Construction and performance experiment of integrated water and fertilization irrigation recycling system

Abstract: In recent years, horticulture industry has been rapidly developed in China. The total area of cultivation was about 3.79 million ha by the end of 2012, of which 25% was solar greenhouse. But the means of controlling precise water and fertilizer uses are lacking in current solar greenhouse, and the use of water and fertilizers are often excessive resulting in low rate of resource utilization. This not only causes pollutions of environment by excessive fertilizer application and potential runoff/leaching to the surface/ground water systems but also wastes valuable resources. In order to solve the problems, integrated water and fertilization irrigation circulatory system was investigated in this research.Unlike the traditional soil planting pattern in greenhouses from which crops are planted on the ridges of the ground, the newly designed circulatory system was to dig a ditch from south to north in the greenhouse. The width of the ditch was 30-35 cm, and the depth of the ditch was 20-25 cm. There was a 5-10 cm drop from the south to the north. The growth substrate was bagged and then was placed in the ditches. In order to be isolated from the outside soil, the substrate was packed by bags. There were some holes (2 cm, dia.) on the bags so that crops can be planted into the substrate though these holes. There was a soft tube with PVC or PP (2 cm dia.) at the bottom of bags, also it had some other holes (0.2 cm in diameter) through which excess water or nutrient solution can penetrated into the substrate. All of these tubes were connected to a recycle pipe, which led to a drainage tank. The drainage tank was a container which store water or nutrient solution from the recycle pipe, and the horizontal position of drainage tank should be lower than recycle pipe.In order to achieve the recycling, the recycling system of water and nutrient were constructed, a tube of 2 cm diameter with PVC or PP material laying the bottom of substrate bag. A pump was placed in the drainage tank, and the pump was drawn water into a mixing tank until the water level of the drainage tank reaches the set position. The mixing tank contained nutrient solution that was used for irrigation. The water and fertilizers can be mixed according to the desired ratio. The nutrient solution can be adjusted in real time and it was transferred to the crop to provide water and nutrients through irrigation pipes using drip irrigation.An experiment was design to verify the effectiveness of this system. The system was compared with traditional ridge soil planting under the same conditions. The result showed that water consumption of the newly designed recycling system was 69.4% of that in the traditional soil planting pattern. The water use efficiency of the system was 1.92 times higher than that in the traditional soil planting pattern.