Effects of K application on the K, Ca and Mg concentration of cocoa leaves and soil and its effects on plant growth

English. The above mentioned experiment was conducted in the laboratory and greenhouse of Indonesian Oil Palm Research Institute at Medan. This experiment used typic paleudult soil, taken from cocoa area of Bukit Sentang estate. The status of exchangeable content was low, Ca 0.15 me K/100 g and its value was equal to 2 percent of K saturation level. The result showed that K application increased significantly cocoa growth and dry matter production. The optimum K application was 150 ppm K2O and the resulted K: Ca: Mg ratio was 8:69:23, which was favorable for optimum K and Ca availability in soil. Application of 200 ppm K2O decreased cocoa growth and dry matter production. Critical level exchangeable K was 0,375 me K/100 g and this value was equal to 5 percent of K saturation level. Application of K also increased significantly the concentration of K in soil and cocoa leaves. On the other hand, this K treatment also decreased Ca and Mg content in soil and cocoa leaves

unknown. Penelitian pengaruh pemberian K terhadap pertumbuhan kakao dan pengaruhnya terhdap kadar K, C, dan Mg di dalam tanah dan daun ini dilakukan di laboratorium dan rumah kaca Pusat Penelitian Kelapa Sawit Medan. Contoh tanah yang digunakan tergolong Typic paleudult yang diambil dari areal kakao kebun Bukit Sentang yang mempunyai status hara K rendah, dengan kadar K tertukarkan 0,15 me K/100 g atau tingkat kejenuhan K sebesar 2 persen. Hasil penelitian menunjukkan bahwa pemberian K yang optimum sebesar 150 ppm K2O dan nisbah K/Ca/Mg pada perlakuan ini sebesar 8/69/23. Pemberian K pada taraf 200 ppm K2O sudah berpengaruh negatif terhadap pertumbuhan kakao. Titik kritis K tertukarkan dicapai pada nilai 0,375 me K/100 g pada tingkat kejenuhan K sebesar 5 persen. Pemberian K pada taraf yang dicobakan juga berpengaruh nyata terhadap peningkatan kadar K di dalam tanah dan daun kakao. Namun, perlakuan K ini berpengaruh terhadap penurunan kadar Ca dan Mg di dalam tanah dan daun