EFFECT OF GROWING SUBSTRATE ON YIELD OF RADISH IN NIGERIA UNDER RAINFED AND HAND WATERING CONDITIONS

Radishes (Raphanus sativus L) have high nutritive and medicinal values, and are predominantly cultivated in the temperate regions of the world. With the high malnutrition rate in Nigeria, domesticating radish is necessary. However, despite being successfully cultivated using the hydroponics system with cocopeat substrate in Nigeria, the adaption to the soil type is an important factor to consider. Seeds of three genotypes of radish were grown in cocopeat substrate and topsoil under rainfed and hand watering conditions. The experiment was set up as a 3 (genotypes) by 2 (substrates) by 2 (watering methods) factorial laid in a completely randomized design with three replicates. Data were collected on the plant height, number of leaves, leaf area


INTRODUCTION
Radishes (Raphanus sativus L) belong to the Cruciferae family and are quick and easy to grow (Abdel, 2011).Different varieties of radish exist, with the local red and black varieties predominantly cultivated in Asia where it originated (Abdel, 2011).Radishes are mainly cultivated for the tuber parts which can be eaten raw as salad or cooked; however, it also has several medicinal uses (Bakhsh et al., 2006), with high minerals and vitamins A and C contents (Baloch, 1994).Radish can thrive under temperate and tropical climatic conditions, as well as on different soil types especially under moist rich soils (Bakhsh et al., 2006).However, reports of its production are largely skewed in favor of the temperate climate with low humidity level (Wan & Kang, 2005;Ossai et al., 2020).
In Nigeria, Radish is an exotic vegetable as there are little or no report of its cultivation and consumption.Although, owing to the above nutritive and medicinal characteristics of radish and the rate of malnutrition in Nigeria, there is need to exploit this vegetable for consumption due to its quick rate of production (Ossai et al., 2020).However, being a crop that requires cool climatic conditions for optimum yield, timing of the plant period is required as Nigeria has two main season; the wet and dry.
The predominant farming system operational in Nigeria is the fallow system, and the planting period is timed to the onset of rain (Hula, 2013).Although, for a plant that is being introduced to a new environment, adequate care is given in the planting environment to provide all the necessary soil, water, temperature and nutrient requirements.The soil type and planting substrates in case of hydroponics system plays an important role in making moisture and nutrient available to the plant (Hoang, 2020).However, with the first report of radish production in Nigeria using the hydroponics system using the cocopeat substrate (Ossai et al., 2020), it is important to investigate the growth rate of radish in the natural soil condition of Nigeria in comparison to the cocopeat substrate under a rain-fed and hand watering regime, hence; the objective of this study.

MATERIALS AND METHODS
Seeds of three varieties of radish were sourced from the Soilless Farmlab, Abeokuta, Ogun State, Nigeria.The seeds were raised in a dissolved cocopeat substrate in a hydroponics trough for a week.The cocopeat substrate was purchased in block form from Afri-Agri company, Lagos, Nigeria.The buffered cocopeat blocks were dissolved in water and poured into 12 hydroponics troughs (8 litres capacity with 4 segments of 2 litres each).Also topsoil was dug from a dumping ground, and used to fill 12 troughs.The 1 week old radish seedlings were transplanted into the cocopeat substrates and the topsoil at the rate of 1 plant per segment of the trough.6 of the 12 troughs containing cocopeat and topsoil respectively were kept outside to be irrigated by natural rainfall during the period of the radish growth, while 6 of the troughs containing cocopeat and topsoil respectively were irrigated manually every 3 days interval.Poultry dropping was sourced from Ajayi farm, Ibadan, Nigeria.The poultry manure was allowed to dry for one week, ground into fine particles and liquefied by dissolving 1 g in 1 litre of water over a period of 3 days.The liquefied poultry manure was used in fertigating each plant at a rate of 100 ml per plant every week till harvest.
Experimental design, data collection and statistical analysis: The experiment was 3 varieties (Cherry Red Radish, Cherry Belle Radish and White Icicle Radish) x 2 substrates (cocopeat and topsoil) x 2 watering method (Rainfed and Hand watering) factorial experiment laid in a completely randomized design with four replicates.At bi-weekly intervals, data were taken on the plant height, number of leaves and leave area, while at harvest, the harvested tubers and leaves (fresh biomass) were weighed and recorded.Data collected were analyzed using ANOVA (SAS 9.0 version) and differences in treatment means were separated using least significance differences at 5 % level of significance.

