The Application Of Compound Substrate Of Cassava Residue For Protected Cultivation Of Cucumber

The experiment is conducted to relieve the pressure caused by over-exploitation of the rare substrate raw material-peat moss. In order to find the substrate formula in facility cultivation which is mainly composed by cassava residue, the composted cassava residue is used as the raw material to mix with vermiculite, mushroom residue and peat moss in different volume ratio. The cucumber (Cucumis sativus L.) cultivar of'Lufeng'was planted in pot under simple facility. By comparing the plants'nutritive growth indexes, the photosynthetic traits, the yield and properties of fruits, the suitable substrate to cultivate cucumber came out to be Formula No.1.The proper fertilizing amount of nitrogen and potassium as well as the optimum substrate moisture were also concluded in this experiment. The main results are as follows:1. The bulk density of cassava residue was 0.40 g-cm3, the total porosity was 54.4%, water-holding porosity was 36.9% and the aeration porosity was 17.5%, pH value was 7.54 and the EC value was 1.11 dS-m'1. From which we can see, cassava residue is slightly alkaline and its bulk density and total porosity is low, which makes it need to be mixed with other substrates to cultivate cucumber.2. By mixing cassava residue as the major raw material with peat moss, mushroom residue and vermiculite in different volume ratio, Formula No.1 (cassava residue: vermiculite:peat moss=2:1:1) performed considerable merits in physical properties, with its bulk density of 0.43g-cm-3, total porosity of 65.5%, water-holding porosity of 38.6%, aeration porosity of 26.9%, EC value as 7.80 dS-m-1 and pH value as 6.46. The cultivation results also suggested that Formula No.l would be the most suitable compound substrate.3. When the cassava residue was used as the main substrate to cultivate cucumber, by adding the same amount of phosphate and potassium fertilizer, the results suggested that when adding 15 g nitrogen fertilizer per bucket, the fruiting stage lasted the longest and achieved the highest yield as 25.14 per plot, which was 22.33 kg more than the non-nitrogen fertilizer application treatment, and 87.75% higher than the the treatment of 25 g nitrogen fertilizer per bucket, while the nutritive properties performed best throughout whole the fruiting stage.4. When the cassava residue is used as the main substrate to cultivate cucumber, by adding the same amount of nitrogen and potassium fertilizer, increasing the amount of potassium fertilizer, the growth index, chlorophyll content, photosynthetic efficiency and yield of cucumber all tended to increase first and then decrease; when the amounts of potassium fertilizer was 20 g per bucket, the plot yield of cucumber was the highest, which was 13.98%,15.28% and 35.61% higher than 3 g per bucket,45 g per bucket and 75 g per bucket, respectively.5. Keeping the substrate moisture of Formula No.1 in 95%(±5%) would reach the optimal cultivation results. The results also showed:the chlorophyll content of cucumber leaves would increase with the decrease of substrate moisture, but the photosynthetic efficiency was low, thus the growth of plants was inhibited; when the substrate moisture was low, because of the plant's resistance to adversity, the properties of fruits such as soluble solid, soluble sugar and AsA content, were improved in certain aspects, but the content of nitrate was increased as well which made it no longer edible for health consideration.Above all, the compound substrate made of cassava residue:vermiculite:peat moss=2:1:1(in volume ratio) each pot would be suggested in the cultivation of cucumber, and adding 15 g nitrogen fertilizer and 20 g potassium fertilizer per pot while keeping the substrate moisture in 95%(±5%) would have the best cultivation performance.