Evaluation of irrigation rate and applicability of Penman-Monteith method to bell pepper grown soil regulated by cloud-based automatic fertigation system in greenhouse
2019
Ito, Y. | Yaegashi, S. | Aoki, S. | Kanno, M. | Ozawa, K. | Takesako, H. | Kita, E. | Noborio, K.
In this study, we evaluated the (1) amount of irrigated water by an automatic fertigation system; (2) correlation between atmospheric environment and stemflow; and (3) applicability of Penman-Monteith method to the cultivation soil of three varieties of pepper, viz., Pitaro, Yellow-horn, and Red-horn, in a side-opened greenhouse. The water content in the soil, potential evapotranspiration in the greenhouse, and stemflow in Pi-taro were measured using time-domain reflectometry (TDR), Penman-Monteith method, and stem heat balance method, respectively. Soil water distribution well represented irrigated water by the automatic fertigation system and root distribution. The amount of irrigated water by the automatic fertigation system agreed well with the stemflow rate. There was a significant negative correlation between soil heat flux and stemflow, and significant positive correlation between stemflow and the net radiation, vapor pressure deficit, air temperature, soil temperature, or solar radiation. Potential evapotranspiration in the greenhouse, determined using Penman-Monteith method, increased with increases in the wind speed, temperature, relative humidity, and net radiation, which was consistent with the findings of previous studies. Penman-Monteith method is applicable in a greenhouse setting; however, it is important to consider the size of the greenhouse.
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