Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litter and methodologies, adding major uncertainty to syntheses, comparisons and meta-analyses across different experiments and sites. In the TeaComposition initiative, the potential litter decomposition is investigated by using standardized substrates (Rooibos and Green tea) for comparison of litter mass loss at 336 sites (ranging from -9 to +26 °C MAT and from 60 to 3113 mm MAP) across different ecosystems. In this study we tested the effect of climate (temperature and moisture), litter type and land-use on early stage decomposition (3 months) across nine biomes. We show that litter quality was the predominant controlling factor in early stage litter decomposition, which explained about 65% of the variability in litter decomposition at a global scale. The effect of climate, on the other hand, was not litter specific and explained <0.5% of the variation for Green tea and 5% for Rooibos tea, and was of significance only under unfavorable decomposition conditions (i.e. xeric versus mesic environments). When the data were aggregated at the biome scale, climate played a significant role on decomposition of both litter types (explaining 64% of the variation for Green tea and 72% for Rooibos tea). No significant effect of land-use on early stage litter decomposition was noted within the temperate biome. Our results indicate that multiple drivers are affecting early stage litter mass loss with litter quality being dominant. In order to be able to quantify the relative importance of the different drivers over time, long-term studies combined with experimental trials are needed.

Quinoa (Chenopodium quinoa Willd.) quickly adapts to different climatic conditions; however, low soil fertility conditions and inadequate soil water levels may reduce yield. The objective of this study was to evaluate the effect of irrigation levels and potassium fertilization for quinoa production in the Cerrado Oxisol. The experiment was performed in a greenhouse, located at the Federal University of Mato Grosso (UFMT), Campus of Rondonópolis -Brazil, using soil collected from a Cerrado Oxisol. The experimental design was a randomized complete block design in a 5x5 factorial scheme with four replicates, corresponding to five potassium doses (0, 100, 200, 400 and 600 mg dm -3 ) and five irrigation levels (50, 75, 100, 125 and 150% of field capacity). The variables of dry mass of shoot, dry mass of roots, water use efficiency, mass of 100 grains, production and number of grains were analyzed. The dry mass of the aerial part and the roots are influenced by the potassium fertilization in the doses between 530 and 600 mg dm -3 . All the vegetative and productive characteristics were affected by the treatments. The highest water use efficiency was observed at the potassium (K 2 O) dose of 375 mg dm -3 and a 50% irrigation level.

No abstract

The chief limiting factor in sunflower (Helianthus annuus L.) development is water deficit. Besides the dearth of water, large amounts of mainly potassium (K) are essential for the favourable development and bountiful harvest of the culture. This study aimed to evaluate the growth of sunflower plants cv. SYN 042 cultivated in red Cerrado Oxisol with controlled irrigation levels and K doses. Randomized block design was selected in a 5x4 factorial scheme, administering 5 K doses (0, 40, 80, 160 and 240 mg dm -3 of K 2 O) and 4 different water replacement levels in the soil (75, 100, 125 and 150% of field capacity (FC)), with 4 replications. The following characteristics were evaluated: Plant height, stem diameter, Chlorophyll index, inner and outer diameters of the chapter,

No abstract