Articles
THE EFFECT OF WATER SUPPLY ON THE RESPONSE OF ONIONS AND CALABRESE TO STARTER SOLUTIONS
Starter solutions (20 kg/ha N, 60 kg/ha P2O5) placed 3 cm under the drilled seed, increased the early growth of the onions, approximately doubled dry matter 10 weeks after drilling.
This benefit continued until harvest; total bulb yields were 55.7 and 51.2 t/ha with and without starter solution respectively.
In spite of a wetter than average summer, yield increased linearly at a rate of 0.5 t/ha yield per 10 mm of irrigation water (from 48.6 t/ha to 58.2 t/ha). There was an indication that applying starter solution to unirrigated onions went some way to compensating for a lack of water with an effect equivalent to 40 mm of irrigation.
Weather conditions for the calabrese experiment (summer 1994), were dry with only 84% of average rainfall.
The month after transplanting was particularly hot and dry.
The effect of starter solution (5 kg/ha N, 18 kg/ha P2O5, 3 kg/ha K2O placed in the transplanting hole) on final yield were less clear than with onions.
Although there was a marked visual effect, with starter solution treatments producing larger, greener plants within 1 week of transplanting, this effect had disappeared when plants were sampled for dry matter after 6 weeks.
In contrast to the onions, there appeared to be a yield depression from starter solution though only statistically significant at p = 0.15. A possible explanation is that the starter fertilizer treated plants needed to support a larger canopy at the time when water supply could have been limiting in the immediate root zone.
This theory is supported by the fact that there was no yield depression where plants were well irrigated after transplanting.
The response to overall applications of irrigation was large with increases of 0.3 t/ha marketable yield for every 10 mm of water applied over the range of irrigation regimes tested.