Growth and nutrient absorption in chufa (Cyperus esculentus L. var. sativus Boeck.) in soilless culture

The efficiency of fertilisation in agriculture is often low and, provided one knows the nutrient uptake rate, the efficiency can be improved by synchronising nutrient supply with nutrient demand. Growth, the time-course of nutrient accumulation and its partitioning between different organs in chufa (Cyperus esculentus L. var. sativus Boeck.), an under-exploited cultivated plant, were examined. The study was conducted in soilless, open-field conditions, at a planting density equivalent to 55,500 plants ha(-1) in three consecutive seasons. Plants were sampled, fractionated into leaves, roots, and tubers, then dried and weighed. Their macronutrient contents were analysed each fortnight. On average, the yield was 5.0 kg fresh weight of tuber m(-2). Growth of whole plants, until 90 d after planting, obeyed an exponential function of time. The relative growth rate (RGR) for this period was therefore determined. The highest N and K concentrations were recorded in leaves, and the highest P, Ca, and Mg concentrations were found in roots. The highest accumulations of N and P were found in tubers, and of K and Ca in leaves. Nitrogen had the highest nutrient accumulation (58.3 g m(-2)) as well as the highest specific uptake rate.