Three irrigation treatments were set up in northeast China to investigate soil water movement and root water uptake of greenhouse tomatoes, and the collected experimental data were simulated by HYDRUS-2D. The computation and partitioning of evapotranspiration data into soil evaporation and crop transpiration was carried out with the double-crop coefficient method. The HYDRUS-2D model successfully simulated the soil water movement, producing RMSE ranging from 0.014 to 0.027, an MRE ranging from 0.062 to 0.126, and R2 ranging from 79% to 92%, when comparing model simulations with two-year field measurements. Under different water treatments, 83–90% of the total root quantity was concentrated in 0–20 cm soil layer, and the more the water deficit, the more water the deeper roots will absorb to compensate for the lack of water at the surface. The average area of soil water shortage in W1 was 2.08 times that in W2. W3 treatment hardly suffered from water stress. In the model, parameter n had the highest sensitivity compared with parameters α and Ks, and sensitivity ranking was n > Ks > α. This research revealed the relationships between soil, crop and water under drip irrigation of greenhouse tomatoes, and parameter sensitivity analysis could guide the key parameter adjustment and improve the simulation efficiency of the model.
Elucidating the physiological mechanisms underlying crop responses to water and nitrogen availability can help optimize the irrigation and fertilization of greenhouse−cultivated tomatoes. This study aimed to determine how photosynthetic and transpiration characteristics and water use of greenhouse−cultivated tomatoes in Northeast China respond to water and nitrogen treatments under different growth stages. Three irrigation levels (W1−W3) were controlled using the upper and lower irrigation limits, which were 75±5%θfc ,85±5%θfc and 95±5%θfc respectively; and the lower limits were 65±5%θfc, 75±5%θfc and 85±5%θfc respectively (where θfc is the field holding capacity). Three levels of N application were used: N1 (180 kg hm−2 soil), N2 (240 kg hm−2 soil) and N3 (360 kg hm−2 soil). The results showed that tomatoes at flowering and fruiting stage (Stage 1) were not suitable for water deficiency (W1) and high N application (N3), and leaf instantaneous water use efficiency (WUEins) and yield were more significantly correlated. The fruiting stage (Stage 2) was the growth stage with the weakest negative correlation (R2=0.24−0.49) between water use efficiency (leave scale and plant scale) and yield, and the water−nitrogen interaction started to show positive regulation of all indicators in tomato, so it was the best growth stage to appropriately improve water use efficiency and save water. At ripening stage (Stage 3), irrigation water use efficiency (WUEi) and yield were more significantly correlated. N3 supply could compensate or improve photosynthesis, transpiration index and WUE in the early and mid−growth stages. Water and nitrogen had a significant time−scale effect on the correlation between net photosynthetic rate (Pn) and stem flow rate, but the fit results were good (R2=0.92–0.40) for developing their fitting models under various growth stages. The increase in Pn and chlorophyll content (SPAD) under the W2N2 treatment was not accompanied by an excessive increase in transpiration rate (Tr) and stomatal conductance (Gs), and response of Pn to stem flow rate was minimized by the time scale effect (R2=0.90–0.74), and the water use efficiency and yield at all scales at a superior level. As a result, W2N2 is suggested as the best water and nitrogen treatment for use in greenhouse tomatoes in Northeastern China. The findings of this study can serve as a foundation for smart water and nitrogen management strategies for various greenhouse tomato growth stages in Northeastern China.
In order to enlarge and improve the application of phase changing materials (PCM) composite wall in Chinese solar greenhouse (CSG), the effect of thermal parameters on heat storage and release performance of PCM composite wall were systematically and scientifically investigated by available CFD code of commercial software ANSYS-Fluent, which was almost determined by the parameters such as density, thermal conductive, latent heat fusion and specific heat capacity. The numerical simulation was reasonably validated by the experimental result under the same condition, which was conducted by error analysis of interval analysis (IA) method. The result is shown that IA result between numerical simulation and experiment is 0.96, while the numerical simulation of PCM composite wall is significantly accurate and reliable. The maximum temperature of the center point in interior surface is completely dependent on the contrary tendency changing of thermal parameters at heating time, of which is directly proportional to thermal parameters changing at cooling time, except the specific heat capacity. While only the thermal conductivity increasing is benefit for increasing interior surface temperature of PCM composite wall at final cooling time. The effect of solely thermal parameter on the heat storage and release performance changing of PCM composite wall is from strength to weaken: density changing ([Formula: see text]) > thermal conductivity changing ([Formula: see text]) > latent heat fusion of liquid changing ([Formula: see text]) > specific heat capacity changing ([Formula: see text]).
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