Cost Benefit Analysis of Growing Cucumbers in Greenhouse at Different Cooling of Nutrient Solution Temperatures in Closed Hydroponic System in Oman

Oman is a country that is mostly dry and hot, with daily maximum temperatures easily reaching 40°C or more during summer. The Oman weather therefore renders conventional open field agriculture almost impossible. The sustainable future of agriculture in Oman and other similar desert countries will therefore depend very much on the adoption of land and water saving technologies such as greenhouses and soilless culture or hydroponics. Soilless culture (Hydroponics) is the technique of growing plants without soil with their roots immersed in nutrient solution. Among factors affecting hydroponic production systems, is the nutrient solution temperature which is considered to be one of the most important determining factors of crop yield and quality. The aim of this research is therefore to investigate the economic effect of cooling nutrient solutions temperature technique on cucumber output. Four nutrient solutions temperatures are investigated and a Cost Benefit Analysis is undertaken. Results indicate that all the four cooling nutrient temperature yields positive returns (benefits) above variable and total costs for the two years of this experiment. Cooling nutrient temperature (22oC) yields higher returns than the other treatments followed by treatment (25oC), (28oC) and then the CONTROL treatment. Returns for the second year are higher than the first year. Therefore treatment (22oC) was observed to be the best overall producing the highest return above variable and total costs. It is therefore considered the best alternative for cucumber growers.


Introduction and Background
Cucumber cultivation in greenhouses currently plays a very important role in Oman and other desert countries.In fact, this will continue to be so, as vegetable growing in a controlled environment continues to expand in these countries.This is because one of the most serious constrains facing agriculture in Oman and other desert countries include shortage of land and suitable water for agriculture.Oman is a country that is mostly dry and hot, with daily maximum temperatures temperature easily reaching 40°C or more during summer.Winters are cooler with occasional rainfalls.However, in spring and summer seasons a hot, and dusty wind (the Shamal), blows making it very hot and unbearable.To overcome this, farmers have historically resorted to digging wells and pumping water in order to carry out farming.With time, this has however proved to be unsustainable and destructive because it has resulted into sea water intrusion and hence soil salinity especially in the Batinah coast.The Oman weather therefore renders conventional open field agriculture almost impossible.As highlighted in Mbaga (2013;2014) and (Mbaga et al., 2018) as well as by a number of other authors on this subject matter, the sustainable future of agriculture in Oman and other similar desert countries will depend very much on the adoption of land and water saving technologies such as greenhouses and soilless culture or hydroponics.Soilless culture (Hydroponics) is the technique of growing plants without soil with their roots immersed in nutrient solution (Maharana and Koul, 2011).Among factors affecting hydroponic production systems, is the nutrient solution temperature which is considered to be one of the most important determining factors of crop yield and quality.The temperature of the nutrient solution influences the uptake of water and nutrients differentially by the crop (Maharana and Koul, 2011).There are a wide range of research works done over the years on the combinations of these technologies with very promising results e.g., Al-Helal, (2007);Al-Helal and Al-Hamdan, (2009);Al-Ismaili and Jayasuriya, (2016) and Al-Ismaili et al., (2018).Farmers using hydroponic system in greenhouses to grow vegetables in Oman face the challenge of high temperature of nutrient solution in feeding tanks especially in summer season when temperatures reach above 40 degrees centigrade.The aim of this research work is therefore to investigate the economic effect of cooling nutrient solutions temperature technique on cucumber output.The four nutrient solutions temperatures are: (i) Treatment 1 (22 º C), (ii) Treatment 2 (25 º C), (iii) Treatment 3 (28 º C) and (iv) Treatment 4 (33º C) as CONTROL.

Materials and Methods.
The experiments were conducted in a cooled greenhouse of dimension 30 m long x 9 m wide at the Directorate General of Agriculture and Livestock Research in Rumais, Barka around 40 km north of capital Muscat during three periods of growing cucumber under hydroponics viz., summer temperature period (June-August), fall temperature period (September-November) and spring temperature period (February-May) for two years during 2016/ 2017and 2017/2018.We investigate the economic effect on cucumber output at three Root-Zone Temperatures (Hereafter RZT) of cooling nutrient solution viz.RZT1 (22 ᵒ C), RZT2 (25 ᵒ C) and RZT3 (28 ᵒ C).Besides the three RZT we have the control-uncooled nutrient solution RZT4 (33ᵒC) that had root-zone ambient temperature of over 33 ᵒ C. The experiment was arranged in Randomized Complete Design (RCD) with four replications.Each temperature treatment was equipped with cooling system connected with electricity meter in order to record the power consumption during the course of the experiment.Appendices I and II present raw data in terms of cost of materials (cooling system and stock solution), labour, power consumption per treatment and cucumber output (yield kg/GH) for each of the three cropping period (June-August, September-November and February-May) in a year.The experiment was carried out over a period of two years 2016/2017 (Appendix I) and 2017/2018 (Appendix II).In both years 1 and 2 cucumber price was high during cropping period (June-August) at 0.400 Baiza, as compared to 0.200 Baiza for September-November and February-May cropping periods.Greenhouse Investment Costs (Fixed Costs) for Cucumber Production for this experiment is as indicated in Table1 below.As in other similar studies such as : Smith et.al. 1990;Sengar, and Kothari, (2008); and Chito, (2007) we assume here that contract labor is used to construct the greenhouse.Straight line depreciation approach is used on all items.The depreciation period for each item is as shown in Table 1.An interest charge of 9% is made to the average investment (half the initial cost) of each item as in previous studies above.Taxes and insurance are assumed to be 1.25% of the original investment.

