Modern high-yielding rice cultivars possibly take up and remove greater quantities of macronutrients than traditional and intermediate cultivars. This study was carried out with the aim of evaluating the extraction and removal of macronutrients by upland rice cultivars. These information are of utmost importance for the correct fertilizer management. The treatments consisted of three upland rice cultivars (Caiapó, a traditional type; BRS Primavera, an intermediate type; and Maravilha, a modern type). Macronutrient accumulation by rice cultivars up to the end of tillering (46 DAE) accounted for only 25 % of the total N and P, and between 35-45 % of the total K, Ca, Mg, and S; after that time, accumulation was intensified. In all of the cultivars, the period of greatest nutrient uptake occurred from 45 to 60 DAE for K, Ca, Mg, and S, and after 65 DAE for N. Phosphorus was taken up at greater rates at 70 DAE by the cultivar BRS Primavera and after 90 DAE by the cultivars Caiapó and Maravilha. The cultivars of the traditional (Caiapó) and intermediate (BRS Primavera) groups took up greater amounts of Ca (143 kg ha ); however, this was lower than the grain yield of cultivar BRS Primavera (6,010 kg ha -1 ). Cultivars with greater yield levels did not necessarily exhibit a greater uptake and removal of nutrients per area, even if they had greater capacity for conversion of the nutrients taken up into the biomass.

-Potassium (K) is an essential nutrient for upland rice growth, but little information on the effects of K on root growth and nutrient uptake capacity of upland rice is found. Therefore, an experiment was conducted under greenhouse conditions to evaluate the influence of soil K levels on root growth and nutrient uptake of four upland rice cultivars. A completely randomized experimental design, in a 4x4 factorial scheme (4 levels of K: 20, 40, 80, and 160 mg dm -3 ; 4 cultivars: Caiapó, BRS-Primavera, IAC-202, and Maravilha) was used, with four replications. Based on regression equations, the highest values of root length density would be found with 136 mg dm -3 of K. The root diameter and dry matter, shoot dry matter and shoot K concentration increased linearly with the increasing K rates. The shoot K concentration of the upland rice cultivars did not differ. The increased level of K in the soil reduced the shoot Ca concentration of intermediate and modern cultivars, and the shoot Mg concentration of all cultivars. The potassium fertilization increased the plant growth, but the magnitude of this effect varied according to the cultivar.

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In no-tillage systems, straw coverage on soil surface is the key to success, and the choice of crops for rotation is crucial to achieve the sustainability and quality that conservation agriculture requires. The objective of this study was to evaluate the agronomic performance of the common bean cultivar IAC Formoso sown in succession to three straw mulch systems (corn alone, corn/Urochloa ruziziensisintercrop and U. ruziziensisalone) and topdress nitrogen rates (0; 40; 80; 120 and 160 kg ha-1N), at the four-leaf stage, three years after the implementation of no-tillage. The experiment was arranged in a randomized block split plot design, with three replications. Common bean highest yields were achieved in succession to U. ruziziensisalone and intercropped with corn. The corn/U. ruziziensisintercrop provided both straw and seed production, allowing for quality no-tillage. Topdressed nitrogen influenced the common bean yield when in succession to corn alone, U. ruziziensisalone and corn/U. ruziziensisintercrop in no-tillage.

The aim of the present study was to evaluate dry matter partitioning and macro-and micronutrient accumulation and distribution in small-sized castor plants grown in season and off-season. The experiments were conducted during the 2005-2006 season and in the 2006 off-season in an Oxisol. A completely randomized block design was used, with eight replications. Plots consisted of plant sampling periods, which were conducted in the vegetative period (17 days after emergence -DAE), the grain fill period (between 73 and 80 DAE) and at end of the cycle (120 DAE). Castor leaves accumulated most of dry matter (DM) and macroand micronutrients in the vegetative period, regardless of the growing period. In the following cycle periods, most of biomass and nutrients were located in the reproductive structures and grains, especially in the offseason crop. It was concluded that leaves and stems are strong nutrient sinks in the castor plant in season crops, while lower water availability during off-season induces plants to use physiological mechanisms to allocate more resources (biomass and nutrients) for their reproduction.Additional keywords: dry matter; macronutrients; micronutrients; Ricinus communis; source/sink relation. ResumoObjetivou-se neste estudo avaliar a partição de matéria seca, o acúmulo e a distribuição de macro e micronutrientes em mamona de porte baixo, cultivada na safra e na safrinha. Os experimentos foram conduzidos na safra de 2005-2006 e na safrinha de 2006, em Latossolo Vermelho distroférrico. Utilizou-se do delineamento em blocos casualizados, com oito repetições. As parcelas foram constituídas pelas épocas de coleta de plantas, que foram realizadas na fase vegetativa (17 dias após a emergência -DAE), na fase de enchimento de grãos (entre 73 e 80 DAE) e no final do ciclo (120 DAE). As folhas da mamoneira, na fase vegetativa, acumularam a maior parte da matéria seca (MS) e dos macros e micronutrientes, independentemente da época de cultivo. Nas fases seguintes do ciclo, a maior proporção de biomassa e nutrientes estava presente nas estruturas reprodutivas e nos grãos, especialmente no cultivo de safrinha. Conclui-se que, no cultivo de safra, as folhas e os caules são fortes drenos de nutrientes na planta de mamona, enquanto na safrinha a menor disponibilidade hídrica faz com que as plantas utilizem mecanismos fisiológicos para alocar mais recursos (biomassa e nutrientes) para sua reprodução.Palavras-chave adicionais: macronutrientes; matéria seca; micronutrientes; relação fonte/dreno; Ricinus communis.