Critical period for weed control in field pea

Legume Research, 39 (1) 2016: 86-90 Print ISSN:0250-5371 / Online ISSN:0976-0571 AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com/www.legumeresearch.in Critical period for weed control in field pea Mainpal Singh* 1, Rakesh Kumar, Satish Kumar and Virender Kumar 2 Department of Agronomy, CCS Haryana Agricultural University, Hisar-125 001, India Received: 16-05-2013 Accepted: 16-11-2013 DOI: 10.18805/lr.v0iOF.6787 ABSTRACT Field studies were conducted during 2008-09 and 2009-10 at Hisar, India to assess the effect of weed competition on crop growth and yield of field pea. Weed density increased up to 60 days and then decreased at later stages of crop growth. Seed yield of field pea was decreased by 50% when weeds were allowed to compete for the entire season. The critical period for weed control was 21-63 days in year 1 and 20-70 days in year 2 to achieve 95% of weed-free yield. It is therefore concluded that, to minimize yield loss due to weed competition in field pea, weed control measures should be targeted to avoid weed competition between 20-70 days after sowing. Key words: Critical period, Field pea, Seed yield, Weeds. INTRODUCTION Field pea is one of the most important grain pulse crop of the world. Field peas are of two types based on the consumption: dry peas and green peas. Dry peas are used as split (dal) and besan for various preparation and green pods are used as vegetables. Crop management factors, such as optimum sowing time and method, plant population, weed competition, water and nutrients affect the yield of field pea. Among these, competition due to weeds is important as uncontrolled weed growth has been reported to cause yield reduction 77.2 per cent (Tripathi et al. 2001). Slow initial growth of field pea and wide spacing provide congenial environment for weeds to grow and compete with crop. The weed emergence timing and duration of weed competition has significant effect on crop yield. A few days of early growth by crop relative to weeds give competitive advantage in favor of crop over weeds (Mohler 2001). Therefore, it is important to identify the critical period for weed control (CPWC) so that weed control measures can be targeted during this window to avoid weed competition as part of overall integrated weed management strategy.the CPWC is defined as the critical window during which weed competition with crop is maximum and must be controlled to avoid yield losses. The knowledge of CPWC would be useful in improving weed control by targeting weed control measures at right time (herbicide application and non-chemical methods including in row cultivation). Tripathi et al.(2001) reported the critical period of weed competition from 15-60 days in tendril pea under tarai of Uttaranchal. Kumar et al. (2009) also reported the critical period of crop-weed competition between 30-60 days after sowing in field pea under rainfed subtropical conditions of Kandi belt of Jammu. To our knowledge, there is no information available on CPWC in field pea in plain area of India. Therefore, the present investigation was undertaken to identify the CPWC in field pea to render weed management more effective and economical. MATERIALS AND METHODS A field experiment was conducted during winter season of 2008-09 and 2009-10 at Pulse Research Farm (29º102 N latitude and 75º462 E longitude) of Chaudhary Charan Singh Haryana Agricultural University Hisar, Haryana. The soil of the experimental site was sandy loam in texture, slightly alkaline in reaction (ph 7.85), medium in organic C (0.43%), available N (154 kg ha -1 ) and P (43.5 kg ha -1 ) and high in K (306 kg ha -1 ). To determine CPWC, treatments with increasing duration of weed interference (to estimate beginning of CPWC) and weed-free period (to estimate end of CPWC) were included. The increasing duration of weed interferences treatments were established by allowing weeds to compete with field pea for 20, 40, 60, 80 and 100 days after crop sowing (referred to as weedy plots), after which the plots were kept weed-free until harvest. The increasing duration of weed-free period, was established by keeping the plots weed-free for 20, 40, 60, 80 and 100 days after crop sowing (referred to as weed-free plots) and then *Corresponding authors e-mail: mainpal.mehla@gmail.com. 1 National Agri-food Biotechnology Institute, Industrial Area Phase-8 Mohali. 2 International Maize and Wheat Improvement Center (CIMMYT)-India office, Pusa, New Delhi.

