Automatic Sensor Controlled Drip Irrigation with Four Different Mulches for Tomato and Watermelon Production

Abstract. North Dakota has a climate that can sometimes have an adverse effect on vegetable and fruit productions. Too much or too little water and large temperature swings are the two leading factors affecting vegetable production agriculture. Drip irrigation under mulch is one way to modify these effects by increasing soil temperature and water use efficiency. Soil moisture sensors can be used to control a drip system that will provide irrigation based on plant‘s needs, which results in an optimal soil moisture regime. In this study, a soil moisture sensor-based drip irrigation system under mulches for specialty crops was designed and installed in a field experiment from June 2019 to October 2019 in Fargo, North Dakota. The treatment plots were completely randomized into split-split plots, with vegetable (tomato and watermelon) and irrigation (drip and no drip) as the splits, and three mulches (clear plastic, black plastic, landscape fabric) and no mulch as the treatments. In each treatment, two soil moisture sensors and two soil temperature sensors were installed at 15 and 30 cm to monitor the soil moisture and soil temperature variation throughout the season. The tomato and watermelon numbers, yields, and sizes as well as chemical analysis were measured weekly starting in late July. The results showed that clear plastic and black plastic mulches had an positive impact on soil temperature and soil water potential whereas landscape fabric showed no major impact over the no mulch treatments. For tomato, fruit grown under black plastic mulch with drip irrigation obtained the largest average fruit weight at 201.3 g, but with no major difference in average diameter, which ranged from 67.9 to 70.4 cm. Tomatoes that are grown under clear and black plastics had slightly higher Brix (sugar content), EC, and pH when compared to other treatments. For watermelon, fruit grown under clear plastic mulch with drip irrigation were found to produce on average larger, heavier fruit with an average weight of 8.7 kg, and length of 38.4 cm. Watermelon grown under clear, and black plastics had a slightly higher Brix 9.97%, and 9.75% in comparison to 8.75%, and 9.24% under landscape fabric, and no mulch. No major difference was found in EC, or pH for watermelon on any treatments. This one-year study showed that the mulch and drip irrigation had a positive effect on tomato and watermelon production in North Dakota‘s climate condition.