Organic residue with high potassium content on sunflower cultivars

The use of organic sources that include levels of potassium, in addition to having an influence on the achenes and on plant development, reduces production costs and has less impact on the environment. The aim of this study was to evaluate the efficiency of fertilisation using organic residue generated by the coffee roasting process, which has a high level of potassium, on agronomic characteristics, production components and physiological quality of the achenes. The experimental design was a 2x4+2 factorial scheme, with two cultivars, four doses of organic residue  (T1=0, T2=40, T3=80 and T4=120 kg K ha-1), plus a control of potassium chloride at a dose of 60 kg K ha-1 for each cultivar. The variables under analysis were plant height, stem diameter at ground level, capitulum diameter, number of leaves, leaf area, leaf area index, 1000-achene weight, productivity and oil content. The physiological quality of the achenes was also determined by the germination test, first germination count, seedling emergence, emergence speed index, shoot length, shoot dry weight and accelerated-ageing test. Fertilisation with organic residue is efficient for the agronomic characteristics and production components of the sunflower; doses of less than 40 kg K ha-1 or over 70 kg K ha-1 from the organic residue may have a negative effect on the physiological quality of sunflower achenes.