Volume 39 Issue 1 (2016) 87 weeds were allowed to compete for the remainder of the growing season. In addition, season-long weedy check and weed-free check were also included. Weeds were removed as per treatment with the help of hand hoe. The experiment was conducted under naturally occurring weed population in randomize complete block design with three replications. The plot size was 15 m 2. The field pea variety Uttara was planted in rows 30 cm apart using 75 kg seed/ha on 14 November and 4 November during winter 2008-09 and 2009-10, respectively. A basal dose of 20 kg N ha -1 in the form of urea and 40 kg P 2 O 5 ha -1 in the form of diammonium phosphate were applied uniformly to all treatments. Recommended package and practices other than weed control were adopted to grow the experiment crop. The density of individual weeds and total dry weight of weeds were recorded from two randomly selected quadrates (0.25 m -2 ) in each plot at 20 days interval, and weed sample were dried in oven at 60 0 C to constant weight. At crop harvest, plant height, grain yield and yield attributes (number of pods per plant, number of grain per pod, 1000-grain weight) were recorded. Statistical Analysis: Data were subjected to analysis of variance (ANOVA) and treatment means were separated by least significant difference test at P < 0.005.Non-linear regression analysis was done to estimate CPWC.To determine the beginning of CPWC, the logistic equation was fitted to relative yield (% of season-long weed-free period) with the increasing duration of weed interference, whereas to determine the end of CPWC, modified Gompertz equation was fitted to relative yield with increasing length of weedfree period (Knezevic et al. 2002). The Gompetrz equation fitted is defined as:y= a*exp (-exp (-(x-x o )/b)) Where Y is the relative yield, a is the yield asymptote, b and x o are constants and x is the time of weed free period from sowing (days). Logistic equation fitted is defined: asy=a/1+(x/x o ) b Where Y is the relative yield, a and b are constant, x o is point of inflection, x is the time of weedy period from the sowing (days). The yield loss levels of 5 and 10 % were chosen arbitrarily. Curve fitting and parameter estimation was done using statistical package Sigma Plot 8.0. RESULTS AND DISCUSSION Weed density and growth: Predominant weed species in the experiment were: Melilotus indica (38%), Fumaria parviflora 20%), Cornopus didymus (19.5%), Cyprus rotundus (12.5%), Avena ludoviciana (11.5%), Anagalis arvensis (9%), Convolvulus arvensis (6.5%) and Chenopodium album (6.5%). In both years, weed density increased up to and then, a decreasing trend was observed in season-long weedy treatment (Table 1). Tripathi et al. (2001) found the increase in the density of weeds up to in tendril pea. This showed that majority of weeds emerged up to. This might be because of shading effect of taller weeds and crop on the germination of new flush of weeds. At crop harvest, maximum density of weeds was recorded in season-long weedy check treatment, which was significantly higher than all the treatments. As the weedfree duration increased from 20 to 100 days, weed density decreased significantly. Dry weight of weeds was influenced significantly due to crop-weed competition (Table 1). In season-long weedy check treatment, dry weight of weeds increased up to crop harvest. Weed dry weight decreased with the increase in weed-free duration and increased with increase in weedy duration in the crop. At harvest, season-long weedy check treatment had maximum weed dry weight and which decreased with increasing duration of weed free period up to 80 days. However, and further increase in duration of weedfree period had no effect on weed dry weight. Critical period for weed control: Based on the best fitted regression equations (logistic and Gompertz), the window for CPWC was 20-63 days and 20-70 days after field pea sowing in year 1 and 2, respectively at 5% level of acceptable yield loss (AYL) (Fig 1 and 2). This window decreased to 30-53 days and 30-59 days after sowing in year 1 and 2, respectively at 10% level of AYL. These results represent the length of weed control required to protect crop yield from more than a 5 and 10% yield loss. The majority of studies report 2-5% as the maximum AYL. However, it