Sunday, November 28, 2010

The couve crop: Day 65

Day 65 and the couve harvest is in full swing. The couve are now 60 cm apart (after the ‘thinning harvest’ around day 42) and they are touching within the rows, but not fully covering the inter-row space.

Around day 42 we did some larger irrigations just to get some wetting front detector samples for nitrate analysis (discussed on the last posting). Then we returned to miserly water supply – giving an average of just 0.9 mm per day on the dry side and 1.5 mm per day on the wet side. Have a look at the size of the plants again, and realise that the weather here is pretty warm – reaching 25-35 degrees C most days and no rain. Could it be possible that the soil remained moist with such a little water under such conditions??

The idea was to irrigate the wet side for two hours when the watermark sensor at 20 cm depth reached 10 kPa. This was achieved, but in the process the subsoil (40 cm) started to dry out slightly as well. There was never enough water to reach the detectors at 30 cm .

The dry side was irrigated when the tension at 30 cm reached 20 kPa. This meant there were fewer irrigation events, and the subsoil started to dry dramatically. So clearly the couve was using more than the average supply of 0.9 mm/day, and was mining the soil storage to do so.

No comments: