Effect of Different Shade Levels on Growth and Yield Performances of Cauliflower

An experiment was conducted during March to July in 2017 (off season) at the Faculty of Agriculture, University of Jaffna, Ariviyal Nagar, Kilinochchi to study the effects of different shade levels on growth and yield performances of cauliflower. Different shade levels such as 25 % (open field), 50 % (single net house) and 75 % (double net house) were used as treatments. The experiment was conducted in completely randomized design (CRD) with four replications. Parametric (growth & yield) analysis were done by using SAS 9.1 package. The influence of environmental variables such as temperature, relative humidity and light intensity were also studied.The result revealed that growing of cauliflower in different shade levels showed great influence on plant growth and yield attributes. There were significant variations in number of leaves, plant height,curd weight, curd diameter and curd circumference of cauliflower under different light intensities. Light intensity in the shade net house was lower than in the open field. The highest vegetative growth and yield were observed in cauliflower which was grown in 50 % shade levels and the lowest yield was in 25 % shade level (open field). It can be concluded that cauliflower can be cultivated in 50 % shade levels successfully to produce quality curd during off season of the dry zone of Sri Lanka.


INTRODUCTION
Agriculture is closely related to the Sri Lanka because of the country's fertility and the different agro climatic zones which are ideal for crop cultivation. The vegetable sub sector is the most important in agricultural sector next to the rice. As with rice, vegetables are grown throughout the country and large numbers of farmers are engaged in this cultivation (Rupasena, 1999). The cool and healthy climatic conditions in the hill country are ideal for temperate vegetable (exotic) crops such as carrot, leek, cabbage, cauliflower, salad leaves, beet, bean, bell pepper and salad cucumber and climatic conditions in the low and mid country are suitable for tropical vegetable crops. Among the exotic vegetables cultivated in Sri Lanka, cauliflower is cultivated in large extent due to its nutritional value and market demand. Cauliflower (Brassica Oleracea Var. botrytis L.) belongs to the family of Brassicaceae originated from Europe and Africa (Ajithkumaret al., 2014). Most daily consumed important vegetable of commercial crop in the world. It also has good demand in Sri Lanka. Consuming cauliflower is useful to fight against cancer,boost heart health,rich in vitamins and mineralsboost brain health,detoxification support and digestive benefits. In cauliflower, the edible curd is made up of abortive flowers. The stalk of cauliflower is short, fleshy and closely crowded (Shanmugavelu, 1989). The growers can cultivate a crop in any season under protected environment, as he can provide the temperature, humidity and light, as required by the plant species. The optimum monthly temperature requirement for cauliflower is 15 to 20 o C with an average maximum of 25 o C and average minimum of 8 o C.Plants require light for optimum growth and development, but the three different aspects of light, quantity, quality and duration, also have a significant influence on growth. A plant under natural conditions receives light from the sun; the amount, quality and duration greatly depend on the season of the year, hour of the day, geographical location and weather. Plants use light as a source of energy for photosynthesis. It is primary metabolites in plants (Kopsell, Kopsell, 2008;Perez-Balibreaet al., 2008). The carbohydrates produced during photosynthesis are stored and used by the plant as a food source. Light intensity can affect plant canopy, flowering, leaf size, and colour in both herbaceous (Jeonget al. 2009;Vendrameet al. 2004) and woody species (Hampson et al. 1996). Sri Lanka is a tropical country and shade nets are used to grow the quality temperate vegetable crops which reduce the crop damages due to heavy rain falls and high solar radiation. In addition, it minimizes the pest and disease damages in many parts of the country. Cultivating the crops under shade nets are needed compulsorily for cultivation of hybrids and some exotic crop varieties because they have are susceptible to extreme external environmental conditions. In net houses, the plant growth and productivity can be manipulated by modifying light quantity (Wheeler, 2008). Cauliflower is highly sensitive to pest attack and it is ideal for cool climate. Therefore, growing of this crop under shade condition is ideal in dry zone of Sri Lanka especially during off season to reduce the effect of light intensity and pest incidence to this crop. There are studies available regarding effect of shade levels on growth and yield performances of cauliflower and other exotic vegetables in the world and few studies are available in Sri Lanka, but none of the study was done in Dry zone of Sri Lanka during off season. To overcome this gap, a research study was carried outwith an objective of evaluating the performance of the cauliflower under different shade levels in Kilinochchi district during off season with the sub objectives of the following, i. To study the effect of different shade levels on morphological characteristics of cauliflower. ii. To study the effect of different shade levels on yield of cauliflower.

II.
MATERIALS AND METHODS A field experiment was carried out at the Faculty of Agriculture, Ariviyal Nagar, Kilinochchiwhich is located at Northern Province of Sri Lankabelongs to the agroecological region of Low Country Dry Zone (DL3) to evaluate the effects of different shade levels on the growth and yield performances of cauliflowerduring the period of March to July 2017. Experiment was conducted in Completely Randomized Design (CRD) with four replications. The cauliflower variety MareetF1 was selected due to its excellent performance in warm conditions. Treatments were  T1 -50 % shade level ( Single net house)  T2 -75 % shade level (Double net house)  T3 -25 % shade level (Open field) For nursery preparation,Seeds were treated with captan and sowed in a nursery tray with dimensions of 22.5 cm in width and52.5 cm in length consisting of cells dimensions of 6.25 × 6.25× 6.25 cm each. Rooting media was prepared by using top soil, compost and cattle manure at the ratio of 1:1:1 and treated with fungicide captan. Three seeds were planted per cell. Cauliflower seeds germinated 2 days after sowing. Three weeks after germination uniform size cauliflower seedlings were planted in 45 cm height and 22 cm width poly bags filled with same rooting media used in the nursery and as 3 seedlings per bag. After the successful establishment of the seedlings, one vigorous healthy seedling was allowed per bag. Cauliflower bags were arranged according to recommended spacing of 60 cm × 45 cm. After planting watering was done by water can and the surface soil was kept in wet condition, but excess watering was avoided. All other management practices were given as recommendation made by Department of Agriculture.The bag arrangements were shown in the plate 1.

Plate 1. Cauliflower under different shade levels
At the time of curd formation, blanching was done in cauliflower. Leaves were tied up with twine to protect the curd from sun burning and browning (Plate 2).

Growth Parameters
Plant height and number of leaves per plant were taken at biweekly interval commencing from 3 weeks after transplanting.

Yield Parameters
The yield components of cauliflower curd such as weight, diameter and circumference were measured during harvesting time.

Data Analysis
The ANOVA was performed by using GLM procedure of the SAS 9.1 computer software package.

III. RESULTS AND DISCUSSION
The results obtained from this research study were discussed in this chapter.

Fig.1: Mean light intensity (klux) from March to June during Experimental period
Mean light intensity was higher in open field condition and maximum light intensity was observed during April than other months (Figure 1). Nangareet al. (2015) reported that shade nets reduced both light intensity and heat effectively during the daytime while changing the spectrum. He also stated that the significant difference was observed in solar radiation in open condition and inside the shade nets.

Number of Leaves
Number of leaves is one of the important growth parameter which influenced by genetic and environmental factors. Leaf is the primary source of photosynthesis. Formation of leaves in cauliflower was significantly influenced by different shade levels.

Fig.2: Number of leaves of cauliflower at biweekly interval
The leaves growth in cauliflower was significantly differed with different shade levels. The highest number of leaf formation was recorded in 50 % shade level and the lowest number of leaves was recorded in 75 % shade level ( Figure  2). This might be due to the favourable effect of 50 % shade net which had increased photosynthetic process in cauliflower due to favourable micro climate.  /dx.doi.org/10.22161/ijeab/3.3.30  ISSN: 2456-1878 www.ijeab.com Page | 952

Mean Curd Weight
The number of days required for curd initiation was influenced due to different shade levels.   intensity were high it promote more growth of curd. Lower shade level gave more volume curds but curds were loosely arranged and not well compacted.

Fig.6: Mean curd circumference of cauliflower
IV. CONCLUSIONS Cauliflower cultivation in Ariviyal Nagar, Kilinochchi was significantly influenced by the season and weather conditions. Growing of cauliflower under different shade levelsshowed great influenced on its growth and yield performance. Numbers of leaves were high in 50 % shade level (single net) than other shade levels. Average plant height of cauliflower increased with increasing shade levels. The highest plant height was in 75 % shade level than other shade levels.The highest mean curd weight and curd diameter were in 50 % shade level than 25 % shade level (open field) condition. Good quality, compact curds were produced at 50 % shade levels than other shade levels. The highest mean curd circumference was in 25 % shade level (open field) than 50 % shade level.

V.
SUGGESTION Other levels of shade and naturally available shade scan also be used as shade level and experiment can be repeated for different varieties in both Maha and Yala seasons to get consistency.