Co-Authors:
Klein, I., Institute of Horticulture, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Ireland
Abstract:
Improving nutrient use efficiency can be achieved by applying nutrients when uptake efficiency is at its highest level and by avoiding nutrient leaching by rain and by excessive irrigation. Efficient irrigation is a major factor in nutrient use efficiency. A considerable gap exists today between our scientific knowledge on irrigation and its implementation in everyday practice. A new irrigation controller (CommonSensor), developed and tested in practice, was found to implement an Autonomous Threshold Tension Irrigation (ATTI), whereby the plant itself is activating the irrigation, eliminating the need from the farmer to make any (correct or erroneous) decisions regarding when and how much to irrigate. The autonomous irrigation was found to improve irrigation efficiency and water use efficiency. The new battery operated irrigation controller continuously monitors and records the soil water tension, opens a hydraulic irrigation valve at a pre-set soil water tension (0 to -50 kPa) and controls the depth of irrigation by closing the valve at an appropriate time to control depth of irrigation. The continuous record of soil water tension and the irrigation interval recorded can be plotted for immediate inspection and downloaded for further analysis. The success of the controller, which incorporates a combination of hardware, software and method of operation, has been proved in practice and substantiated by scientific measurements (including in grapes) during the last 4 years. Irrigation experiments were carried out in potted soil-less culture of fig grown in a screen house and in a field irrigation experiments with olive. Simultaneous measurements of soil water tension and photosynthesis in grape and fig showed an absolute correlation (r2 = 0.9384 - 1.000), indicating a direct control of photosynthesis and stomatal conductance by soil water tension. Drainage in potted plants was reduced considerably by irrigation at low soil water tension. Neutron scattering measurements in the olive field experiments showed an integrated water use: initially low volume irrigation by the CommonSensor, until complete depletion of winter soil water and subsequently relying for water consumption solely on the irrigation controller. Neutron scattering measurements showed a complete elimination of drainage in drip irrigation. Elimination of drainage in a heavy yielding 'On' year approximately doubled irrigation efficiency in olive (reduced input by 50%, compared to the recommended rate) when soil water tension was maintained at 0 to -10 kPa. Maintaining soil water tension at 0 to -20 kPa further reduced water use by 75%, indicating a substantial increase in water use efficiency. Olive fruit size was reduced 12% by irrigation at a threshold of -20 kPa, compared to -10 kPa but oil yield increased 6%. Using the CommonSensor irrigation controller, irrigation scheduling and volume of water applied are autonomously regulated by the plant, eliminating errors in irrigation. The autonomous frequency of irrigation by the CommonSensor controller is a function of plant water consumption, the set threshold of soil water tension and the soil water available before the set threshold is reached. The effect of available soil water on the frequency of irrigation is influenced by the irrigation system layout (number of laterals and drippers). Our data and the experience we gained using the new controller indicates that it is almost impossible to predict irrigation needs, even by scientists carrying out all the required measurements, let alone by the farmer using an empirical approach. We found it possible and practical to trigger an autonomous irrigation by the plant. It was found that the autonomous irrigation, using an appropriate technology and method, has a major control on plant performance (growth and potential yield) through maintenance of an accurate and steady threshold of soil water tension.
תפריט נגישות
ניגודיות עדינה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם
