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Crop multi-model ensembles (MME) have proven to be effective in increasing the accuracy of simulations in modelling experiments. However, the ability of MME to capture crop responses to changes in sowing dates and densities has not yet been investigated. These management interventions are some of the main levers for adapting cropping systems to climate change. Here, we explore the performance of a MME of 29 wheat crop models to predict the effect of changing sowing dates and rates on yield and yield components, on two sites located in a high-yielding environment in New Zealand. The experiment was conducted for 6 years and provided 50 combinations of sowing date, sowing density and growing season. We show that the MME simulates seasonal growth of wheat well under standard sowing conditions, but fails under early sowing and high sowing rates. The comparison between observed and simulated in-season fraction of intercepted photosynthetically active radiation (FIPAR) for early sown wheat shows that the MME does not capture the decrease of crop above ground biomass during winter months due to senescence. Models need to better account for tiller competition for light, nutrients, and water during vegetative growth, and early tiller senescence and tiller mortality, which are exacerbated by early sowing, high sowing densities, and warmer winter temperatures., This study was a part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Wheat Phase 4 and was supported by the French National Research Institute for Agriculture, Food (INRAE) and the International Maize and Wheat Improvement Center (CIMMYT) through the International Wheat Yield Partnership (IWYP, grant IWYP115). SD and PM acknowledge support from the metaprogram Agriculture and forestry in the face of climate change: adaptation and mitigation (CLIMAE) of INRAE. YC and FT acknowledge support from the National Natural Science Foundation of China (No. 31761143006). RPR and GBM acknowledge financial support from BARISTA project (031B0811A) through ERA-NET SusCrop under EU-FACCE JPI. KCK was funded by the German Federal Ministry of Education and Research (BMBF) through the BonaRes project ’’I4S’’ (031B0513I). AS and TG acknowledge funding by the German Federal Ministry of Education and Research (BMBF) through the BonaRes Project “Soil3” (FKZ 031B0026A). KCK and JEO were supported by the Ministry of Education, Youth and Sports of Czech Republic through SustES—Adaption strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/000797). FE acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC 2070 – 390732324”. TKDW was funded by the German Research Foundation (DFG, Grant Agreement SFB 1253/1 2017). MAS and NS at Rothamsted Research received grant-aided support from the Biotechnology and Biological Sciences Research Council (BBSRC) through Designing Future Wheat [BB/P016855/1] and Achieving Sustainable Agricultural Systems [NE/N018125/1] jointly funded with NERC. TP and FT are supported by the DivCSA project funded by the Academy of Finland (decision no. 316215).

FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais O estudo da dinâmica do perfilhamento na primavera permite conhecer os mecanismos pelos quais a gramínea forrageira retoma a sua rebrotação, após as condições de clima adversas vigentes no inverno. O objetivo com este trabalho foi determinar o efeito da altura e da roçada do pasto previamente diferido sobre o perfilhamento da Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu (capim-marandu) durante a primavera e o inicio do verão. Quatro condições do pasto ao término do inverno foram avaliadas: baixo (15,1 cm e 4.600 kg/ha de MS), médio (23,2 cm e 5.940 kg/ha de MS), alto (31,4 cm e 7.640 kg/ha de MS) e alto/roçado (31,3 cm e 7.200 kg/ha de MS, porém roçado para 8 cm). O delineamento foi inteiramente casualizado, com três repetições. Em outubro, os pastos baixo e alto/roçado tiveram taxa de aparecimento de perfilho (TApP) e índice de estabilidade de perfilhos (IE) superiores aos pastos médio e alto. Nos demais meses, a TApP e o IE foram iguais para todas as condições de pastos. O IE foi muito alto em outubro, reduziu em novembro e dezembro e voltou a aumentar em janeiro. Em outubro, a taxa de mortalidade de perfilho (TMoP) foi menor no pasto baixo, intermediária naqueles médio e alto, e maior no pasto alto/roçado Em janeiro de 2014, o percentual de perfilho jovem foi maior nos pastos médio e alto, em relação aos baixo e alto/roçado, contrariamente ao observado para a percentagem de perfilho maduro. Em janeiro de 2014, a percentual de perfilho velho foi maior no pasto alto, intermediário nos pastos baixo e médio e menor no pasto alto/roçado. O pasto de capim-marandu diferido e mais baixo ao término do inverno apresenta maior perfilhamento e estabilidade da população de perfilhos na primavera, em comparação aos pastos altos. A roçada do capim-marandu alto no fim do inverno não compromete a estabilidade da população de perfilhos no pasto na primavera. The study of the dynamics of tillering on spring allows to know the mechanisms by which the forage plant resumes its regrowth, after the adverse weather conditions prevailing in winter. The objective of this work was to determine the effect of the height and mowed of the previously deferred pasture about the tillering of Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu (capim-marandu) during the spring and the early the summer. Four pasture conditions at the end of winter was evaluited: short (15,1 cm e 4.600 kg/ha de DM), medium (23,2 cm e 5.940 kg/ha de DM), tall (31,4 cm e 7.640 kg/ha de DM) and tall/mowed (31,3 cm e 7.200 kg/ha de DM, however mowed to 8.0 cm). A completely was randomized design, and with three replications. In October, low and high/mowed pastures had tiller appearance rate (TApR) and stability index of the tiller population (SI) greater that medium and tall pastures. In the remaining months, TApR and SI were the same for all pasture conditions. SI was very high in October, declined in November and December and increased again in January. In October, the tiller mortality rate (TMoR) was lower in the low pastures, intermediate in the medium and high pastures, and greater in the high/mowed pastures. The percentage of young tillers was greater in the medium and tall pastures, in relation to the short and tall/mowed, a pattern of response contrary to that observed for the percentage of mature tillers. The percentage of old tillers was greater in the tall pastures, intermediate in the short and medium pastures, and lower in the tall/mowed pastures. Deferred and shorter marandu palisadegrass pastures at the end of winter showed greater stability of the tiller population and tillering in early spring compared to tall pastures. The mowing of marandu palisadegrass at the end of winter does not compromise the stability of the tiller population from spring. Dissertação (Mestrado)