A determinação das quantidades de nutrientes absorvidas durante o ciclo de desenvolvimento é de suma importância para estabelecer as épocas em que esses elementos são mais exigidos e as quantidades corretas que devem ser disponibilizadas à cultura da batata. No entanto, quase não existem essas informações para as principais cultivares utilizadas no Brasil. O objetivo deste trabalho foi avaliar a extração e a exportação de macronutrientes pelas cultivares de batata Ágata, Asterix, Atlantic, Markies e Mondial. O experimento foi conduzido durante a safra de inverno, em um Latossolo Vermelho, no município de Itaí (SP). As parcelas foram constituídas pelas cinco cultivares, e as subparcelas, por épocas de coletas, realizadas no momento do plantio e a cada sete dias após a emergência. As cultivares Mondial e Asterix, mais produtivas, apresentaram maior extração de macronutrientes, com quantidades médias por hectare de 116 kg de N, 18 kg de P, 243 kg de K, 50 kg de Ca e 13 kg de Mg, enquanto as cultivares Ágata, Atlantic e Markies extraíram menor quantidade, com valores médios de 92, 14, 178, 35 e 9 kg ha-1, respectivamente. A maior demanda por macronutrientes pelas cultivares estudadas ocorreu na fase inicial de enchimento dos tubérculos (42 a 70 DAP). A exportação de macronutrientes não esteve diretamente relacionada com a produtividade de tubérculos, já que a cultivar mais produtiva (Mondial) não foi a que exportou a maior quantidade de macronutrientes. A cultivar Asterix exportou maior quantidade de N, P, K e Mg, com valores de 88, 15, 220 e 8 kg ha-1, respectivamente, enquanto a menor exportação foi observada na cultivar Atlantic, com 48 kg ha-1 de N, 10 kg ha-1 de P, 143 kg ha-1 de K e 5 kg ha-1 de Mg. A variação entre as cultivares na extração, especialmente de K e N, indica necessidade de manejo diferencial da adubação.

Silicon has beneficial effects on many crops, mainly under biotic and abiotic stresses. Silicon can affect biochemical, physiological, and photosynthetic processes and, consequently, alleviates drought stress. However, the effects of Si on potato (Solanum tuberosum L.) plants under drought stress are still unknown. The objective of this study was to evaluate the effect of Si supply on some biochemical characteristics and yield of potato tubers, either exposed or not exposed to drought stress. The experiment was conducted in pots containing 50 dm3 of a Typic Acrortox soil (33% clay, 4% silt, and 63% sand). The treatments consisted of the absence or presence of Si application (0 and 284.4 mg dm−3), through soil amelioration with dolomitic lime and Ca and Mg silicate, and in the absence or presence of water deficit (−0.020 MPa and −0.050 MPa soil water potential, respectively), with eight replications. Silicon application and water deficit resulted in the greatest Si concentration in potato leaves. Proline concentrations increased under lower water availability and higher Si availability in the soil, which indicates that Si may be associated with plant osmotic adjustment. Water deficit and Si application decreased total sugars and soluble proteins concentrations in the leaves. Silicon application reduced stalk lodging and increased mean tuber weight and, consequently, tuber yield, especially in the absence of water stress.

Resumo -O objetivo deste trabalho foi avaliar o crescimento, o acúmulo e a distribuição de matéria seca (MS) nas cultivares de batata (Solanum tuberosum) Ágata, Asterix, Atlantic, Markies e Mondial, durante a safra de inverno. O experimento foi conduzido de junho a outubro de 2008, no munícipio de Itaí, SP. Utilizou-se o delineamento experimental de blocos ao acaso, em parcelas subdivididas, com quatro repetições. As parcelas foram constituídas pelas cultivares, e as subparcelas por épocas de coletas de plantas para avaliação: no plantio e a cada sete dias após a emergência. Todas as cultivares têm crescimento lento até o início da fase de enchimento de tubérculos. Porém, as cultivares Asterix, Atlantic e Markies são mais precoces do que a Mondial no estabelecimento de taxas máximas de acúmulo de matéria seca. As cultivares Asterix e Mondial apresentam maior número de folhas por planta, produtividade de tubérculos, taxa de acúmulo e produção de MS, mas a cultivar Mondial é menos eficiente na alocação de MS nos tubérculos que as demais cultivares. As cultivares com maior taxa máxima de acúmulo produzem maior quantidade de MS, mesmo apresentando menor período de duração da taxa máxima de acúmulo.Termos para indexação: Solanum tuberosum, análise de crescimento, partição de matéria seca, taxa de crescimento. Growth and dry matter accumulation and distribution in potato cultivars during the winter crop seasonAbstract -The objective of this work was to evaluate growth and dry matter accumulation and distribution of potato cultivars (Solanum tuberosum) Ágata, Asterix, Atlantic, Markies, and Mondial, during the winter crop season. The experiment was carried out in Itaí, São Paulo state, Brazil, from June to October 2008. A randomized complete block design with split-plots and four replications was used. Plots comprised the potato cultivars and subplots were established by plant sampling times: at planting and every seven days after emergence. All the cultivars show slow growth until the onset of the tuber bulking stage. However, Asterix, Atlantic and Markies are earlier than Mondial in obtaining the maximum rates of dry matter accumulation. The Asterix and Mondial cultivars have more leaves per plant, higher tuber yield, higher maximum accumulation rates and dry matter production, but Mondial is less efficient in dry matter alocation to the tubers than the other cultivars. The cultivars with higher maximum accumulation rates provided higher amounts of dry matter, even with shorter terms of the maximum accumulation rate.

