Sunday, September 26, 2010

Beetroot 2: How much water does it need?

A second beetroot crop was transplanted the same week as the first one was harvested. This gave the opportunity to evaluate the irrigation in more detail. We had a system to show how much water was going on (the bottle). Now we needed an estimate of how much water the beetroot could use.

Unfortunately we could not find any evaporation data for Maputo, so the usual crop factor x potential evaporation method was going to be difficult. Moreover the beetroot had been planted as one seedling on each dripper, because the wetting patterns were small on this sandy soil. With lines 1 m apart and dripper spaced at 30 cm, this gave just 3.3 plants per square metre. There was a lot of bare soil, making the choice of a crop factor difficult.

So we installed a wetting front detector 30 cm below the drip emitter. In fact wetting front detectors had been installed in the first beetroot crop and the boys had reported that the indicator floats were almost always in the up position. Now we could link the amount of water applied with the response of the detectors.

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