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.

Proxy reconstruction of ultraviolet-B irradiance at the Earth’s surface, and its relationship with solar activity and ozone thickness

Solar ultraviolet-B (UV-B) irradiance that reaches the Earth’s surface acts as a biotic stressor and has the potential to modify ecological and environmental functioning. The challenges of reconstructing ultraviolent (UV) irradiance prior to the satellite era mean that there is uncertainty over long-term surface UV-B patterns, especially in relation to variations in solar activity over centennial and millennial timescales. Here, we reconstruct surface UV-B irradiance over the last 650 years using a novel UV-B proxy based on the chemical signature of pollen grains. We demonstrate a statistically significant positive relationship between the abundance of UV-B absorbing compounds in Pinus pollen and modelled solar UV-B irradiance. These results show that trends in surface UV-B follow the overall solar activity pattern over centennial timescales, and that variations in solar output are the dominant control on surface level UV-B flux, rather than solar modulated changes in ozone thickness. The Pinus biochemical response demonstrated here confirms the potential for solar activity driven surface UV-B variations to impact upon terrestrial biotas and environments over long timescales.

When environmental factors become stressors: interactive effects of vermetid gastropods and sedimentation on corals

Environmental stressors often interact, but most studies of multiple stressors have focused on combinations of abiotic stressors. Here we examined the potential interaction between a biotic stressor, the vermetid snail Ceraesignum maximum , and an abiotic stressor, high sedimentation, on the growth of reef-building corals. In a field experiment, we subjected juvenile massive Porites corals to four treatments: (i) neither stressor, (ii) sedimentation, (iii) vermetids or (iv) both stressors. Unexpectedly, we found no effect of either stressor in isolation, but a significant decrease in coral growth in the presence of both stressors. Additionally, seven times more sediment remained on corals in the presence (versus absence) of vermetids, likely owing to adhesion of sediments to corals via vermetid mucus. Thus, vermetid snails and high sedimentation can interact to drive deleterious effects on reef-building corals. More generally, our study illustrates that environmental factors can combine to have negative interactive effects even when individual effects are not detectable. Such ‘ecological surprises' may be easily overlooked, leading to environmental degradation that cannot be anticipated through the study of isolated factors.