EFFECT OF PLANT SPACING AND MULCHING ON GROWTH, YIELD AND QUALITY OF SQUASH

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and (iii)Polythene mulch (M 3 ) in a randomized complete block design (RCBD) with three replications.The variety BARI squash-1 was used in this experiment.The results showed that 1m × 1.5 plant spacing showed significantly the highest yield attributes and quality parameters but 1m × 1 m plant spacing showed significantly the highest yield ha -1 . Polythene mulch showed significantly the highest fruit plant -1 , yield plant -1 and yield ha -1 . Fruit size, individual fruit weight and quality parameter did not show any significant difference irrespective of mulching.The interaction between plant spacing and mulch was significant for yield and quality parameters.Based on the study results it is concluded that maximum yield (50.20 t ha INTRODUCTION Squash (Cucurbita pepo L.) is a cucurbit vegetables crop.It is widely cultivated in the world.This crop is relatively new in Bangladesh, but it is gaining popularity day by day as well as growing in economic significance, both in terms of generating cash and providing nutritional value.It is commonly known as zucchini.It is also known as marrow, courgette, baby marrow, summer squash, bush squash etc. Squash has various health benefits to human as well as medicinal potentials (Mohammad et al., 2011).It contains a variety of vitamins, minerals, amino acids, carbohydrates, and minerals, especially potassium, as well as phenolics, flavonoids, β-carotene, vitamin A, vitamin B 2 , α-tocopherol, vitamin C, and vitamin E. It has various medicinal effects comprising anti-diabetic, anti-hypertensive, anti-tumor, anti-mutagenic, immune modulating, anti-bacterial, anti-hypercholestero-lemic, intestinal antiparasitic, antalgic, and anti-inflammation effects, and utilization possibilities of Cucurbitaceous crops have been reported (Kostalova et al., 2009).
Plant density is an important parameter affecting yield.As a principle, inter-species competition always decreases yield at excessive high populations.However, environmental parameters including light, space, water and soil are not optimally used at excessively low populations and so, the yield decreases (Cormark & Smith, 1998;Rassam et al., 2007).Plants compete on the resources of atmosphere and soil.Optimum plant density depends on different factors such as: the attributes of the plant, growth period, sowing date and method, soil fertility, plant size, available moisture, solar radiation, planting pattern and weeds (Ameri et al., 2007).Optimum plant spacing is one of the major factors in fruitful crop production; it permits plant to grow to their full potential above and under the ground.Optimum spacing also reduces competition between plants for water, sunlight, nutrition and fertilizers.Therefore, plant population can directly or indirectly affect the yield.
Mulches play an important role by reducing soil erosion, improving soil structure, regulating soil temperature, conserving soil moisture and controlling the weed population.Continuous use of organic mulches is also helpful in improving the organic matter content, microbial flora and better soil aeration.Maintaining optimum soil moisture in the root zone of the plants could increase its growth and yield besides conserving precious irrigation water.Mulch is a protective layer that covers the soil's surface and is made up of both organic and inorganic components (Jafarnia and Homayi, 2006).Since the 1960s, plastic mulches have been used commercially to grow vegetables (Lamont, 2005).The application of mulches helped the crop to mature 7-15 days earlier and it also contributed significantly to the plant's height, leaf area index, and dry matter, while the application of plastic mulch treatment improved the yield and efficiency of water usage in comparison to the mulch-free treatments (Zhao et al., 2012).Mulching reduces the deterioration of soil by the way of preventing the runoff and soil loss, minimizes the weed infestation and checks the water evaporation (Kumar and Lal, 2012).Plastic mulch is very popular for its ability to maintain soil moisture (Orzolek and Murphy, 1993).Squash cultivation has a great opportunity in Bangladesh as a quick growing vegetable.There is limited information on how plant spacing and mulch affect summer squash (Cucurbita pepo L.), a newly introduced crop in Bangladesh.So the present study was conducted to find out the effect different plant spacing and mulching on yield and quality of squash in Bangladesh.

Research Location
The research work was conducted at Vegetable Research field of Horticulture Research Centre (HRC), Bangladesh Agricultural Research Institute (BARI), Gazipur, Bangladesh during the period of October 2018 to March 2019.The experimental site is located at 24.0° N latitude and 95.25° E longitude, respectively (UNDP, 1988) at an elevation of 8.4 meters from the sea level (Anon., 1995).Top soil was sandy clay loam in texture having a pH around 6.0.The selected plot was medium high land.Plenty of sunshine and moderately low temperature prevails during experimental period.The weather data during the study period are presented in Table 1.