RESULTS AND DISCUSSIONS
The results obtained from this study has shown that the genotypic effect on the plant height, number of leaves at 4 weeks after planting and the tuber weight were significant, while the method of watering the plants had a significant effect on the height of the plants at 2 weeks after planting and the tuber weight respectively (Table 1).
At 4 weeks after planting, the height of the CBR genotype was 13.05±0.31which was significantly taller than CRR (10.95±0.31)and WIR (10.47±0.31)respectively.Also at 4 weeks after planting, the number of leaves produced by the CBR and CRR genotypes was 5.50±0.18respectively, and this was significantly higher than the 4.92±0.18produced by WIR.While the area of the leave produced at 4 weeks after planting was insignificant.However, the weight of the tuber produced by WIR (21.35±3.32)was significantly heavier than CBR (7.97±3.32)and CRR (7.15±3.32)respectively (Table 2).The result obtained on the effect of substrates used in this study on the agronomic and yield parameters was insignificant (Table 3).However, at 2 weeks after planting, the height of the plants grown by watering the plants by hand at 3 days interval (9.16±0.15)was significantly taller than the rainfed plants (7.96±0.15),and the weight of the tubers produced by the hand watered plants (17.79±2.71)was also statistically heavier than the rainfed plants (6.52±2.71),while the watering method was insignificant on the number of leaves produced, the leaf area and leaf weight respectively (Table 4).Radish is grown for two reasons; the tuber part, which is grown for the purposes of salad making, and the leafy part used for medicine (Bakhsh et al., 2006).The agronomic performances of the three genotypes used in this study showed that the three genotypes can be effectively cultivated for the leafy vegetable purposes.However, there is more efficient transfer of photosynthate assimilates (net photosynthetic conversion) from the leaves of WIR genotype to the roots which undergoes secondary enlargement to form the tubers (Evans & Poorter, 2001).Although, cool environment favour tuber formation in radish (Sirtautas et al., 2011), this condition cannot be guaranteed in Nigeria as the climatic conditions is not stable (fluctuation between cold and more of hot weather).This implies that the WIR genotype adapts better to the environmental fluctuations.
The first report of radish production in Nigeria was carried out using the cocopeat substrate effectively (Ossai et al., 2020).However, in this study, the difference in performance of the genotypes in both cocopeat and top soil in terms of the agronomic and yield parameters was insignificant.On the other hand, while simulating the production of radish to the natural environmental condition, where rainfall distribution also varies, the consistent supply of water to the plants every 3 days encourages tuber production than the rainfed system.This is because there are periods the plants will be starved of water in rainfed system due to the plants high rate of evapotranspiration (Wan & Kang, 2005), and the plants will be stressed before regaining its good condition by the reoccurrence of rain.This situation validates the work of Bakhsh et al. (2006) and that stated that radish thrives better in a moist rich soil.

CONCLUSIONS
The nutritive and medicinal components radish makes radish introduction to Nigeria important as majority of the populace are malnourished in many essential nutrients.The results of this study had shown that radish can be effectively grown on the soil type of Nigeria as in cocopeat system.However, the practice of irrigation system is more favorable for the cultivation as rainfall distribution varies and local farmers mostly lack the means to study the weather condition.Thus both the agrometerological and extension agencies will play a vital role in the weather forecasting and dissemination of the weather condition to the local farmers, as this will help the farmers in planning their cropping system to improve their harvest.

Table 1 .
The effects of genotypes, substrates and watering methods and their interactions on the growth and yield of radish

Table 2 .
Growth and yield performance of three varieties of radish in hydroponics and loamy soil Means with the same alphabet down the group are not significantly different from each other at 5 % significance level.LSD: Least Significant Differences, SE: Standard error.TW: Tuber weight and LW: leaf weight.CRR: Cherry Red Radish, CBR: Cherry Belle Radish and WIR: White Icicle Radish.

Table 3 .
Effect of different substrate sources on the growth and yield of radish Means with the same alphabet down the group are not significantly different from each other at 5 % significance level.LSD: Least Significant Differences, SE: Standard error.TW: Tuber weight and LW: leaf weight.

Table 4 .
Effect of different substrate source on the growth and yield of radish in hydroponics system Means with the same alphabet down the group are not significantly different from each other at 5 % significance level.LSD: Least Significant Differences, SE: Standard error.HW: Hand watering, TW: Tuber weight and LW: leaf weight.