Epsilon Archive for Student Projects

Abstract

As the worlds urban population grows more and more every year, it becomes increasingly important that cities become more self-sufficient on food. Indoor vertical hydroponic farms offer a solution to this by placing the farm in an urban environment and growing plants in a controlled environment. Nära Sverige AB is doing just that, by growing kale, pak choi and salad hydroponically in an ebb and flow system, two stories below the ground in Liljeholmen, Stockholm. At Nära Sverige AB, constant seed trials are performed to find new suitable crops for cultivation, with spinach being on top of the list. The yield of hydroponically grown spinach has been found to be higher than field grown spinach. It is also economically sound for a vertical hydroponic system because of its short production cycles. Short production cycles require a uniform emergence of the crop for it to be economically viable. Compared to other crops grown in hydroponic systems, spinach presents a challenge, because of its frequently non-uniform and low seed germination, and germination is highly affected by temperature.
By exploring the effects of different temperatures and water soaking of the seeds on seed germination and juvenile plant growth, this thesis aimed to find the most efficient way of germinating spinach for use in a hydroponic system. This was done in two phases, the germination phase where the aim was to see how the different treatments affected germination percentage, speed of germination and uniformity of germination. And the propagation phase, where the aim was to examine if the different treatments had any lingering effects on the growth and morphology of the plants after a week in the hydroponic system.
Four temperatures were tested, 12, 18, 21 and 27 °C and a soaking treatment was included at 18 °C, the seeds were germinated for seven days and a total of four replicates was performed. After the germination phase half of the seeds were dried and weighed for biomass. The other half were transferred to the hydroponic system for seven days and then measured for height, leaf length, chlorophyll content and biomass.
The results showed highest germination percentage at 12 °C, with decreasing germination rate with increasing temperature. Speed of germination was highest at 27 °C, while the most uniform germination occurred at 12 °C. The soaking treatment had no significant effects on the germination percentage, Temperature had significant effects on plant height, leaf length, chlorophyll content and biomass after propagation. Plant height increased linearly with temperature. Leaf length increased between 12 and 18 °C, before decreasing with temperature.
The most efficient germination method was discussed with the best compromise between high germination, high yield, and uniform growth in mind. Effects on juvenile growth and optimal days of germination were taken into account. Germination temperature of 27 °C showed significantly worse germination percentage, with germination inhibition indicated at 21 °C. Yield inhibition was indicated at 21 °C and above, with decreasing leaf length and chlorophyll content, albeit only significantly at 27 °C.
The high germination percentage, high uniformity, low plant height and favourable effects on juvenile growth all pointed to 12 °C as the most efficient temperature, with six days being the optimal germination time.