Effect of Organic and Synthetic Mulches on Soil Temperature, Nutrient Availability and Yield of Squash

Description of the Study Area

A field experiment was conducted at Central Research Farm, BARI, Gazipur during 2019-2020 and 2020-2021.The experimental site located at the centre of the agro-ecological Zone of Madhupur tract (AEZ-28) at about 24° 23’ N latitude and 90° 07’ E longitude having a means of elevation 8.4 m above sea level. The soils belong to Chhiata series of the Grey terrace soils (Aeric Albaquept) onder the order of Inceptisols in the USDA Soil Taxonomy [8].

Treatments and Experimental Design

There were four treatments i.e.T1: Control, T2: Black polyethylene mulch, T3: white polyethylene mulch and T4: Rice straw mulch. The experiment was laid out in randomized complete block design (RCBD) with 3 replications of each treatment.

Description of the Experimental Materials

The crop was squash used in the experiment and the variety was Bulam house.

Land preparation, fertilizer application and sowing

Experimental land was tilled with power tiller maintaining 6-8 cm depth and made plot size with 2 m x 2 m. In each plot fertilizer was applied at recommended dose i.e. NPKB @ of 230-80-150-0.3 kg ha-1 was used per STB BARC [9]. Cowdung @ 10 tons ha-1was applied during final land preparation. All PB, 1/2 K and 1/5 N was incorporated into soil before sowing. In each plot made two pits with 30cmx30cmx30cm size. Three seeds were sown in a pit on17 December of both 2019 and 2020 and finally kept single plant.

Fertilizer Top Dressing and Intercultural Operations

The rest K was applied 25 days after seed germination and N was top dressed in four equal splits at 20 days interval after germination. After establishment of the seedlings, plants were mulched on 01 January, 2020 and 31 December, 2020 for both years. Irrigations were applied during fertilizer application with two extra irrigations. Two mulching and wedding operations were done.

Soil Sampling and Analysis

The initial and final collected soil samples were dried at room temperature mixed thoroughly, grinded, sieved with a 2 mm sieve and preserved in plastic containers for subsequent laboratory analysis. Soil samples used were then analyzed for SOM, total N and available P. The SOM was determined by wet oxidation [10], total N by a modified Kjeldahl method [11] and total P by using the SnCl2 reduction method [12]. pH was determined through glass electrode pH meter method [13], K and S were determined through NH4OAC method [14] and turbidimetric method Sperber, 1948, respectively. Micronutrients were analyzed using atomic absorption spectrophotometer. Particle size distribution of the initial soil was analyzed by the hydrometer method [12] and the textural class was determined using the USDA texture triangle. The Bulk density of the soil samples were determined by core sampler method [15]. Moisture content was determined by gravimetric method [12]. Field capacity was done though pressure plate method. The initial results of some important soil physical and chemical properties are in Tables 1a & b.

Initial soil physical properties (0-15 cm).

Chemical properties of the initial soil (0-15 cm) Table 1: Physical and chemical properties of the experimental site during December, 2019.

Data Collected

Soil samples for moisture content determination were collected from each plot, from sowing to harvesting of squash according to treatment. Soil temperature was also monitored. Fruits are harvested when they were still tender and of marketable size. The harvesting was started on 01 February 2021. Plant height, number of leaves plant-1, number of fruits plant-1, average fruit weight, fruit length and finally fruit yield.

Weather Data

Monthly weather data was recorded during the crop growing period of 2019-2020 and 2020-2021 and were calculated monthly average weather data tabulated in the Tables 2 & 3.

*In December and March only the crop growing days were considered to calculate average monthly weather components Table 2: Monthly weather data during the crop growing period of 2019-2020.

*In December and March only the crop growing days were considered to calculate average monthly weather components Table 3: Monthly weather data during the crop growing period of 2020-2021.

Data Analysis

After collection of data, it was tabulate in proper form and subjected to statistical analysis with the help of computer package tested with statistics 10.

Plant Height and Number of Leaves Plant-1

White polythene mulch (67.6 cm) significantly gave the highest plant height than all other treatments and lowest plant height was obtained from no mulch plot (51 cm) (Table 4). For leaves plant-1, white polythene mulch is identical to rice straw mulch but significantly higher to black polythene mulch and control. The increase in growth parameters was attributed to optimum temperature absorption through transparent mulch and increasing microbial activity resulting availability of nutrients as compared to control. The changes in soil temperature below PE mulch could be attributed to different manners of passing more sunlight and sunlight transfer to soil and also to heat accumulation during day and loss during night. Similar findings have also been obtained by Dean Ban, et al. [16].

*Significant at P≤0.05 Table 4: Effect of organic and synthetic mulches on growth characters of squash (2020-2021).

