha) spray at 7 DAP+one hand weeding at 25 DAP, and these were at par with weed free check. The highest net returns of Rs. 74563 and 122859/ha and maximum benefit : cost ratio of 2.75 and 3.27 were noted in mulching with water hyacinth+herbicide application at 7 DAP+one hand weeding at 25 DAP in 2006-07 and 2007-08, respectively.

Parthenium (Parthenium hysterophorus L.) is a new encroacher weed into many crops including sorghum. An attempt was made to analyse the growth of parthenium and other weeds in sorghum. In sorghum, Trianthema portulacastrum, Acrachne racemosa, Dactyloctenium aegyptium, Digera arvensis and Tribulus terrestris exhibited much higher population and dry weight than parthenium. Parthenium had inferior growth in terms of population and dry weight at 30, 60 and 90 DAS compared to most other weeds. But its weed growth rate (WGR) and weed relative growth rate (WRGR) were on the increase consistently till 90 DAS. The reverse was true for other weeds, whose growth rates (WGR and WRGR) decreased gradually over time.

An experiment was conducted at PAU, Ludhiana, during the rabi seasons of 2006-07 and 2007- 08 to study the effect of different planting patterns and straw management techniques on residues of different herbicides in onion bulbs and soil. The experiment was laid out in split plot design with planting patterns of onion (flat and bed planting with and without rice straw incorporation) in main plots and weed control treatments in sub-plots. Oxyflourfen and pendimethalin were applied one week after sowing (after first irrigation) and fluchloralin was applied as pre-plant at their respective doses as per given herbicidal treatments. Soil samples were collected from the experimental plots at 1, 30 and 60 days after spray and at uprooting from each plot from 0-15 and 15-30 cm depth and samples of onion bulbs were taken at 30, 60, and 90 days after spray and at uprooting. Soil samples of oxyflourfen 0.225 kg/ha, pendimethalin 0.75 kg/ha and fluchloralin 1.125 kg/ha treated plots taken 1 day after spray showed residues of respective herbicides. Samples of onion bulbs at 30, 60 and 90 days after spray and at uprooting stage showed no residues of applied herbicides in onion bulbs.

Greenhouse and laboratory experiments were conducted to determine the allelopathic effects of sunflower on Sinapis arvensis and Setaria viridis with a view to explore its weed seed inhibition potential. Germination of both the weeds was reduced with increasing concentration of sunflower extract and a dose-response relationship was observed. These curves provided information on LC50 and inhibition threshold concentrations of sunflower extracts. Sunflower also inhibited the growth of both the weeds in terms of root and shoot length and seedling dry weight. Inhibition of root growth was greater than that of shoot growth. Similar observations were made when the test weeds were grown in soil amended with different concentrations of sunflower extract. Reduction of chlorophyll content and water loss in the growing seedlings was also observed. The study, therefore, revealed that sunflower exerted an inhibitory effect on the growth and development of both the weeds and can be further explored in future for weed management strategies.

Temperature is one of the main factors of crop production and it influences herbicide persistence by affecting different herbicide degradation reactions in the soil. To study the persistence of trifluralin and imazethapyr affected by different temperature regimes, an experiment was carried out under lab and screen house conditions at CCSHAU, Hisar. Bioassay technique was used to quantify the persistence by employing sensitive plants of oat and mustard for trifluralin and imazethapyr bioassay, respectively. Soil treated with these herbicides at different rates (trifluralin 0.0, 0.125, 0.25, 0.5, 1.0 and 2.0 kg/ha and imazethapyr 0, 10, 20, 40, 80 and 160 g/ha) after incubation at 15, 25, 35 and 45OC temperature regimes in incubator. Persistence of herbicides affected by different temperature regimes at different herbicide rates was measured by comparing shoot and root growth, fresh and dry weight with control treatment, at different intervals. With increase in incubation temperature of different imazethapyr rates; all growth parameters of mustard except germination, increased, indicating that the increased temperature showed decreased persistence of imazethapyr, with minimum persistence between 35 and 45OC. Whereas trifluralin showed minimum persistence at 25OC and maximum at 15OC as revealed by different growth parameters of oat. In both the herbicides, different growth parameters of test plant decreased with increase in herbicide rate at different temperature incubations pointing that there was increased persistence with increased herbicide rates.