Mineral Nutrition of Chinese Waterchestnut (Eleocharis dulcis (Burm. F.) Hensch)
Volker Kleinhenz and David Midmore
Central Queensland University
Recently, there has been considerable interest in Australia in the commercial production of Chinese waterchestnuts for import substitution and export. However, Australian growers face problems with the quality of their produce which may be improved by nutrient management. Yet, little information is available on nutrient demand and fertilisation of Chinese waterchestnuts.
The effect of different rates (0-600 kg/ha) of N, P K and form (KCl and K2SO4) of K on nutrient absorption, quality and yield of this aquatic vegetable grown in nutrient solution was studied at Central Queensland University, Rockhampton.
Results show antagonistic and synergistic interactions between uptake of NH4 and PO4. Absorption of NH4 was inhibited at the highest levels of applied N and P (600 kg/ha) as indicated by high residual ammonium in the floodwater. This may be due to oversupply of N not required for metabolism and ion-competition during absorption. Uptake of PO4 required a minimum of N 200 kg N/ha). When no N was applied, PO4 accumulated in the floodwater whereas at the high N rate, PO4 was completely absorbed.
No interactions between K and other nutrients could be found pointing to the high demand for this nutrient. However, the sulphate in K2SO4 affected absorption of PO4 and K. Uptake of PO4 decreased with increasing rates of applied SO4. The K from K2SO4 was initially more slowly absorbed than from KCl but total uptake was greater.
The effects of nutrients on quality and yield, and implications for optimum fertilisation of Chinese waterchestnut are discussed.