can vary from farmer to farmer subject to economic risks one is willing to take depending on the market price of the crop and the cost of weed control (Knezevic et al. 2002). The parameter estimates of both regression equations are given in Table 2. Crop growth, seed yield and yield attributes: Plant height increased with the increase in duration of weed interference and decreased with the increase in weed-free period in the crop. This was due to severe competition between crop and weed for light and space in plots with increasing duration of weed interference and less in plots with increasing duration of weed-free period which allowed more space available for lateral spreading (Table 3). During both the years, all the yield attributes including number of branches plant -1, pods plant -1, and grains pod -1 were influenced significantly by treatments with different weedy and weedfree periods. Yield attributes increased with increase in weed-free duration and decreased with increase in weedy period. The yield attributes were highest in season-long weed-free period and at par with weed-free for initial 40

88 LEGUME RESEARCH - An International Journal TABLE 1: Effect of crop weed-competition on density (No. m -2 ) and dry matter (g m -2 ) of weeds in field pea 1. Treatments Weed density Weed dry weight At harvest At harvest 2008-09 2009-10 2008-09 2008-09 2008-09 2009-10 2008-09 2009-10 2008-09 2009-10 2008-09 2009-10 Weedy check 5.8 (32.3) 7.9 (62.1) 8.5 (71.8) 1.7 (2.0) 7.3 (51.9) 10.5 (109.8) 1.7 (2.0) 1.8 (2.1) 10.8 (116.1) 11.2 (124.4) 19.6 (382.8) 20.3 (411.9) throughout Weed free 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 2.0 (2.9) 2.7 (6.1) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.45 (1.1) 1.6 (1.5) throughout Weed free up 1.0 (0.0) 1.0 (0.0) 5.1 (25.0) 1.0 (0.0) 5.0 (23.8) 6.6 (42.2) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 18.8 (353.6) 19.4 (375.4) to Weed free up 1.0 (0.0) 1.0 (0.0) 3.6 (12.0) 1.0 (0.0) 4.4 (18.0) 5.7 (31.4) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 9.3 (86.0) 9.7 (92.6) to Weed free up 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 4.0 (15.1) 5.4 (27.7) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 5.5 (29.0) 5.6 (30.3) to Weed free up 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 2.9 (7.4) 4.3 (17.2) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.7 (1.8) 1.8 (2.3) to Weed free up 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.9 (2.4) 2.5 (5.4) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.8 (2.4) 1.9 (2.6) to Weedy up to 5.7 (31.0) 7.9 (61.3) 1.0 (0.0) 1.7 (2.0) 1.0 (0.0) 1.0 (0.0) 1.7 (2.0) 1.8 (2.1) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) Weedy up to 5.6 (30.4) 7.9 (62.2) 1.0 (0.0) 1.7 (1.9) 1.0 (0.0) 1.0 (0.0) 1.7 (1.9) 1.8 (2.2) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) 1.0 (0.0) Weedy up to 5.8 (33.1) 8.0 (62.9) 8.4 (70.2) 1.72 (2.0) 1.0 (0.0) 1.0 (0.0) 1.72 (2.0) 1.8 (2.1) 10.8 (114.8) 11.2 (124.4) 1.0 (0.0) 1.0 (0.0) Weedy up to 5.8 (33.2) 8.0 (62.6) 8.4 (69.8) 1.7 (1.9) 1.0 (0.0) 1.0 (0.0) 1.70 (1.9) 1.8 (2.2) 10.7 (113.3) 11.1 (122.7) 1.0 (0.0) 1.0 (0.0) Weedy up to 5.8 (32.9) 8.1 (64.6) 8.5 (71.1) 1.7 (1.9) 1.0 (0.0) 1.0 (0.0) 1.7 (1.9) 1.8 (2.1) 10.8 (116.3) 11.1 (121.1) 1.0 (0.0) 1.0 (0.0) SEm (±) 0.16 0.22 0.20 0.09 0.09 0.17 0.03 0.03 0.16 0.17 0.16 0.25 CD at 5% 0.46 0.65 0.59 0.03 0.36 0.51 0.09 0.08 0.46 0.51 0.47 0.73 1 Data are x+1 transformed and data in parentheses are original

Volume 39 Issue 1 (2016) 89 TABLE 2: Parameter estimates for the Gompertz and logistic equations 1. Year Gompertz parameters Logistic parameters a b x o R 2 a b x o R 2 2008-09 111.85 37.23-4.70 0.74 101.68 1.64 107.06 0.81 2009-10 108.74 37.87-6.13 0.73 100.72 1.68 107.04 0.82 1 a : yield asymptote (% of season long weed-free field pea); b and x o constants; R 2 coefficient of determination (%). TABLE 3: Effect of crop-weed competition on plant height, yield attributes, grain and straw yield of field pea Treatments Plant height (cm) No of branches plant -1 No of pods plant -1 No of grains pod -1 Grain yield kg ha -1 2008-09 2009-10 2008-09 2009-10 2008-09 2009-10 2008-09 2009-10 2008-09 2009-10 Weedy check 82.67 72.67 1.52 1.44 10.56 10.09 3.11 2.93 1118 1008 Weed free 60.80 55.32 3.04 2.87 19.26 18.89 4.67 4.40 2224 2015 Weed free up to 77.33 70.69 1.67 1.58 11.90 11.42 3.18 2.99 1245 1118 Weed free up to 63.67 57.09 2.67 2.46 17.11 16.45 3.85 3.63 1938 1730 Weed free up to 62.00 56.47 2.84 2.70 18.98 17.63 4.25 4.12 2159 1888 Weed free up to 61. 