Analysing soil moisture

Transcription

1 /15/2013 In vineyards utilizing the Sentek Enviroscan Probe

2 OVERVIEW This Document is just a brief overview on the benefits of using a soil moisture probe in your daily decision making process in the management of your vineyard. Please note the information your probe generates is greatly affected by many factors inc: SITE SELECTION TYPE OF CROP SOIL TYPE INSTALLATION TECHNIQUE TOPOGRAPHY LOCATION AND ASSOCIATED WEATHER FACTORS THE LOCATION This installation is located in a Shiraz vineyard in the McLaren Vale grape growing region of Sou Australia. ABSTRACT The information outlined in this document is intended to demonstrate how from analyzing soil moisture graphs you can determine different factors including: WATER HOLDING CAPACITIY ON SET OF STRESS SOIL TYPES SOIL DRAINAGE VS CROP WATER USAGE

3 Contents MOISTURE DATA manual vs. continuous... 3 Seasonal comparison... 4 Saturation to stress... 5 Stacked irrigation investigation... 6 Soil classification... 7 Please Note: the information within this document is based on observations only, based on the response of soil moisture in the soil profile. IPV recommends that independent 3 rd party advice is required prior to changing vineyard management strategies.

4 MOISTURE DATA manual vs. continuous The image below shows the same data however the information on the top graph is continuous and shows irrigation events along with the ability to show the Start time, stop time, duration, infiltration rate, active root zone, crop water usage and critical points like onset of stress, full and saturation point. The lower graph is basically a trend only at best it will verify an event and overtime you would pick up stress. In summary the point data provides a more Reactive Management tool hopefully allowing you to avoid making an error again, where Continuous is a Proactive Management tool allowing you to change the outcome in time for the next irrigation or in some cases during the current irrigation.

5 Seasonal comparison THOSE WHO DO NOT REMEMBER THE PAST ARE CONDEMNED TO REPEAT IT. GEORGE SANTAYANA You can start making decisions and changing irrigation strategies from your first few weeks of data however the real power of the technology comes 12 months later. After 12 months you have enough information to set your critical data points like Onset of Stress, Refill Points and Full Points You can also take a snap shot and compare a point in time this year to a previous year this could help greatly in determining when to do strategies like a Flushing Irrigation or estimating how many weeks before you need to apply your first irrigation. After you have a full 6-8 years data there is a good chance that you have an example of each season (Hot Dry, Hot Wet, Cool Dry and Cool Wet) having this information can help greatly in forward planning strategies for the coming or current season.

6 Saturation to stress Knowing at any given time where the moisture levels are in your soil is critical when planning for a heat wave or period of high heat and wind, a large number of vineyards run very tight irrigation schedules in some cases its not so much the availability of water it the ability to deliver it when and where you need to. Knowing at a glance how many days you have before the Onset of Stress can help quickly in providing and distributing water on a priority basis. Maximizing the water efficiency is also critical in ensuring irrigation strategies are effective, the image below shows that over the first 48 hrs that 30-40% of the water is not utilized by the plant but more likely drainage in the profile, by employing strategies like mulching, irrigating with additives that improve water holding characteristics e.g. AquaBoost will keep the water in the root zone which will reduce the need for such regular irrigations. If through monitoring soil moisture and integrating water efficient strategies you can reduce the frequency and duration of irrigation this will intern give you more opportunities to customize irrigation during high demand periods

7 Stacked irrigation investigation This is where all the questions can be investigated and answers generated. In the Stacked view many factors relating to you irrigation, soil types and vines can be examined. Irrigation: The graph below clearly shows when the irrigation started, when it stopped, the duration and how effective it was, a quick look shows that most irrigations made it to the 60cm zone however even with the same duration and interval as the season progressed the penetration reduced. Vines: Looking at the graph you can see at the end of December that there was good root activity in the 80cm Zone however the irrigation strategy was setup for the 0-60cm zone. If you look closely you can clearly see the daily crop water usage as shown in the stepping in the graph the Flat zones show night time little or no water use, the downward slope shows water use. Soil: By looking closely after irrigation is applied you can get a good idea of the soil type by looking at the time frame between when an irrigation event occurs and how long it takes to get to each of the following sensors, the water will move quickly thru sand and very slowly thru clays. (see Soil Classification for more information)

8 Soil classification The best way to determine your soil type, texture and nutrients is by collecting a soil core or soil sample and getting it tested, failing this the Soil moisture graph can tell you allot about the soil type and texture, there are three main factors of the soil moisture graph that can do this. Soil Moisture Level: Looking over a period of time from one irrigation to the next or ideally from summer through to winter and back to summer, we can see what the moisture range is at a given sensor. If you look at the graph below around December 12 th was the first irrigation for the season prior to it you could see that Sensor 1 was holding around 13% moisture if it was really sandy it would possibly be only 3-5% if it was heavy clay 25-30%. Infiltration rate: Once water is applied (providing it s a good installation) the time it takes to move thru the profile is another good indicator of the soil type in this case it took between minutes (based on sample rate) this would suggest it s a sandy loam the water holding and pre irrigation moisture level help validate this further. Soil Drainage rate: After irrigation both the maximum saturation level and the speed in which the water drains from the profile (surrounding the sensor) also helps determine the soil structure. For example a sandy soil would hold a maximum of 6-10% moisture after removing the water source you could expect a level of 4-6 within minutes (depending on the underlying soil profile) likewise a light clay loam could hold as much 25-35% and drain to 20-25% then hold the rest allowing the plant to draw on the water as required.