Do You Need to Irrigate Earlier than Expected this Spring?
author By Team Tule, March 28, 2016
Orchard irrigation

Early Season Irrigation Needs for Spring 2016

Even with the recent rainfall, you may need to irrigate in order to hit your target canopy size and achieve your desired yield. With low rainfall in regions such as Lodi, the Central Coast and the San Joaquin Valley, some sites have little water stored in the soil profile and could use early irrigations to meet their production goals for this season. Here’s a look at the early season irrigation needs by region:

2016 Water Year (Oct 1, 2015 to March 15, 2016)
Region Crop Rainfall (inches) Irrigation (inches) Actual ET (inches) Available Water as of 3/15/16 (inches) Target Available Water (inches) Amount Needed Before Bloom (inches)
Central Coast Grape 8.6 1.24 6.87 2.93 6.36 3.46
North Coast Grape 23.56 0.43 6.69 5.38 6.21 1.19
Sacramento Valley Grape 14.03 1.46 6.65 6.25 7.61 1.17
San Joaquin Valley Pistachio 7.96 4.06 7.24 4.13 NA NA
2015 Water Year (Oct 1, 2014 to March 15, 2015)
Region Crop Rainfall (inches) Irrigation (inches) Actual ET (inches)
Central Coast Grape 8.36 3.01 7.23
North Coast Grape 18.77 0.4 5.28
Sacramento Valley Grape 12.28 1.65 6.02
San Joaquin Valley Pistachio 4.9 NA NA
Column summary:
Crop Prevailing crop type of the irrigation and evapotranspiration data collected by Tule in this area.
Rainfall Cumulative rainfall measured by NOAA from from October 1 to March 15 in this area.
Irrigation Average irrigation applied from from October 1 to March 15, as measured by Tule sensors in this area.
Actual ET Average actual evapotranspiration from October 1 to March 15, as measured by Tule sensors in this area.
Available Water The average estimated amount of water in the soil on a given date for fields in this area. It is the sum of the amount of rainfall and irrigation applied minus the actual evapotranspiration. If the calculated amount of water in the soil is greater than the soil water holding capacity, the amount of water in the soil is the soil water holding capacity.
Target Available Water The average amount of water that fields in this area require from budbreak until bloom. For orchards, it is the estimated amount of water required from March 15th, 2016 through April 30th, 2016.
Amount Needed Before Bloom The average amount of water that fields in this area require to reach the Target Available Water quantity. If a specific field has more water than required, the amount needed before bloom for that field is 0. If most fields in an area have sufficient Available Water, but a few have insufficient Available Water, the average Amount Needed Before Bloom is greater than 0.
Calculations:
  1. We calculated the inputs of water to the soil as the sum of the cumulative rainfall in the area and the average applied irrigation in the area from October 1st, 2015 to March 15th, 2016.
  2. We subtracted the outputs of water from the soil as the measured average evapotranspiration from fields in the area over the same period. The water inputs (rainfall and irrigation) minus the water output (evapotranspiration) yields the amount of water in the soil*.
  3. If the calculated amount of water in the soil is greater than the soil water holding capacity for each site, we report the water holding capacity of the soil as the available water for the site. Next, we calculated the average available water in the area.
  4. To determine the Target Available Water, we calculated the regional average spring water use (actual evapotranspiration) for the prevailing crop type (i.e. March 15, 2015 through May 15, 2015 to represent budbreak to bloom in grapes).

*We assumed runoff and deep percolation were negligible for all sites. We did not account for any water applied to fields by another means than the primary irrigation system for the growing season (for example, we didn’t include water applications by sprinkler irrigation for frost control).

Existing Tule users can view site-specific information for your ranch when logged in to the Tule web dashboard. For sites that did not have a Tule sensor installed during the 2015/2016 rain season, click here to look up more local estimates for your ranch and crop type.


Do you want to know if your specific fields are on track to reach their full canopy size this year? Are you interested in knowing how much to irrigate before bloom? Tule customers get all this information and more.

Please Contact Tule Sales for Details