Productivity augmentation of greengram (Vigna radiata) through weed management

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1 LR-3793 [1-6] Legume Research, Print ISSN: / Online ISSN: AGRICULTURAL RESEARCH COMMUNICATION CENTRE Productivity augmentation of greengram (Vigna radiata) through weed management S.P Singh, R.S Yadav, Amit Kumawat* and R.R Jakhar Agricultural Research Station, Swami Keshwanand Rajasthan Agricultural University, Bikaner , India Received: Accepted: DOI: /LR-3793 ABSTRACT A field experiment was conducted at Research Farm of Agricultural Research Station, Swami Keshwanand Rajasthan Agricultural University, Bikaner during three consecutive kharif season of 2013, 2014 and The experiment comprising ten weeds control treatments consisting of pendamethalin 1000 g/ha (PE), imazethapyr 50g/ha (3-4 leaf stage of crop), imazethapyr 70g/ha (3-4 leaf stage of crop), pendamethalin + imazethapyr 800g/ha (PE), pendamethalin + imazethapyr 900g/ha (PE), pendamethalin + imazethapyr 1000g/ha (PE), imazethapyr + imazamox 60g/ha (3-4 leaf stage of crop), imazethapyr + imazamox 70g/ha (3-4 leaf stage of crop), 2 hand weeding at 20 and 40 DAS and weedy check in randomized block design (RBD) with three replications. Two hand weeding at 20 and 40 DAS was found most effective to control weeds in greengram and recorded lowest weed count and weed dry matter of both broad leaved and grassy weeds. It was also recorded significantly highest branches/pant, leaf area index, total chlorophyll, protein content in seed, pods/plant, seeds/pod and seed, straw and biological yield over other treatments. Among different herbicides, pendamethalin + imazethapyr 800g recorded significantly higher net returns ( 31350/ha) and B:C ratio (2.70). Key words: Greengram, Herbicides, Imazamox, Imazethapyr, Pendamethalin. INTRODUCTION Greengram is one of the major pulse crops in India which is cultivated in arid and semi-arid region. Pulses are main component of cropping systems of hot arid region (Rathore et al. 2009). Generally in agriculture, weeds cause more damage compared to insects, pest and diseases, but due to hidden loss caused by weeds in crop production, it has not drawn much attention of farmers. Heavy weed infestation is recognized as a major bottleneck in realizing its full yield potential. Being a rainfed kharif crop, weed infestation is one of the most important factor of low productivity besides other constraints. Weed management is an important factor for enhancing the productivity of mungbean as weeds compete for nutrients, water, light and space with crop during early growth period. Yield losses in mungbean due to weeds have been estimated to range between 30-50% (Kumar et al. 2004). Weeding and hoeing are common cultural and manual weed management methods for greengram. Manual weeding at optimum stage is difficult, time consuming and expensive due to intermittent rainfall during rainy season and scanty labour. Under such situation, herbicides use with suitable dose remains the pertinent choice for controlling the weeds. Herbicides in isolation, however, are unable to control complete weed infestation because of their selective kill. Their use can be made more effective if one or two herbicides were mixed together to control diversified weed flora. As imazethpyr and pendimethelin has long persistency in soil (Das, 2008) so its residual effect on succeeding crop in a crop sequence is essential before any recommendation to the growers. Thus, an experiment was conducted with an objective to identify new molecules of herbicides in isolation or their mixtures and their residual effect on succeeding mustard. MATERIALS AND METHODS A field study was conducted for two consecutive years during three consecutive kharif season of 2013, 2014 and 2015 at Research farm of Agriculture Research Station, Swami Keshwanand Rajasthan Agricultural University, Bikaner. Ten weed control treatments comprising of pendamethalin 1000 g/ha (PE), imazethapyr 50g/ha (3-4 leaf stage of crop), imazethapyr 70g/ha (3-4 leaf stage of crop), imazethapyr + pendamethalin 800g/ha (PE), imazethapyr + pendamethalin 900g/ha (PE), imazethapyr + pendamethalin 1000g/ha (PE), imazethapyr + imazamox 60g/ha (3-4 leaf stage of crop), imazethapyr + imazamox 70g/ha (3-4 leaf stage of crop), two hand weeding at 20 and 40 DAS and weedy check were evaluated in randomized block design with three replications. The soil of experimental site was loamy sand having 0.08% organic carbon, 8.22 ph, 78, 22 and 210 kg/ha available N, P and K, respectively. Greengram SML-668 was sown on 18 July 2013, 16 July 2014 and 02 July 2015 at 30 cm row to row spacing using seed rate of 20 *Corresponding author s amit.agron@gmail.com

