When rainfall or irrigation takes place, may growers expect to see similar increase in moisture in the soil profile. Sometimes this can be substantially less these than the event and growers want to to know why this is happening. There can be several reasons for this:
1.  Compaction- Surface compaction will have a very great affect in the infiltration of the water. It is important to evaluate the site for compaction and to ask the grower about the field history to make sure you don’t accidentally put the probe in a compacted area.
2. Texture and Slope- Both texture and slope will affect infiltration rate. The finer the texture and the greater the slope, the less infiltration you will have. 

3. Cultivation-A conventional tilled field will have considerably less infiltration than a no-till field. It is also important to make sure that if tillage is done on any part of the field, that the same practice next to the probe. Many growers will just raise a wing and by pass tillage around the probe. This isn’t a good idea as the area around the probe is now not representative of the rest of the field.

4. Water in the profile- When water infiltrates into a soil, it replaces the air in the soil profile with water. When all of the air has been replaced, the soil is saturated. It is difficult to get water to infiltrate into a saturated soil. Gravity and capillary action needs to move the water through the profile and create more air space of infiltration to take place. Wet soils often won’t be receptive to additional water application and infiltration.

5. Probe rainfall or irrigation- The only way to determine for sure how much rain fell on  the probe is to have a rain gauge at the probe site. There can be rather large differences between rainfall on the probe itself and even just outside the field. So we have to know for sure what rain is falling on the probe. The same thing for irrigation. Many systems have drops below the canopy and those nozzles are often deflected away from the probe by the canopy and much less water falls directly on the probe site. This unequal distribution pattern is the main reason growers are taking drops off and replacing them with nozzles that stay above the canopy

6. Crop Loss – If the crop has been hailed or damaged by wind, livestock, or animals, the water use will be decreased. Call the grower to find out about the status of the crop around the probe and/or make a field visit to visually see what is going on a round the site.

7. Soil Chemistry – Alkalinity and salinity will have affects on water infiltration. CaCO3, which is present in most irrigation water and some of our more calcareous soils