Results and Discussion
Based on the data presented in Appendix I and Appendix II, the variable costs associated with each of the four (4) treatments RZT (22 ᵒ C), RZT (25 ᵒ C), RZT (28 ᵒ C) and the control RZT (33ᵒC) were calculated for the two years for which this experiment was undertaken.The results are as presented in As indicated in Table 3 above results for this experiment in the second year produced a comparable pattern in that the Total Variable Costs for RZT (22º C) were the highest and the Total Variable Costs for RZT (33º C) were the lowest.Similarly, RZT (22º C) consumed more power than the other three treatments.
Table 4. Seasonal and Annual Revenue per Treatment Year One four (4) Treatments.
The results of the analysis of the costs and benefits of the four (4) treatments across the three seasons and over the two years of this experiment are as presented in Table 6 and 7 below.As indicated in the last two rows of Table 6 and 7, all the returns above variable costs and returns above total costs for the two years of this experiment are positive and significantly high.Treatment RZT (22º C) yields highest returns than the other three treatments.This is followed by treatment 2, 3 and then the CONTROL treatment.Returns for the second year are higher than the first year.Table 8 above presents a summary of returns above total costs in Oman rials per treatment for the two years.As can be observed in Table 8 above all treatments across all the two years of this experiment yielded positive returns above total costs.Furthermore, RZT (22º C) was observed to be the best of all producing the highest return above total costs of RO. 3,792.53during the first year and RO. 4, 810.63 during the second year respectively.This means that cooling nutrient solution to a Root-Zone Temperature of 22 ᵒ C (RZT 22 ᵒ C) leads to a better economic effect on cucumber output and hence higher return for cucumber farmers.

Conclusion
Cucumber cultivation in greenhouses currently plays a very important role in Oman and will continue to do so, as vegetable growing in a controlled environment continue to expand in this country.Because of the shortage of land and water, the success of agriculture in Oman depends very much on the adoption of land and water saving technologies such as greenhouses and soilless culture or hydroponics.Among factors affecting hydroponic production systems, is the nutrient solution temperature which is considered to be one of the most important determining factors of crop yield and quality.In this research we conduct the Cost Benefit Analysis of growing Cucumbers in greenhouses at different cooling temperature of nutrient solution in a closed hydroponic system.The four nutrient solutions temperatures investigated are: (i) RZT (22º C), (ii) RZT (25º C), (iii) RZT (28º C) and (iv) RZT (33º C) as CONTROL.
Results showed that all four cooling nutrient temperature yielded positive returns (benefits) above variable and total costs for the two years of this experiment.RZT (22º C) yields highest returns than the other.This is followed by treatment 2, 3 and then the CONTROL treatment.Returns for the second year are higher than the first year.Therefore, RZT (22º C) was observed to be the best of all producing the highest return above variable and total costs of RO. 3,970.29 and 3,792.53during the first year and RO. 4,988.39 and RO. 4,810.63 during the second year respectively.
At this juncture, pending further experiments at the farm level (Farmer's field) at different regions of the country, results obtained here suggests that cooling solutions at 22 degree centigrade (22º C) should be adopted by farmers in Oman as it leads to increased yield and hence more benefits to farmers.

Table 1 .
Greenhouse Investment Costs (Fixed Costs) for Cucumber Production in OmanAs presented on Table1above the construction costs of a cooled greenhouse of dimension 30 m long x 9 m wide used for this experiment amounted to RO 651.500.The depreciation costs are RO130.300,Interestcharges are RO29.318,Taxand Insurance costs are RO8.144 and Annual maintenance costs are RO10.00.As a result, the annualized costs (amount to be charged each year on the enterprise in relation to initial investment costs) areRO.177.761.

Table 2 .
Total Variable Costs per Treatment Year One

Table 3 .
Total Variable Costs per Treatment Year Two

Table 6 .
Return Above Total and Variable Costs in Oman Rial per Treatment Year One

Table 7 .
Return Above Total and Variable Costs in Oman Rial per Treatment Year Two

Table 8 .
Return Above Total Costs in Oman Rial per Treatment for Year One and Two