2 2 LEGUME RESEARCH An International Journal kg/ha and was harvested on 10 October 2014 and 08 October 2015, respectively. Recommended dose of fertilizers (20 kg N + 40 kg P + 40 kg K/ha) was applied as basal dose. Preemergence application of pendimethalin and imazethapyr + pendamethalin was done on next day of sowing whereas post emergence application of imazethapyr was done at 25 DAS (3-4 leaf stage) as per the treatment with knapsack sprayer using flat fan nozzle s in 500 litre ha -1 of water. Weed density was recorded by using quadrate of 0.25 m 2 at 60 DAS in all the treatments and then converted into number of weeds/m 2. The weeds were dried in oven till a constant weight was observed and then transformed into g/m 2 by using the appropriate formula. Growth, yield parameters and yield of greengram were recorded for three consecutive years. The data on total weed count and weed dry matter were subjected to square root transformation to normalize their distribution (Gomez and Gomez, 1984). The residual effect of different herbicides applied in greengram was studied on the succeeding mustard. All the recommended package of practices were followed to raise the mustard crop and the crop was irrigated as and when needed. The data on mustard plant population per unit area and seed yield were recorded at the time of maturity. RESULTS AND DISCUSSION Effect on weeds: The experiment field was infested with Amaranthus spinosis L., Digera arvensis Forsk, Trianthema portulacastrum L., Gisekia poredious L., Mollugo verticillata L., Euphorbia hirta L., Aristida depressa L., Portulaca oleracea L., Cenchrus biflorus L., Cleome viscose L., Tribulus terrestris L., Corchorus tridense L., Cyperus rotundus L., Eleusine verticillata L. and Eragrastris tennela L. during the three seasons of experimentation. Herbicidal treatments significantly influenced the population and dry matter production of weeds. The density and dry weight of both broad leaf and grassy weeds were significantly reduced by all weed control treatments compared to weedy check, however, two hand weeding recorded lowest broad leaved, grassy and total weeds compared to rest of the weed control treatments (Table 1). Among the different herbicidal treatments, pre-emergence application of pendamethalin + imazethapyr 1000g as pre sown was found effective in reducing the density and dry weight of both broad leaf and grassy weeds followed by its lower dose (pendamethalin + imazethapyr 800 and 900g/ ha). Application of pendimethalin 1.0 kg/ha as pre sown was found effective against grassy weeds, however, application of imazethapyr 50 g and imazethapyr 70 g were found at par with each other and these treatments significantly reduced the density of broad leaf weeds as comparison to weedy check. Pendimethalin is a versatile pre-emergence herbicide, rapidly absorbed by germinating weeds and inhibit both cell division and cell elongation in the root and shoot meristems of the susceptible plants. The growth is inhibited directly following absorbing through hypocotyls and shoot region. The present results are in close accordance with finding of Yadav et al. (2011). Imazethapyr and imazethapyr + imazamox are selective and applied as post emergence with a view to control late emerging weeds. It inhibits the plastid enzyme acetolactate syntheses (ALS) in plants which catalyses the first step in the biosynthesis of essential branched chain amino acids (Valine, leucine, isoleucine). The ALS inhibitors thus stop cell division and reduce carbohydrate translocation in the susceptible plants (Das, 2008). Saltoni et al. (2004) have suggested that imazethapyr and imazethapyr + imazamox are imidazolinones herbicide, which are absorbed both by the roots and the shoots. These can effectively control a broad spectrum of weeds. Weedy check registered significantly higher number of total weeds. This might be due to effective control of weeds either by manual weeding or herbicides. Reduction in both density and dry weight of grassy weeds with application of imazethapyr + imazamox was might be due to the more effectiveness of imazamox against grassy and thick broad leaved weeds. Hand weedings twice removed the weeds completely and created condition which were more favourable for crop growth and ultimately resulted in lowest density of later emerged weeds and their lowest biomass during the crop growth period. Lower density of weeds by pendamethalin + imazethapyr in reducing weed dry matter might be primarily appeared due to broad spectrum activity of herbicidal combination particularly on establishment of plants of both broad leaf and grassy weeds and its greater efficiency to retard cell division of meristems as a result of which weeds dry rapidly. The results were confirmed by the findings of Kantar et el. (1999), where about 84.6% weed biomass was controlled with application of imazethapyr. Papierniks et al. (2003) also recommended use of imazethapyr in legumes, which inhibit acetohydroxy acid synthase and the synthesis of branched chain amino acids. Effect on greengram: All weed management practices adopted during the experimentation resulted in significant