The Effect of Weed Control on the Growth and Yield of Shallot (Allium ascalonicum L.)

— Weeds are one of several factors that cause decreased shallot production. Weed control is needed to increase production. The experiments to study the effect of weed control on the growth and yield of shallot had been conducted from June 2019 to September 2019 at Kepuharjo Village in Karangploso Sub- District, Malang Regency. The experiment used a randomized block design (RBD) with 6 treatments and 4 replications. The results showed that for treatment of weed-free, weeding at 15, 30 and 45 DAP (Days after planting), application of oxyfluorfen herbicides at a dose of 1.5 l /ha + weeding at 30 DAP, silver black plastic mulch + weeding at 30 DAP and straw mulch rice + weeding at 30 DAP the dry weight of weed significantly decreased. The growth and yield of shallot showed significantly higher with weed free treatment followed by weeding 15, 30 and 45 DAP, application of oxyfluorfen herbicide at a dose of 1.5 l/ ha + weeding at 30 DAP, silver black plastic mulch + weeding at 30 DAP and rice straw mulch + weeding at 30 DAP treatments. The growth and yield of shallot showed significantly lower with the treatment of without weed control compared with the other weed control treatments .


I. INTRODUCTION
The shallot plant is one of the essential plants in society that functions as a spice for food and traditional medicine, and has been cultivated by farmers for a long time. The need for shallots continues to increase in line with the growing population of Indonesia, which leads to shallots having a quite high economic value. In Indonesia, the consumption of shallots tends to increase with an average growth of 8.31% kg/ capita/ year and shallot production has increased by 3.93%/ year. The increase in production was caused by an increase in harvesting area by 7.16%/ year and productivity by 1.05%/ year (Center for Data and Agriculture and Information System, Ministry of Agriculture, 2016).
Various appropriate cultivation technologies continue to be applied to increase the production of shallot plants. One of the factors that interfere the production of onion family and increase cultivation cost is the presence of weeds around plants (Vijayvergiya, 2018). Onion plants are considered as weak competitors against weeds because of their slow growth, short plant shape, shallow roots system, upright leaves and cylindrical shape making them less able to suppress the growth of weeds through the closure of plant shade (Sekara, et al., 2017). The presence of weeds can reduce crop yields because of competition for growth factors such as water, light, air, nutrients and weed also become host for pests or diseases (Bhullar, et al., 2015). Weed competition with weed can reduce onion bulbs yield by 30 -60% (Tripathi, et al., 2013). Control of weeds on shallots needs to be performed to increase crop yields.

II.
MATERIAL AND METHOD An experiments to study the effect of weed control on the growth and yield of shallot had been conducted from June 2019 to September 2019 at Kepuharjo Village in Karangploso Sub-District, Malang Regency, at an altitude of ± 525 m above sea level and with an averages rainfall of approximately 1000 mm, average daily temperature of 14 0 C and clay-type soil. The experiment used a randomized block design (RBD) consisting of 6 treatments that were repeated 4 times. The treatment of weed control are P0: without weed control, P1: weed free, P2: weeding at 15, 30 and 45 DAP (Days after planting), P3: application of oxyfluorfen herbicide with a dose of 1.5 l /ha + weeding at 30 DAP, P4: silver black plastic mulch + weeding at 30DAP and P5: rice straw mulch + weeding 30 DAP. Tillage was performed by dredging the soil with a hoe 2-3 times until the soil becomes loose. Seedbed for experimental plot were then made with placement of 2.5 m x 1.5 m, seedbed heights of 30-40 cm, the seedbed placed 50 cm apart, and the replications placed 50 cm apart. Seedlings of Tajuk shallot variety were planted with spacing of 15 x 15 cm. The basic fertilizer consists of 250 kg/ ha of SP 36 and 200 kg/ ha of NPK given after planting. At the age of 15 DAP, 200 kg/ ha of NPK fertilizers was given and at the age of 30 DAP, 200 kg/ ha of NPK fertilizers and 150 kg/ha of ZA fertilizer was given. Fertilizing was performed around the rows of shallot plants.Watering was performed every 2-3 days in accordance with plant conditions. Weed control in weedfree treatment was performed every 3-5 days if there are weeds that grew. Weed control with oxyfluorfen herbicide was performed using a hand sprayer at a dose 1.5 l/ ha with a water volume of 500 l/ha. Silver black plastic mulch and rice straw mulch was applied before planting. Silver black plastic mulch was perforated to grow plants. Rice straw mulch was spread with a thickness of approximately 2-3 cm, and the shallots were then planted between rice straw mulch. Weeding according to treatment was performed manually using a sickle or hoe. Observation of weed dry weight, weed control efficiency (WCE) and weed index (WI) as well as the growth and yield of shallots were carried out at 15, 30, 45 and 60 days after planting. The obtained data were analyzed using analysis of variance (F test) with a level of 5% to determine the effect of the treatment. If significant occur, the LSD (Least Significant Difference) test was carried out with a level of 5%.
Weed Control Efficiency (%) Weed control was calculated by using the following formula (Prachand,et al., 2014): (1) Where, WCE = Weed control efficiency (%), DWC = Dry weight of weed in control plot, DWT = Dry weight of weed in treatment plot. Weed Index (%) Weed index was calculated by using the following formula (Prachand,et al., 2014): x 100 (2) Where, X = Weight of bulbs yields in treatment which highest yield, Y = Weight of bulbs yields from the treatment plot.

Weed Growth
Weed control significantly affected the weed dry weight observed at 15, 30, and 60 DAT ( Table 1). The weed dry weight was significantly higher in P0 treatment (without   2017) stated that oxyfluorfen herbicide is widely used by farmers at low doses and is easy to use, both pre and post-emergence and to control annual and perennial broadleaf weeds in a various field crops.

Component of Growth
Plant length did not differ between weed control treatments at 15 and 60 DAP observations and was significantly different at 30 and 45 DAP observations ( Table 2).     (Table 4). At 60 days after planting, the number of tillers in weed-free treatment (4.83 tillers/ plant) did not differ from other weed control treatments (4.00 -5.00 tillers/ plant). The number of tillers was significantly lower in the treatment without weed control (P0) being 3.33 tillers/ plant. For the fresh weight of the bulbs there was no difference among weed control treatments as observed at 15 DAP (

Yield Component
Weed control treatment significantly affected the fresh weight of bulbs/ plants, dry weight of bulbs/ plants, dry weight of bulbs/ harvest plot (0.47 m2) and crop yields/ ha (  IV. CONCLUSION Weed control has a significant effect in controlling weeds and increasing the growth and yield of shallots. With the weed-free treatment, weed dry weight was significantly lower,while plant growth and yield /ha significantly increased. The P2 (weeding at 15 DAP, 30 DAP and 45 DAP), P3 (application of oxyfluorfen herbicide with a dose of 1.5 l /ha + weeding at 30 DAP), P4 (silver black plastic mulch + weeding at 30 DAP) and P5 (rice straw mulch + weeding at 30 DAP) treatments had significant effects in controlling weed growth as well as increasing the growth and yield of shallots compared to without weed control.