Log in

Login to your account

Username
Password *
Remember Me

Soil Moisture Monitoring

Water is the key for optimising or maximising plant growth. It is needed in much greater quantities than any other input, carries all the nutrient in solution to the plant leaves for photosynthesis and is instrumental in cooling the leaves so as plant growth is not constrained.

Rainfall is the most variable facet of weather, more so than evapotranspiration (ET). Rainfall alone does not supply sufficient moisture for plant growth and can be a major risk for growers. Irrigation is necessary to supplement soil moisture to optimise production.

Not only is irrigation essential, so is the proper management of the irrigation. Rarely during any growing season on any soil type in any region will irrigation not benefit crop yield and quality Soil moisture monitoring (make this a link to (Soil Moisture Monitoring) is the key to ensuring good irrigation management decisions are made to maximise the benefit of irrigation.

The Irrigation Season

Irrigation can begin in August and not stop until May, a season of 7–8 months. Irrigators must be prepared to start early, finish late and in some seasons not stop in between. Irrigation is a 7-day a week task that simply cannot be missed if production is to be optimised.

How Much Irrigation

This will depend on soil type, daily crop water use and the prevailing weather. These factors are inextricably connected to ensure water is supplied to the crop before it becomes so dry the plants cannot grow at optimum rates. There are two extremes of soil types and local environment:

  1. Shallow stony soils (less than 300mm top soil) have only 20–25mm of readily available moisture in this depth of soil — very little! Often regions with these soils are also prone to the effect of the Northwesterly winds. These winds can have dramatic effects on crop growth, in particular increasing the daily water demand and usage (if well watered) two to three-fold.  These soil types require the most amount of irrigation and are best irrigated frequently (2-5 days) with small amounts (10-20mm).
  2. Deeper soils and those with higher clay content have the most available soil moisture. They require the least amount of irrigation and can be irrigated less frequently than the shallow soils with larger amounts (15-30mm).

Irrigation Management Contacts

Phil Neill
Manager, Irrigation Management
M: 027 457 9863
P: +64 3 341 0970
phil@hydroservices.co.nz

Mark Fitzgibbon
Mid/South Canterbury Area Manager
M: 027 457 0413
P: +64 3 341 0970
mark@hydroservices.co.nz
Job Quantock
North Canterbury Area Manager
M: 027 534 3886
P: +64 3 341 0970
job@hydroservices.co.nz

Melanie Smith
North Island Area Manager
21 Ruahapia Road, RD 2
Hastings 4172
M: 027 444 7349
P: +64 6 873 4045
melanie@hydroservices.co.nz
SCHEDULING ORDER FORM

Please note emailed reports require rainfall and irrigation records emailed to This email address is being protected from spambots. You need JavaScript enabled to view it. and broadband is an advantage.

TERMS AND CONDITIONS: Payment must be made by the 20th of the month following the date of the invoice, unless prior arrangement for extended credit has been made. Interest of 18% will be charged monthly on overdue accounts. Debt collection will be taken at the discretion of HydroServices Limited after 60 days. This cost will be added to your account. Any instructions received by HydroServices from the client for the supply of our services, shall constitute acceptance of the temrs and conditions contained above.

The Effect of Getting Behind

Irrigating farmers are most likely to get behind when irrigation is too late starting and/or during a westerly weather cycle. Starting too late can result in “never catching up” until there is a significant rain. Rainfall only allows a catch up on soil moisture content, yield loss is never caught up.  During windy westerly conditions water use by crops can be as high as 7–8mm, much greater than the ability of the irrigation system to keep up. Once soil moisture drops below the critical deficit (the soil moisture content when plants struggle for water) plant growth is affected. Production will decrease by 0.2–0.3% for every potential mm transpired (the mm/day used before reaching the critical deficit) below critical deficit. For example, pasture production could fall from 70–80kg/ha/day dry matter to 50–55kg/ha/day dry matter in 7-10 days if irrigation is too late or unable to be applied.

Measuring Soil Moisture

HydroServices measures soil moisture to determine irrigation requirements. Soil moisture is measured with a neutron probe and dielectric sensors. These direct measurements remove any assumptions and doubts associated with evapotranspiration models.

To measure with a neutron probe, aluminium access tubes are set into the soil at key locations. Soil moisture is measured on a regular (usually weekly) basis at several depths. The readings from the tubes are averaged to provide an accurate assessment of the soil moisture content in the field or crop. This allows an irrigation management programme to be developed in consultation with the grower.

Dielectric soil moisture sensors are installed at 2-3 depths in a soil profile to provide continuous telemetered soil moisture measurements. The sensors are field calibrated to provide precise measurement.

The soil moisture record is accessed on the HydroServices website with a username and password.

How the measurements are used

For fields or crops monitored using a neutron probe, the amount of moisture in the critical root zone and subsoil layers is plotted in an irrigation management report. The report provided for the grower is;

  • in the form of an easy-to-read graph and is updated weekly or whenever measurements are made, or

  • emailed to the grower during the day measurements are made.

Fields or crops monitored using wireless dielectric sensors, the data is audited and irrigation management advice provided on-line 2-3 times during the week.

Irrigation management aims to keep the moisture between the full and stress points so that there is sufficient moisture for optimum growth. If the moisture falls below the stress point, yield will be decreased and quantity diminished. If irrigation raises soil moisture above the full point, the excess drains through the soil, wasting water and leaching valuable nutrients.

SCHEDULING ORDER FORM

Please note emailed reports require rainfall and irrigation records emailed to This email address is being protected from spambots. You need JavaScript enabled to view it. and broadband is an advantage.

TERMS AND CONDITIONS: Payment must be made by the 20th of the month following the date of the invoice, unless prior arrangement for extended credit has been made. Interest of 18% will be charged monthly on overdue accounts. Debt collection will be taken at the discretion of HydroServices Limited after 60 days. This cost will be added to your account. Any instructions received by HydroServices from the client for the supply of our services, shall constitute acceptance of the temrs and conditions contained above.