increase in branches per plant. The higher value of number of branches per plant was under treatment two hand weeding, which was at par with pendamethalin + imazethapyr 800, 900 and 1000 g/ha (Table 2). This might have resulted in better availability of moisture and nutrients to the crop in absence of weeds. Moreover increased nutrient and water uptake by crop, which could be increased photosynthate which supply more carbohydrates, resulted in increase cell division and elongation of cells resulted to increase number of branches. The lowest values of number of branches per plant under treatment weedy check might be due to severe competition by weeds for resources, which made the crop plant inefficient to take up more moisture, nutrients and ultimately growth was adversely affected due to less supply of carbohydrates. Similarly, leaf area index, total chlorophyll

3 Table 1: Effect of weed management on weed count and dry weight in greengram Vol. Issue, ()

4 4 LEGUME RESEARCH An International Journal Table 2: Effect of weed management on branches per plant, LAI at 45 DAS, total chlorophyll contents of leaves (mg/g fresh weight of leaf) and protein content (%) in greengram Treatment Branches/plant Leaf Area Index Total chlorophyll Protein content Mean Mean Mean Mean Pendimethalin 1.0 kg Imazethapyr 50g Imazethapyr 70 g Pendimethalin Imazethapyr 800g Pendimethalin Imazethapyr 900g Pendimethalin Imazethapyr 1000g Imazethapyr Imazamox 60g Imazethapyr Imazamox 70g Weed Free Weedy Check SEm± CD( P=0.05) content in leaves and protein content in seed were considerably more in two hand weeding and was at par with pendamethalin + imazethapyr 800, 900 and 1000 g/ha (Table 2). This shows that application of imazethapyr at different doses had no adverse effect on growth of greengram. The higher leaf area index, total chlorophyll and protein content in seed in these treatments might be due to better weed control in these treatments which ultimately increased the yield attributes. The yield attributing characters viz. pods/plant and seeds/pod were significantly improved under various weed control treatments as compared to weedy check (Table 3) and the effect was more pronounced with two hand weeding treatment closely followed by pendamethalin + imazethapyr 800, 900 and 1000 g and pendimethalin 1.0 kg. This was attributed to minimum infestation of weeds together with lesser competition for other growth resources i.e. light, space, water and nutrients. Thus, reduced crop-weed competition resulted into overall improvement in crop growth consequently resulted into better development of reproductive structure and translocation of photosynthates to the sink. The results corroborate with the findings of Yadav et al. (2014). Results showed significant superiority of hand weeding twice treatment over all weed control methods significantly enhanced yield components viz., pods plant -1 and seeds pod -1 with concomitant increased in seed, straw and biological yield. It is an established fact that least crop weed competition during critical phase of crop growth exerts an important regulation function on complex process of yield formation due to better availability of water, space and nutrients to the crop plant. It also helps in improving aeration and nutrient uptake by plant resulting in higher metabolic activity. It was, well emphasized that reduced crop-weed competition under weed free treatment as well as other herbicides, markedly influenced source by virtue of higher photosynthetic and metabolic activity which in turn improved growth of crop and consequently yield components. The adverse effect of weed competition under present investigation is clearly reflected under weedy check, wherein dense population of weeds reduced crop growth compared to two hand weeding treatment as well as other treatments, thus ultimately reduced yield components i.e., pods/plant and seeds/pods. Nutrient stress caused by weeds might have also affected the seed bearing capacity of each pod. Thus, the weeds were able to adversely affect vegetative as well as reproductive parts of crop plant ultimately crop yield. Among different treatments, pendamethalin + imazethapyr 800g/ha recorded higher seed, straw and biological yield over weedy check and was at par with its upper doses and two hand weeding (Table 4). Kantar et al. (1999) also observed 63.6% higher seed yield over unweeded

