Foliar Application of Liquid-Silicate Rock Fertilizer Reduced Pest and Disease Attacks and Improved Bean Production of Cocoa

Besides the lack of soil fertilization, the primary biotic stressor limiting the production of cocoa (Theobroma cacao L.) in Indonesia is pest and disease attacks (PDAs). As a part of the efforts to find out the appropriate solution for the farming constraints, a field trial was carried out for 14 months (2015 – 2016) in Genggelang - North Lombok Regency, Indonesia. The main objective of the experiment was to identify the effects of the use of locally-available materials, i.e., liquid-silicate rock fertilizer (LSRF), botanical pesticide (BP) of neem, and black ants (BA) of Doliccoderus thoracic, on PDAs, bean production, and polyphenol and lignin contents of cocoa pod shell. A randomized complete block design was laid out in three blocks, and the treatments were LSRF, LSRF+BP, LSRF+BA, BA, and control. Results reveal that the application of those materials reduced the intensity of pest and disease attacks (e.i., respectively, 6 - 24 % and 3 - 9 % lower than for that of the control), increased 18 – 119 % of bean production, and improved the polyphenol and lignin contents of pod shell. The highest increase (119 %) of bean production was due to the foliar application of LSRF. The positive effect of the treatments, especially the use of LSRF, associated with the improvement of the resistance of cocoa to PDAs and appropriate supply of plant-essential nutrients. Therefore, the foliar application of LSRF may be promoted as a proper method to improve the production of cocoa, especially of that grown on less fertile soils.