Experimental Design
The experiment consisted of two factors.Factor A: Plant spacing (3) viz.(i) 1m × 0.8m (S 1 ); (ii) 1m × 1m (S 2 ) and 1m × 1.5m (S 3 ) and (b) Mulch ( 3): (i) No mulch (M 1 ); (ii) Straw mulch (M 2 ) and (iii) polythene mulch (M 3 ).The experiment was conducted in a randomized complete block design (RCBD) with three replications.The variety BARI squash-1 was used in this experiment.The layout of the experiment was prepared for distributing the combination of growing conditions and different planting dates.The 9 treatment combinations of the trail were assigned at arbitrary into 27 plots.The size of each unit plot 3m × 2m (= 6 m 2 ).The distance between block to block 1.0m and plots to plot distance was 0.5m.

Raising of seedlings and crop management
The seeds of BARI Squash-1 were collected from Olericulture Division, Horticulture Research Centre (HRC), BARI, Gazipur.Squash seeds were sown on 28 October 2018 in poly bags at net house of Olericulture division of BARI.Seeds were sown in polybags which were filled with loose friable, dead roots free, sandy loam soil previously mixed with well rotten cowdung.Eighteen days old seedlings were transplanted in the experimental plots.One fourth of cowdung (20 t ha -1 ) and all of gypsum (100 kg ha -1 ) zinc (12.5 kg ha -1 ) and borax (10 kgha -1 ), ½ TSP (175 kg ha -1 ) and 1/3 rd MoP (150 kg ha -1 ) are to be applied, respectively during final land preparation.Cowdung @ 10 kg, TSP @ 60 g, MoP @ 50 g and Magnesium Oxide @ 8 g are to be applied each pit 7-10 days before planting.Urea @ 30 g is to be top dressed each pit at 4 split applications and MoP @ 25g to be applied 10-15 days after planting according to Krishi Projukti Hatboi (BARI, 2015).Healthy and uniform sized 18 days old seedlings were taken from the net house and were transplanted in the main field on 1 November, 2018.Plants were spaced 1m × 0.8m, 1m × 1m, 1m × 1.5m according to treatments.This operation was carried out during late hour of afternoon.The seedlings were watered after transplanting.The insects were controlled successfully by spraying Malathion 57 EC @ 2 ml/L water.The insecticide was sprayed fortnightly from a week after transplanting to a week before first harvesting.Squash fruits were harvested during maturity stage.Harvesting was started from 6 January and completed by 20 February, 2019.Harvesting was done in the morning.The harvested squashes of each plot collect separately, tagged and taken to laboratory for data collection.

Data collection and analysis method
The following data were collected from the experiment

Fruit length:
The length of the fruit was measured with a meter scale in centimeter from the neck of the fruit to the bottom of the fruit.It was measured from each plot and their average was calculated in centimeter.

Fruit diameter:
The diameter of individual fruit was measured in several directions from five selected fruits with slide calipers and the average of all directions was finally recorded and expressed in centimeter (cm).

Individual fruit weight:
From first harvest to last harvest total fruit number was counted and total fruit weight was measured from each plant of each plot to determine individual fruit weight and expressed in kilogram (kg).

Yield plant -1 :
Weight of matured fruits harvested from each picking in the tagged plants in each replication was recorded till final harvest and total yield of fruits per plant computed in kilogram.

Yield ha -1 :
After collection of fruit per plot, it was converted to ton per hectare by the following formula: Plot size (m 2 ) × l 000 kg

TSS:
Total Soluble Solids (TSS) content was determined by a refractometer by placing of drop of pulp on its prism.TSS obtained from direct reading of the refractometer.

Vitamin-C content:
The reagent used for the estimation vitamin C were as follows Five ml of Standard ascorbic solution was taken in conical flask and 5 ml metaphosphoric acid (HPO 3 ) was added to it and shaken.
A micro burette was filled with dye solution then the mixed solution was titrated with dye using phenolphthalein as indicator solution to a pinked coloured end point, which persisted at least for 15 seconds.Dye factor was calculated using to the following formula-0.5

Dye factor = --------Titre
Preparation of sample 10 g of sample was taken and transferred to 250 ml volumetric flask and the volume was made up to the mark with metaphosphoric acid.

Titration
Five ml of metaphosphoric acid extracted sample was taken in an aliquot and titrated with standard dye solution, using phenolphthalein as indicator to a pink coloured end point which persisted at least for 15 seconds.

Virus incidence (%):
Incidence of virus disease recorded during the cropping period.Virus incidence was calculating by counting number of virus infected plants out of total number of plants assessed on two/three dates at 15 days interval, 30 days, 45 days and 60 days after transplanting.Percent data related to virus disease incidence is further subjected to angular transformation.

Number of virus infected plant
Virus incidence Total number of pants assessed

Statistical analysis of data:
The recorded quantitative data were analyzed statistically by using MSTAT-C a computer based program to find out the variation among different treatments, treatment combinations and their interactions.Treatment means were compared by Duncan Multiple Range Test (DMRT).

