A novel dielectric tensiometer enabling precision PID-based irrigation control of polytunnel-grown strawberries in coir
A novel dielectric tensiometer enabling precision PID-based irrigation control of polytunnel-grown strawberries in coir
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DOI：
10.1016/j.biosystemseng.2017.10.018
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发表时间：
2018-01-01
影响因子：
5.1
通讯作者：
Watts, Chris W.
中科院分区：
文献类型：
--
作者：
Goodchild, Martin S.;Jenkins, Malcolm D.;Watts, Chris W.
闭环灌溉控制的好处已在种植者试验中得到证明，这些试验显示了提高作物产量和资源利用率的潜力。通过控制灌溉以响应土壤或基质水分变化来管理用水以满足作物水分需求是一种流行的方法，但需要基质特定的水分传感器校准和导致缺水或过度浇水的水分水平的知识。水张力传感器的使用消除了对基质特定校准的需要，并且能够与水力传导性建立更直接的关系。在本文中，我们提出了一种新的介电张力计，已被设计用于无土基质，如椰壳纤维，泥炭和岩棉与水张力测量范围为-0.7 kPa至-2.5 kPa。这种新的传感器设计也被集成了一个精确的基于PID的（滴灌）灌溉控制器在小规模的椰壳纤维基质草莓生长试验：32草莓植物在4椰壳纤维growbags下的polytunnel。数据表明，可以实现对椰壳纤维中的水张力的出色调节，从而提供稳健且精确的灌溉控制-使水输送与植物的需求相匹配。在30天的生长期内，收集蒸汽压亏缺（VPD）和每日用水数据，并将灌溉控制器设置为将椰壳纤维水张力维持在以下水平：-0.90 kPa、-0.95 kPa和-1 kPa，每个水平至少连续7天。对于每个设定点，通过冲洗控制器将椰壳纤维水张力维持在+/-0.05kPa以内。同时，在试验期间，polytunnel VPD每日从0变化到最大5 kPa。此外，介电张力计和基于PID的灌溉控制的方法相结合，导致日平均VPD和日用水量之间的线性关系超过10天的种植期。(C)2017年IAgRE。由爱思唯尔有限公司出版。保留所有权利。
The benefits of closed-loop irrigation control have been demonstrated in grower trials which show the potential for improved crop yields and resource usage. Managing water use, by controlling irrigation in response to soil or substrate moisture changes, to meet crop water demands is a popular approach but requires substrate specific moisture sensor calibrations and knowledge of the moisture levels that result in water deficit or over watering. The use of water tension sensors removes the need for substrate specific calibration and enables a more direct relationship with hydraulic conductivity. In this paper, we present a novel dielectric tensiometer that has been designed specifically for use in soil free substrates such as coir, peat and Rockwool with a water tension measurement range of -0.7 kPa to -2.5 kPa. This new sensor design has also been integrated with a precision PID-based (drip) irrigation controller in a small-scale coir substrate strawberry growing trial: 32 strawberry plants in 4 coir growbags under a polytunnel. The data illustrates that excellent regulation of water tension in coir can be achieved which delivers robust and precise irrigation control- matching water delivery to the demands of the plants. During a 30-day growing period vapour pressure deficit (VPD) and daily water use data was collected and the irrigation controller set to maintain coir water tension at the following levels: -0.90 kPa, -0.95 kPa and -1 kPa for at least 7 consecutive days at each level. For each set point the coir water tension was maintained by the irrigation controller to within +/- 0.05 kPa. Meanwhile the polytunnel VPD varied diurnally from 0 to a maximum of 5 kPa over the trial period. Furthermore, the combination of the dielectric tensiometer and the method of PID-based irrigation control resulted in a linear relationship between daily average VPD and daily water use over 10 days during the cropping period. (C) 2017 IAgrE. Published by Elsevier Ltd. All rights reserved.