Best management practice of potassium for sunflower (Helianthus annuus, L.) in Northwest China

This northwestern China study on 4R K management for sunflower examined K application, the effect of K source and timing, and the interactions between water regimes and KCl rates on sunflower yield and quality.

In Gansu, K fertilization increased the seed yield of oil sunflower by an average of 11%, and 14 of 20 sites showed a positive yield response, and increased head diameter, 1000-seed weight, kernel weight, oil content, unsaturated fatty acid, oleic acid, linoleic acid, linolenic acid. Potassium also increased edible sunflower seed yield in Inner Mongolia (IMAR) by 7%, where 19 of 20 sites showed a positive yield response, and increased kernel weight, kernel rate and oil content, saturated, unsaturated fatty acid and minerals. The average agronomic efficiency of K was 4.0 kg seed/kg K₂O for oil sunflower in Gansu, and 3.2 kg seed/kg K₂O for edible sunflower in IMAR. An average of 4.7 kg N, 2.8 kg P₂O₅ and 16.0 kg K₂O was required for producing 100 kg oil sunflower seeds, and a mean of 3.3 kg N, 1.7 kg P₂O₅ and 10.8 kg K₂O was required for producing 100 kg edible sunflower seeds.

For oil sunflower in Gansu, no significant differences existed between K sources for seed yield, total K uptake, disk diameter, 1000-seed weight, and kernel rate. Basal application of K fertilizer resulted in more plant K accumulation and higher 1000-seed weight than split applications. For edible sunflower in IMAR, source and timing of K application did not significantly influence seed yield and its components except that the potassium sulfate source resulted in more kernel weight than KCl. Source and timing of K application did not affect oil content and its components, amino acid and fiber contents for both oil and edible sunflower.

For oil sunflower in Gansu, rainfed plastic mulched systems were superior to rainfed and/or flooding irrigation without mulch in seed yield, 1000-seed weight, kernel rate, total uptake K, agronomic efficiency, oil content, and fatty acid components. 1000-seed weight, kernel weight, total Cl^- uptake, oil content, unsaturated fatty acid, oleic acid increased with the increased KCl rate. The treatment of rainfed with plastic mulch applied KCl at 120 kg K₂O/ha was the best practice. For edible sunflower in IMAR, seed yield, disk diameter, 1000-seed weight was in the sequence of drip irrigation > rainfed plastic mulched practices ≥ rainfed without mulch. Drip irrigation resulted in more K and Cl^- accumulation than rainfed or rainfed with plastic mulch, and increased with KCl rate. Seed yield and yield components increased with increase of KCl application rate. Good soil moisture conditions did not affect oil content and the components of oil fatty acid.