Number of Fruits, Average Fruits Weight, Fruits Length and Diameter

Number of fruit and fruit length of squash under mulching were significantly increased (Table 5). Maximum fruit length, number of fruit and fruit diameter was observed in white polyethylene mulch treatment, whereas the minimum was noted in control (Table 5). The highest fruit length under white polyethylene mulch was due to higher soil temperature which might result in higher release of nutrients through mineralization for better growth of fruit, the reduction in evaporation losses of soil moisture caused by mulch cover. The above results were similar with those of Qin, et al. [17], Ansary and Roy [18] in bottle gourd. White polyethylene mulch was found to have significantly better effect on the extent of fruit set than other mulching materials tried. This mulch consistently increased higher fruit set than other mulch and no mulch. White polyethylene mulch might have provided more sunlight to soil and have inhibited escaping of heat finally increase soil temperature and pest- disease control. The present finding was in accordance with Bhardwaj [3] in vine crops like squash, cucumber. It was found that all treatments of mulching material significantly increased the average fruit weight (kg) of squash than control. Among all mulching treatments, maximum average fruit weight was recorded in treatment white polyethylene mulch. It appears that white polyethylene mulch might have induced favourable conditions conducive to attaining fruits with higher weight. The above results were in agreement with those of Aruna, et al. [19] in tomato and Angrej-Ali and Angej [20] in strawberry. It was found that all the treatments of mulching material were significantly increased the fruit yield of squash.

* Significant at P≤0.05 Table 5: Effect of organic and synthetic mulches on yield attributing characters of squash (2020-2021).

Fruits Yield

Among all mulching treatments, maximum fruit yield was recorded in treatment white polyethylene mulch (Table 6) compare to other mulch and no mulch. Plants under polyethylene mulch (white polyethylene mulch) produced higher fruit yield because of better plant growth due to more sunlight, more absorption of soil temperature into soil, more microbial activity and more availability of nutrients. The above results were confirmed with those of Qin, et al. [17] in maize, Hallidri [21] in cucumber, Ibarra, et al. [22] in muskmelon.

* Significant at P≤0.05 Table 6: Effect of organic and synthetic mulches on yield of squash.

Soil Moisture

Mulch prevents soil water evaporation and thus helps retain soil moisture. The amount of moisture stored in the profile to a soil depth of 0-15 cm was significantly greater under black polyethylene over control (Table 7). Black polyethylene conserved the highest soil moisture and it was higher over all other treatments. White transparent sheet and straw mulch were found to be significantly superior over control. The reason for enhanced soil moisture storage under polyethylene and straw mulch may be attributed to significantly lesser evaporation from the soil surface. This study has shown that during December-March, when there is not much rainfall in the area, the soil moisture on the surface and the upper subsoil of un-mulched plots can be reduced from field capacity to wilting point or below, whereas the soil moisture in the mulched plot remains well above the wilting range. The result was in conformity with the findings of Ramakrishna, et al. [23] who reported that the amount of moisture stored in the profile to a soil depth of 90 cm was significantly greater under polythene and straw mulch over bare and chemically mulched soil. Singh and Kamal [24] also reported that black polythene mulch increase soil moisture reserve in soil and inhibits weeds growth

* Significant at P≤0.05 Table 7: Effect of organic and synthetic mulches on soil moisture of squash 2020-2021.

Soil Temperature

A congenial temperature prevailed in the soil covered with black and white mulches for microorganism to remain active throughout the growing season (Table 8). All the mulched treatments had significantly higher temperature (p ≤0.05) at 0-15 cm soil depth compared to control treatment. Mean soil temperature under black polyethyene mulch and straw mulch was lower by 2oC compared to white polyethylene sheet (Table 8). Generally, highest soil temperature was recorded in white polyethylene mulch, followed by control. The prevention of direct contact of solar radiation alongside increased moisture content with the soil by the black polythene mulch and also organic mulches explains the low soil temperature under straw mulch. The high soil temperatures of polythene mulched plots observed in this investigation were in agreement with the results of Tegen, et al. [25]; Bhardwaj [3] & Melek and Atilla [26]. The present investigation shows that the polythene mulch offers better insulation than the other mulches and hence the increase in soil temperature. This employed for production of squash [27].

* Significant at P≤0.05 Table 8: Effect of organic and synthetic mulches on soil temperature of squash 2020-2021.

Physical and Chemical of Post-Harvested Soil (After Two Years)

From the table found that, soil moisture, field capacity and bulk density of different mulches gave positive result compared to initial soil result (Table 9 a). In case of soil chemical properties pH and potassium more or less remain same but others properties were increased compared to initial soil chemical properties (Table 9 b).

Table 9a: Physical properties of post-harvest soil (after two years).

Table 9b: Chemical properties of post-harvest soil (after two years).