Abstract:

【Objective】The objective of this experiment is to study the effects of different water and nitrogen levels on root growth and a fruit weight of greenhouse muskmelon, to explore the relationships between root growth, single fruit weight and water and nitrogen supply, and to provide a scientific basis for water and reasonable nitrogen application of local greenhouse muskmelon.【Method】According to the environment parameters (light, temperature, humidity, etc.) inside the solar greenhouse, ‘Yi pin tian xia 208’ of muskmelon was chosen as the test cultivar, irrigation application amount was determined by using modified Penman- Monteith equation. A total of 9 treatments were designed. Muskmelon plants were subjected to three irrigation treatments, that wass 70%, 100% and 130% of crop ET_c (Evapotranspiration) and three N levels, including low nitrogen level N₁ (70 kg N·hm^-2), traditional nitrogen level N₂ (130 kg N·hm^-2) and high nitrogen level N₃ (180 kg N·hm^-2). Treatments were completely arranged randomly. A greenhouse muskmelon crop was grown under mulched drip irrigation conditions to investigate the effects of different water and nitrogen levels on root growth, distribution and single fruit weight.【Result】 Most of the total root lengths were concentrated on the 0-30 cm soil layer. Total root length increased slowly as soil layer increased. Total root length, single fruit weight and water use efficiency of muskmelon descended with the rising of irrigation water amount at the same nitrogen level. The highest values of total root length and single fruit weight were observed in W₂N₂, which were 6 625.48 cm and 818.94 g, respectively. Total root length and single fruit weight of muskmelon showed a trend of decreasing after the first increasing with the rising of irrigation water amount at the same nitrogen level. Water use efficiency descended with the rise of irrigation application rate, PFPN descended with the rise of nitrogen application rate. There was a significant relationship between root length with less than 2 mm, root dry weight and yield，and the correlation reached a significant level, the more root growth, the higher yield would increase, reasonable amount of irrigation water and nitrogen fertilizer could promote root system to absorb water and nutrients, thus increasing production.【Conclusion】The change rule of total root length in the depth of root vertical direction could be simulated by the equation y=A(1-B^x), the equation determination coefficient R² reached more than 0.9. The principle component analysis method was used to evaluate the root growth of muskmelon, and the results showed that comprehensive principle component could represent 97.27% total root information, the highest comprehensive evaluation was obtained in W₂N₂. Unreasonable irrigation and nitrogen applications could result in reducing single fruit weight, characteristic parameters of muskmelon root, water use efficiency and partial factor productivity from applied N. It was concluded that the irrigation level W₂ and nitrogen level N₂ could be recommended as the best combination of water and nitrogen, which promoted the root growth, improved single fruit weight, water and nitrogen use efficiency of muskmelon in the muskmelon production under drip irrigation with plastic film mulching in the experimental area.

Key words: muskmelon, solar greenhouse, water and nitrogen coupling, root growth, single fruit weight