Response of muskmelon growth to film covering, drip pipes density and irrigation lower limits in greenhouse

In the facilities agricultural production, different film-covering modes, drip irrigation pipe density and irrigation lower limits would create different soil water and thermal environment to affect crop growth and yield.Therefore, it would be more meaningful to explore and allocate reasonable film-covering modes, drip irrigation pipe density and irrigation lower limits to improve the soil ecological environment and increase agricultural production.In the study, orthogonal experiment was designed to demonstrate the effects of different film-covering modes, drip irrigation pipe density and irrigation lower limits on the muskmelon growth, photosynthetic efficiency, biomass, yield and water use efficiency in greenhouse, and to analyze the relationship between the yield and the plant growth, biomass, and photosynthetic efficiency.The experiment was carried out in a greenhouse in Da Zhai Village of Da Zhai Town, Shaanxi Province during April-July, 2014.The greenhouse is 108 m long (east-west) and 8 m wide (north-south), which is located at longitude 108°08′E and latitude 34°16′N, with an elevation of 521 m.The experiment site has warm and semi-humid monsoons climate, with annual average temperature of 16.3 ℃, annual average rainfall of 535.6 mm, annual average sunshine of 2163 h, and annual average frost-free period of 210 d.In the orthogonal experiment, the film- covering modes had three levels, as full, half and no film-covering (PF, PH, PN).PF was set as that the furrow ridge, inter-row and rows of the cultivated areas were all covered with film.And, the furrow ridge of the cultivated area was covered with film for the PH level.There was no film covering for cultivated area in the PN level.Drip pipe density was divided into three levels: 1) 1 pipe for 1 line (T1) , 1 drip pipe was placed in every plant row, near to the base of the plant; 2) 3 pipes for 4 lines (T3/4), 3 drip pipes were placed into every 4 inter-row spaces with 30 cm separation between drip pipe and plant; 3) 1 pipe for 2 lines (T1/2), 1 drip pipe was placed midway between 2 plant rows with 30 cm separation between drip pipe and plant and 2 plant rows between each drip line.Irrigation lower limit also had three levels, 60%, 70% and 80% of field capacity (L₆₀, L₇₀, L₈₀) corresponding to the upper limits of 65%, 75% and 85%.In the experiment, soil physical indicators, such as the average soil temperature, the soil moisture content range and pH were determined.The muskmelon growth rate of plant height and stem diameter were also measured.And, the evaluation indexes of photosynthesis, as the chlorophyll, photosynthetic rate and leaf area index (LAI), were also determined.Additional, the plant biomass, the melon yield, irrigation amount and IWUE (Irrigation water use efficiency) were also measured.The stepwise regression analysis was used to explore the correlation of these indicators directly to determine the best agronomic measures in greenhouse.The results showed that the PH level could create higher temperature and more uniform distribution of moisture in the root zone soil, therefore this treatment had better root fresh weight, root-top ratio and leaf area index than that with PF and PN level.The PH level also had significantly higher soil urease and phosphatase activities than the PF and PN level.It could enhance the muskmelon's biomass, yield and IWUE in greenhouse.The drip irrigation pipe density had a great influence on melon yield.The fresh weight and dry weight of muskmelon plant under the T3/4 were less than that under T1 and T1/2, but the stem diameter, fresh weight of root and root-top ratio were higher.And T3/4 was benefit for muskmelon to absorb more nutrients and to distribute more photosynthetic products for the fruit, so yield under this treatment had increased by 8.56% and 8.56% respectively than that under T1 and T1/2.The irrigation lower limits was an important factor for muskmelon growth and yield.L₇₀ had made the muskmelon plant growing more balance and increased yield 22.58% and 2.42% than L₆₀ and L₈₀ respectively. IWUE values under PF and PH level were 57.21% and 56.41% higher respectively than the PN level, IWUE of T3/4 was 3.54% and 0.80% higher respectively than that of T1 and T1/2, and the IWUE of L₇₀ was 58.46% higher than that of L₈₀.Therefore, the half film-covering mode (PH), drip irrigation pipe density of 3 pipes for 4 lines (T3/4) and 70% field capacity (L₇₀) would be recommended for melon cultivation in the greenhouse.