70 55.99 2.78 2.84 19.28 18.76 4.20 4.39 2235 1954 Weed free up to 61.67 55.83 2.98 2.81 19.34 18.51 4.62 4.36 2246 1995 Weedy up to 61.33 56.21 2.80 2.74 19.22 18.27 4.53 4.27 2215 1946 Weedy up to 63.00 60.31 2.22 2.18 15.65 15.15 4.02 3.78 1783 1656 Weedy up to 69.33 63.39 2.09 2.07 14.47 13.98 3.36 3.17 1624 1456 Weedy up to 72.61 67.00 1.82 1.72 13.47 12.98 3.22 3.04 1423 1277 Weedy up to 76.61 68.67 1.64 1.55 12.50 11.97 3.13 2.95 1179 1058 SEm± 3.79 3.04 0.14 0.17 0.89 1.09 0.31 0.22 107 95 CD at 5% 11.20 8.97 0.42 0.51 2.83 3.21 0.90 0.66 314 280 Relative yield (% of season long weed free) 140 120 100 80 60 40 20 Weedy Weed free 5 % yield loss 10 % yield loss Relative yield (% of season long weed free) Weedy Weed free 0 0 20 40 60 80 100 120 Days after sowing FIG 1: Critical period for weed control in field pea in 2008-09. days or plots kept weedy only for initial 20 days. Yield attributes were adversely affected in plots where weed competition were allowed for longer than initial 20 days. This might be due to the shading effect caused by taller weeds like wild oat which reduced the availability of light FIG 2: Critical period for weed control in field pea in 2009-10. for the photosynthesis and resulted in less number of yield attributes under weedy condition (Vasilakoglou and Dhima 2012). Akhter et al. (2009) also reported decrease in yield attributes of field pea under the reduced photosynthetically active radiation conditions.

90 LEGUME RESEARCH - An International Journal Seed yield was highest in season-long weed free treatment and lowest in season-long weedy check treatment (Table 3). In both years, season-long weed competition caused 50% yield reduction. The reduction in yield was also reported by Tepe et al. (2011). Yield increased significantly with increase in weed-free duration up to 40 days after sowing, and further increase in weed-free duration had no effect on yield. Seed yield of season-long weed-free plots and plots where weed competition was allowed only for initial 20 days were not significantly different. This suggests that weeds did not start competing with crop in the initial 20 days and competition started when weeds were present for longer than 20 days. CONCLUSIONS Based on 2 year study, it was found that presence of weeds during the initial 20 days did not affect seed yield of field pea and when weeds were allowed for longer than 20 days had adverse effect on seed yield. The window for CPWC in field was 20-70 DAS at 5% AYL and 30-53 DAS based on 10% AYL. Therefore, weed control measures should be deployed in such a way that there is minimum crop-weed competition during the window of CPWC. REFERENCES Akhter, N., Rahman, M.M., Hasanuzzaman, M. and Nahar, K. (2009). Plant characters and seed yield of garden pea under different light intensity. Am.-Eur. J. Agron.2: 152 155. Harker, K.N., Blackshaw, R.E. and Clayton, G.W. (2001). Timing weeds removal in field pea (Pisum sativum). Weed Technology. 15: 277-283. Knezevic, S.Z., Evans, S.P., Blankenship, E.E.,Van Acker, R.C. and Lindquist, J.L. (2002). Critical period for weed control: the concept and data analysis. Weed Science50: 773-786. Kumar, A., Sharma, B.C., Nandan, B. and Sharma, K.P. (2009).Crop-weed competition in field pea under rainfed subtropical conditions of Kandi belt of Jammu. Indian J. of Weed Sci. 41(1&2) : 23-26. Mohler, C.L. (2001). Enhancing the competitive ability of crops. In M. Liebman, C. Mohler, and C. Stave reds. Ecological Management of Agricultural weeds. Cambridge: Cambridge University Press. pp. 269-321. Tepe, I., Erman, M., Yarcin, R. and Bukun, B. (2011).Critical period of weed control in chickpea under non-irrigated condition.turk. J. Agric. For. 35 : 525-534. Tripathi, S.S., Singh, R., Singh, S. and Singh, R.K. (2001). Study on crop-weed competition in tendril pea (Pisum sativum L.) under Tarai of Uttaranchal. Indian J. of Weed Sci.33 (1&2) : 46-48. Vasilakoglou, Loannis and Kico Dhima (2012). Leafy and semi-leafless field pea competition with wild oat as affected by weed density. Field Crop Research. 126: 130-136.