All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. S ugarcane is of major social and economic importance in Brazil. It is one of the most important commodities in Brazilian agribusiness, contributing to the energy and food security of the country, as sugar, ethanol, and biomass for energy are produced from sugarcane (Goldemberg, 2007). Brazilian production of sugarcane has been expanding since the early 2000s, now reaching areas where it has never been planted, mainly driven by the rise in ethanol consumption in the internal market. The coefficient of variation of annual national production was 7.2% from 1990 to 2008, ranging from 5 to 12% among different regions. The new production areas, mainly located in Central and Northeast regions are more often subject to higher risk. Crop simulation models may contribute to improved crop monitoring and yield forecasting, while enhancing our understanding of sugarcane growth and yield. Worldwide, there are several models dedicated to sugarcane crop simulation: AUSCANE (

This study evaluated the effects of climate change on sugarcane yield, water use efficiency, and irrigation needs in southern Brazil, based on downscaled outputs of two general circulation models (PRECIS and CSIRO) and a sugarcane growth model. For three harvest cycles every year, the DSSAT/CANEGRO model was used to simulate the baseline and four future climate scenarios for stalk yield for the 2050s. The model was calibrated for the main cultivar currently grown in Brazil based on five field experiments under several soil and climate conditions. The sensitivity of simulated stalk fresh mass (SFM) to air temperature, CO 2 concentration [CO 2 ] and rainfall was also analyzed. Simulated SFM responses to [CO 2 ], air temperature and rainfall variations were consistent with the literature. There were increases in simulated SFM and water usage efficiency (WUE) for all scenarios. On average, for the current sugarcane area in the State of São Paulo, SFM would increase 24 % and WUE 34 % for rainfed sugarcane. The WUE rise is relevant because of the current concern about water supply in southern Brazil. Considering the current technological improvement rate, projected yields for 2050 ranged from 96 to 129 tha −1 , which are respectively 15 and 59 % higher than the current state average yield.Climatic Change (2013) 117:227-239 DOI 10.1007/s10584-012-0561-

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-A conceptual framework for crop production effi ciency was derived using thermodynamic effi ciency concept, in order to generate a tool for performance evaluation of agricultural systems and to quantify the interference of determining factors on this performance. In Thermodynamics, effi ciency is the ratio between the output and input of energy. To establish this relationship in agricultural systems, it was assumed that the input energy is represented by the attainable crop yield, as predicted through simulation models based on environmental variables. The method of FAO's agroecological zones was applied to the assessment of the attainable sugarcane yield, while Instituto Brasileiro de Geografi a e Estatística (IBGE) data were used as observed yield. Sugarcane effi ciency production in São Paulo state was evaluated in two growing seasons, and its correlation with some physical factors that regulate production was calculated. A strong relationship was identifi ed between crop production effi ciency and soil aptitude. This allowed inferring the effect of agribusiness factors on crop production effi ciency. The relationships between production effi ciency and climatic variables were also quantifi ed and indicated that solar radiation, annual rainfall, water defi ciency, and maximum air temperature are the main factors affecting the sugarcane production effi ciency.Index terms: Saccharum, pedological aptitude, geoprocessing, agrometeorological modeling. Efi ciência da produção de cana-de-açúcar em duas safras no Estado de São PauloResumo -Um conceito de efi ciência de produção agrícola foi derivado da Termodinâmica, para gerar um indicador para avaliação do desempenho de sistemas de produção agrícola e quantifi cação da interferência dos fatores determinantes desse desempenho. Em Termodinâmica, a efi ciência de um processo é dada pela razão entre a energia recuperada e a energia utilizada. Para estabelecer essa relação em sistemas agrícolas, admitiu-se que a energia utilizada seja dada pela produtividade atingível, estimada por modelos de simulação desenvolvidos com base em variáveis ambientais. O método das zonas agroecológicas da FAO foi utilizado para a estimativa da produtividade atingível, e os dados do Instituto Brasileiro de Geografi a e Estatística (IBGE), como produtividade observada. Avaliou-se a efi ciência da produção de cana-de-açúcar no Estado de São Paulo, em duas safras, e calculou-se sua correlação com alguns fatores do meio físico que regulam a produção. Foi identifi cada forte relação da efi ciência da produção agrícola com a aptidão agrícola do solo. Isto permitiu inferir sobre o efeito de fatores relativos ao agronegócio sobre a efi ciência da produção agrícola. Foi possível identifi car, ainda, que a radiação solar, a defi ciência hídrica, a quantidade de chuva e a temperatura máxima são as principais variáveis climáticas que afetam a efi ciência da produção agrícola.Termos para indexação: Saccharum, aptidão pedológica, geoprocessamento, modelagem agrometeorológica.