Effect of plant spacing
The result presented in Table 2 show that significant effect of plant spacing on fruit plant -1 , individual fruit weight, fruit length, yield plant -1 and yield ha -1 .Plant spacing did not play any significant impact on fruit diameter.The maximum number of fruits plant -1 (4.67) was obtained from S 3 (1m × 1.5m) while S 1 (0.8m × 1m) gave minimum number of fruits plant -1 (3.76).Wetzel and Stone (2019) who reported higher fruit number with lower population density.The highest individual fruit weight (1.36 kg) was found from S 3 while the lowest individual fruit weight (1.16 kg) was found from S 2 (1m × 1m).Aniekwe and Anike (2015) also observed similar result with the present sutdy and reported that widest plant spacing resulted higher single fruit weight compared to closest plant spacing.The longest fruit (52.58 cm) was observed from S 3 and shortest (48.77 cm) fruit was found from S 2 .The highest yield plant -1 (6.24 kg) was recorded from S 3 but the highest yield ha -1 (48.40 t) was recorded from S 2 .The lowest yield plant -1 (4.34 kg) was recorded from S 1 and lowest yield ha -1 (42.19 t) was recorded from S 3 .
The result presented in Table 3 show that there was significant effect of plant spacing on total soluble solid (TSS) and vitamin C content.The highest total soluble solid (TSS) (6.01%) and maximum vitamin C content (14.01 mg/100g) was recorded from S 3 and the lowest TSS (5.51%) vitamin C content (12.83 mg/100g) was recorded from S 1 .In a column means having similar letter (s) are statistically identical and those having dissimilar letter (s) differ significantly as per 0.05 level of probability by DMRT.

Effect of mulch
The result presented in Table 4 shows that significant effect of mulching on fruit plant -1 , yield plant -1 and yield ha -1 .Mulching did not differ significantly on individual fruit weight, fruit length and fruit diameter.The maximum number of fruits plant -1 (4.41), highest yield plant -1 (5.24 kg) and yield ha -1 (47.90 t) were found from M 3 (polythene mulch) whereas the minimum number of fruits plant -1 (3.89), lowest yield plant -1 (4.98 kg) and yield ha -1 (44.53 t) were found from M 1 (no mulch).
The result presented in Table 5 showed that there was no significant effect of mulching on total soluble solid (TSS) and vitamin C content.

Interaction effect of growing condition and planting date
Interaction effect of plant spacing and mulch date showed significant effect on fruit plant -1 , individual fruit weight, fruit length, yield plant -1 and yield ha -1 (Table 6) but fruit diameter did not differ any significantvariation.The maximum number of fruits plant -1 (5.0) was found from S 3 M 3 whereas the minimum number of fruits plant -1 (3.53) was found from S 1 M 1 .The highest individual fruit weight (1.43 kg) was observed from S 3 M 3 but the lowest individual fruit weight (1.12 kg) was observed from S 2 M 1 .The longest fruit (52.83 cm) was produced from S 3 M 3 and the shortest fruit (48.07 cm) was produced from S 2 M 2 .The highest yield plant -1 (6.43 kg) was found from S 3 M 3 and the lowest yield plant -1 (4.22 kg) was found from S 1 M 1 .
Although the treatment combination S 3 M 3 gave the highest value of all yield contributing parameters but the maximum yield ha -1 (50.20 t) were observed from S 2 M 3 whereas the minimum yield ha -1 (41.03 t) were observed from S 3 M 1 .It might be due to higher number of plant population.Table 7 presented interaction effect of plant spacing and mulch had significant effect on total soluble solid (TSS) and vitamin C content.The highest total soluble solid (TSS) (6.27%) and maximum vitamin C content (14.10 mg/100 g) were recorded from S 3 M 3 but the lowest TSS (5.40%) and vitamin C content (12.78 mg/100 g) were recorded from S 1 M 1 .

CONCLUSION
From the study, it may be concluded that, yield, quality and yield contributing characters of squash can be effectively manipulated by different plant spacing and mulching.Squash planted 1m × 1.5m with polythene mulch produced significantly the highest number of fruits plant -1 , individual fruit weight, fruit length and yield plant -1 .The highest total soluble solid (%) and vitamin C content (mg/100 g) also found from this treatment combination but the highest yield ha -1 produced from 1m × 1m with polythene mulch due to higher number of plant population.

Table 1 .
Monthly mean weather data during the crop growing periods at BARI, Gazipur Source: Physiology Division, Bangladesh Rice Research Institute, Joydebpur, Gazipur, Bangladesh.

Table 2 .
Yield parameters of squash as influenced by different plant spacing

Table 3 .
Quality parameters regarding TSS and vitamin C content of squash as influenced by different plant spacing

Table 4 .
Yield parameters of squash as influenced by different mulching

Table 5 .
Quality parameters regarding TSS and vitamin C content of squash as influenced by different mulches

Table 6 .
Yield parameters of squash as influenced by different plant spacing and mulch

Table 7 .
Quality parameters regarding TSS and vitamin C content of squash as influenced by different plant spacingand mulchIn a column means having similar letter (s) are statistically identical and those having dissimilar letter (s) differ significantly as per 0.