Don’t let your citrus get stressed
Expecting dry & warm weather? Learn when and how much to irrigate
Dry and warm weather conditions are characterized by high Vapor Pressure Deficit (VPD) values (during the day and the night). Insufficient water availability, especially under these extreme weather conditions, may induce plant stress, reducing the obtained yields and fruit quality.
Growing citrus in sandy soils may be beneficial due to optimal aeration conditions in the rootzone, that is required for optimal root activity – including water and nutrients uptake. Consequently, irrigation during the hot and dry summer season should be applied frequently to supply sufficient soil moisture to the plants. on one hand, it is recommended to avoid excessive irrigation that may limit oxygen supply to the plant roots and may decrease roots activity and plant growth. This balance between water and oxygen supply in sandy soils (characterized by low water holding capacity) can be achieved by applying several irrigation pulses at each day.
What the trunk tells us
According to the soil moisture data, up to 5 irrigation pulses were applied every day. However, it seems that irrigation amounts were relatively low since water percolation to the 40cm depth was very limited. As a result, under relatively high VPD values, trunk maximum daily shrinkage (MDS) values increased, and trunk radius decreased (marked by red arrows), indicating plant stress due to too low water amount in the soil profile. After these high VPD events, under lower VPD values, trunk radius increased again (marked by green arrows) and MDS values were lower, representing plant recovery from the induced stress. In addition, these shallow irrigations may increase the risk for salts accumulation in the upper soil.
Salts accumulation in the upper soil profile, (next to the root zone) may be a great concern when citrus plots are intensively irrigated under high evapotranspiration (ET) values. Under such conditions soil salinity may increase and limit the plant’s ability to uptake water. Moreover, salts accumulating in plant tissues, can be toxic and negatively affect plant photosynthetic capability and plant growth. To avoid this problem, it is recommended to periodically apply high irrigation amounts to leach the excessive salts below the root zone.
It can be concluded that synchronous measurements of weather, plant and soil data can assist in better understanding of the plant water needs under dynamic weather conditions and translate this data into actionable irrigation recommendations. Such recommendations can improve the irrigation strategy by applying the right amount of water at the right time to avoid plant stress and optimize the obtained yields.
Oshri Rinot, Agronomist & Soil scientist, PHD, SupPlant