In Canterbury we have had one of the best spring early summer periods for a number of years. By one of the best I mean we have had enough rain to availd the need for irrigation. In the last week the pattern has changed.
The current weather forcast on Yr ( check out the Norwegian weather forcast site, one of the best, just Google YR weather ) sows no rain for the next couple of weeks. We are now almost at December, approaching the longest day and with a good hot norwester evapotransporation can get close to 10mm a day. That is the ground with full grass or crop cover can lose 10mm of water a day. even if we are averaging say 6mm a day you will lose nearly 50mm of water per week.
Soil moisture is one of those tricky things that it is easy to know when you have plenty of soil moisture and easy to know when you are in drought. The difficult measurement is measureing the bit between these two states. Objective measure ment is the only way to manage an efficient irrigation system.