INTRODUÇÃOA cana-de-açúcar, por tratar-se de uma cultura semiperene, pode ficar no campo por vários anos (média de quatro a sete anos, em áreas de produção de usinas), sem, muitas vezes, a devida correção de acidez do solo e/ou manutenção de adubação adequada, a cada safra, que, normalmente, são realizadas de modo mais criterioso, quando ocorre reforma do canavial. Este fato não anula a necessidade de manutenção de sua fertilidade, pois, com o passar dos anos, os valores de pH vão diminuindo, levando à redução da saturação por bases do solo e aumento dos teores de Al trocável (Rossetto et al. 2008). ABSTRACT RESUMONo sistema de colheita mecanizada, grande quantidade de palha é depositada no solo, tornando--se reserva de nutrientes, devido à decomposição da sua matéria orgânica (Oliveira et al. 1999 Unburned ratoon sugarcane yield according to gypsum and vinasse dosesUnderstanding the influence of sugarcane straw over the application dynamic of vinasse and correctives is essential for an effective management of the production system. This study aimed at evaluating soil fertility, stalk yield and technological quality of ratoon sugarcane (2nd cycle), according to vinasse and gypsum application, in an Oxisol, in the Northwest São Paulo State, Brazil. The study was carried out with the RB867515 cultivar and the experimental design was randomized blocks with four replications, in a 2x3 factorial scheme, i.e., with and without gypsum (1.0 t ha

Panicum maximum Jacq. 'Mombaça' (Guinea grass) is a C 4 forage grass widely used in tropical pastures for cattle feeding. In this study, we evaluated the isolated and combined effects of warming and elevated CO 2 concentration [CO 2 ] during summer on nutrient content, nutrient accumulation, nutrient use efficiency and growth of P. maximum under field conditions. Field temperature and [CO 2 ] were controlled by temperature free-air controlled enhancement and free-air CO 2 enrichment systems, respectively. We tested two levels of canopy temperature: ambient temperature (aT) and 2˚C above ambient temperature (eT), as well as two levels of atmospheric [CO 2 ]: ambient [CO 2 ] (aCO 2) and 200 ppm above ambient CO 2 (eCO 2). The experiment was established in a completely randomized design with four replications, in a 2×2 factorial scheme. After pasture establishment, plants were exposed to the treatments during 30 days, with evaluations at 9, 16, 23 and 30 days after the treatments started. Results were dependent on the time of the evaluation, but in the last evaluation (beginning of the grazing), contents of N, K, Mg and S did not change as a function of treatments. However, P decreased as a function of warming under both levels of [CO 2 ], and Ca increased under [eCO 2 ] combined with warming. There was an increase in root dry mass under warming treatment. Combined treatment increased N, Ca and S accumulation without a corresponding increase in the use efficiency of these same nutrients, indicating that the fertiliser dose should increase in the next decades due to climate change. Our short-term results in young and well fertilized pasture suggest that under the combination of [eCO 2 ] and eT conditions, P. maximum productivity will increase and the nutritional requirement for N, Ca and S will also increase.

Stylosanthes capitata Vogel is a C3 forage legume widely cultivated in tropical and subtropical pastures. However, the nutrient dynamics of this species under future climate change is unknown. Therefore, this study aimed to evaluate the nutrient content, nutrient accumulation, nutrient use efficiency and growth of S. capitata exposed to increased [CO2] and temperature under field conditions using two levels of atmospheric [CO2] (ambient and elevated—600 ppm) and two canopy temperature (ambient and elevated—2°C). Treatments were applied at field conditions, for 30 days, using a free‐air carbon dioxide enrichment (FACE) and a free‐air temperature‐controlled enhancement (T‐FACE) systems. Warming showed no effects on macronutrient content, but increased the accumulation of nitrogen, potassium, calcium, magnesium and sulphur, the nutrient use efficiency and root dry mass. Elevated [CO2] alone had no effect on most of the parameters evaluated. However, the combination of elevated [CO2] with warming improved the nutrient accumulation, nutrient use efficiency and whole‐plant growth more than under isolated conditions of elevated [CO2] or warming. Based on our short‐term results, we concluded that an increment of atmospheric [CO2] and temperature will benefit S. capitata growth, suggesting no alterations in the actual fertilizer programs for this species.

14Panicum maximum Jacq. 'Mombaça' (guinea grass) is a C 4 forage grass widely used in 15 tropical pastures for cattle feeding. In this study, we evaluated the isolated and combined 16 effects of warming and elevated CO 2 concentration [CO 2 ] during summer on the nutrient 17 content, nutrient accumulation, nutrient use efficiency and growth of P. maximum under 18 field conditions with adequate water supply. The temperature and [CO 2 ] in the field were 19 controlled by temperature free-air controlled enhancement and free-air CO 2 enrichment 20 systems, respectively. We tested two levels of canopy temperature: ambient temperature 21 and 2°C above ambient temperature, as well as two levels of atmospheric [CO 2 ]: ambient 22 [CO 2 ] (aCO 2 ) and 200 ppm above ambient CO 2 (eCO 2 ). The experiment was established 23 in a completely randomised design with four replications, in a 2×2 factorial scheme. After 24 the pasture establishment, plants were exposed to the treatments for 30 days, with 25 evaluations at 9, 16, 23 and 30 days after the treatments started. Results were dependent 26 on the time of the evaluation, but in the last evaluation (beginning of the grazing), contents 27 of N, K, Mg and S did not change as a function of treatments, P decreased as a function 28 of warming, in [aCO 2 ] and [eCO 2 ], and Ca increased under [eCO 2 ] combined with 29 warming. There was an increase in root dry mass under warming treatment. Combined 30 treatment increased N, Ca and S accumulation without a corresponding increase in the 31 use efficiency of these same nutrients, indicating that the fertiliser dose should increase 32 in the next decades due to human-induced climate change. Our short-term results suggest 33 that the combination of high [CO 2 ] and temperature will increase P. maximum 34 productivity and that the nutritional requirement for N, Ca and S will increase. 35 36 38During the last decades, anthropic emissions of greenhouse gases, such as carbon dioxide 39 (CO 2 ), nitrous oxide (N 2 O) and methane (CH 4 ), have induced alterations in the natural 40 climate cycles of the Earth, elevating the mean surface temperature of the planet [1,2]. 41 The global temperature has been increasing in the last years, and several climate models 42 estimate that this trend will continue in the next decades [3]. Many climate change 43 scenarios have been proposed, depending on the future emissions of greenhouse gases 44 and mitigation policies. According to a moderate-impact scenario outlined by the 45 Intergovernmental Panel on Climate Change (IPCC), the atmospheric CO 2 concentration 46 ([CO 2 ]) will reach 600 ppm by 2100, while the global surface temperature will be between 47 2.0 and 3.7°C above the pre-industrial average temperature [3]. 48In tropical and sub-tropical regions, livestock is one of the most important 49 economic activities, and pastures cover extensive areas of the territory, being the main 50 source for cattle feeding in most of these regions [4]. The effects of climate change on 51 the nutritional ...