5 Vol. Issue, () Table 3: Effect of weed management on pods/plant, seeds/pod and test weight of greengram Treatment Pods/plant Seeds/pod Test weight Mean Mean Mean Pendimethalin 1.0 kg Imazethapyr 50g Imazethapyr 70 g Pendimethalin Imazethapyr 800g Pendimethalin Imazethapyr 900g Pendimethalin Imazethapyr 1000g Imazethapyr Imazamox 60g Imazethapyr Imazamox 70g Weed Free Weedy Check SEm± CD (P=0.05) NS NS NS NS Table 4: Effect of weed management on seed, straw and biological yield of greengram Treatment Seed yield (kg/ha) Straw yield (kg/ha) Biological yield (kg/ha) Mean Mean Mean Pendimethalin 1.0 kg Imazethapyr 50g Imazethapyr 70 g Pendimethalin Imazethapyr 800g Pendimethalin Imazethapyr 900g Pendimethalin Imazethapyr 1000g Imazethapyr Imazamox 60g Imazethapyr Imazamox 70g Weed Free Weedy Check SEm± CD (P=0.05) check with application of imazethapyr. The reduced crop weed competition caused significant increase in growth characters and yield ultimately led to higher seed yield of greengram. The significant improvement in seed yield as a result of two hand weeding treatment and all herbicidal weed control treatments could be ascribed to the fact that yield of crop depends on several yield components which are interrelated. Under weedy situation, at early crop growth stage a greater part of resources present in soil and environment are depleted by weeds for their growth. The crop plant thus, faced stress which ultimately affected their growth, development and yield. Like seed yield, straw yield was also significantly increased under various treatments of weed management during the experimentation over weedy check. Increase in straw yield might be due to the direct influence of various weed management treatments on the suppression of weeds. Thus, crop weed competition resulted into increased height, dry matter and branches. The results so obtained for straw corroborate with the findings of Tiwari et al. (2014). Biological yield is a function of seed and straw yield. Thus, significant increase in biological yield with various weed management treatments could be ascribed to the increased seed and straw yield. Economics: All weed control treatments recorded higher net returns and B:C ratio over weedy check (Table 5). While, highest net returns and B:C ratio was obtained with two hand weeding. Among different herbicidal treatments, application of pendamethalin + imazethapyr 800g recorded significantly highest mean net returns (31350/ha) and B:C ratio (2.70) closely followed by its higher doses. Among

6 6 LEGUME RESEARCH An International Journal Table 5: Effect of weed management on economics of greengram Treatment Net return ( /ha) B:C ratio Mean Mean Pendimethalin 1.0 kg Imazethapyr 50g Imazethapyr 70 g Pendimethalin + Imazethapyr 800g Pendimethalin + Imazethapyr 900g Pendimethalin + Imazethapyr 1000g Imazethapyr +Imazamox60g Imazethapyr +Imazamox70g Weed Free Weedy Check SEm± CD (P=0.05) other treatments, imazethapyr + imazemox 60 g/ha resulted in higher net returns (27125/ha) with a B:C ratio of 2.60 despite the higher cost involved. The higher seed yield recorded with this treatment might be responsible for higher net returns. These findings are in close vicinity with those reported by Yadav et al. (2014). CONCLUSION From the present investigation it can be concluded that all weed control treatments are almost equally important in controlling weeds and improving crop yield. Pendamethalin + imazethapyr 800g/ha was superior most with respect to yield, yield attributes and monitory returns. REFERENCES Das T K. (2008). Fate and persistence of herbicides in soil. In: Weed Science basics and application, Gomez K A. and Gomez A A. (1984). Statistical Procedures for Agricultural Research (2 nd Edition). A Wiley-Interscience Publication, John Wiley and Sons, New York, USA pp Kanter F. Elkoca E. and Zengin, H. (1999). Chemical and agronomical weed control in chickpea (Cicer arietium L.) Tropical Journal of Agriculture and Forestry, 23: Kumar R. Thakral S K. and Kumar S. (2004). Response of mungbean (Vigna radiate) to weed control and fertilizer application under different planting system. Indian Journal of Weed Science, 36: 131:132. Papiernik S K. Grieve C.M. Yates S R. and Lesch S M. (2003). Phytotoxic effects of salinity, imazethypyr and chlorimuron on selected weed species. Weed Science, 51: Rathore V S. Singh J P. and Beniwal R K. (2009). Rainfed farming systems of hyper arid north western Rajasthan: An analysis. Annals of Arid Zone, 48 (2): Saltoni N, Shropshire C, Cowan T and Sikkema P Tolerance of black beans (Phaseolus vulgaris) to soil application of S- metalochlor and imazethapyr. Weed Technology, 18: Tiwari V K. Nagre S K. Chandrakar D K. and Sharma M K. (2014). Effect of weed management practices on yield attribution of urdbean under late sown condition: 218. Biennial conference of Indian society of weed science on Emerging challenges in weed management. Directorate of weed science research, Jabalpur. Yadav R S. Singh S P. Sharma V. and Bairwa R C. (2014). Herbicidal weed control in green gram in Arid zone of Rajasthan 9, Biennial conference of Indian society of weed science on Emerging challenges in weed management. Directorate of weed science research, Jabalpur. Yadav S L. Kaushik M K. and Mundra S L. (2011). Effect of weed control practices on weed dry weight, nutrient uptake and yield of clusterbean [Cyamopsis tetragonoloba (L.) Taub.] under rainfed condition. Indian Journal of Weed Science, 43 (1/2):