In tropical regions with dry winters, low plant biomass accumulation during the period between spring–summer crop cultivations can negatively impact soil resources and make the no‐till (NT) system unsustainable. Incorporating palisadegrass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster] [syn. Brachiaria brizantha (Hochst. Ex A. Rich) Stapf] in traditional grain production areas could improve soil quality for subsequent crops and lead to positive effects on grain yield. The objective of this study was to evaluate the effects of growing palisadegrass on soil fertility, plant nutrition, and grain yield of subsequent cash crops in a tropical region. The experiment was performed in southeastern Brazil in plots that were grown for two consecutive growing seasons (2002–2003 and 2003–2004) with either monocropped corn (Zea mays L.) or corn intercropped with palisadegrass. An initial evaluation of soil fertility was performed in November 2004 when the land was either fallow (following monocropped corn) or covered by palisadegrass (intercropped areas). After the preceding treatments, the following crops were cultivated: soybean [Glycine max (L.) Merr.] during the 2004–2005 and 2005–2006 spring–summer, white oat (Avena sativa L.) during the 2005 and 2006 fall–winter, and corn during the 2006–2007 spring–summer. Intercropping palisadegrass with corn increased the soil fertility compared to monocropped corn. Soybean, white oat, and corn all had higher leaf macronutrient concentrations and grain yields in previously intercropped areas than in monocropped areas. Therefore, the periodic, short‐term incorporation of a perennial forage grass, such as palisadegrass, as a cover crop is recommended to increase grain production and to improve the soil fertility of grain‐production areas.

Silicon can alleviate biotic and abiotic stresses in several crops, and it has beneficial effects on plants under nonstressed conditions. However, there is still doubt about foliar‐applied Si efficiency and Si effects on mineral nutrition, physiological processes, and growth of potato (Solanum tuberosum L.) plants under well‐watered conditions. The objective of this study was to evaluate the effect of soil and foliar application of soluble Si on Si accumulation, nutrients, and pigments concentration as well as gas exchange and growth of potato plants. The experiment was conducted under greenhouse conditions in pots containing 35 dm3 of a Typic Acrortox soil. The treatments consisted of a control (no Si application), soil application of soluble Si (50 mg dm−3 Si), and foliar application of soluble Si (three sprays of 1.425 mM Si water solution, prepared with a soluble concentrate stabilized silicic acid), with eight replications. Both soil and foliar application of Si resulted in higher Si accumulation in the whole plant. Foliar application of Si resulted in the greatest Si concentration in leaves, and soil application increased Si concentration in leaves, stems, and roots. Silicon application, regardless of the application method, increased leaf area, specific leaf area, and pigment concentration (chlorophyll a and carotenoids) as well as photosynthesis and transpiration rates of well‐watered potato plants. However, only soil application increased P concentration in leaves and dry weight of leaves and stems.

The development of technologies that provide rapid acidity amelioration of the soil profile through the surface application of amendments and phosphogypsum, such as no-till (NT) systems, is extremely important to provide adequate chemical conditions in tropical soils with low natural fertility, which limits the grain yield of upland rice (Oryza sativa L.). Thus, this study aimed to evaluate the effects of surface applications of lime, silicate, and phosphogypsum, applied individually or in mixtures, on the chemical properties of the soil profile in an NT system and to determine their effects on the nutrition, yield components, and grain yield of upland rice. The experiment was designed as a completely randomized block with eight treatments replicated four times. The combination of phosphogypsum with lime and/or silicate improved the surface and subsurface soil chemical properties 12 months following application. The mixtures increased the concentrations of K, Ca, Mg, N-NO 3 − , and S-SO 4 2− in the subsurface layers. The sulphur concentration in the flag leaves of upland rice was higher with phosphogypsum application. The number of panicles per m 2 and grain yield of upland rice were positively influenced by the surface application of soil acidity amendments and phosphogypsum mixtures.

Core Ideas Urochloa brizantha as cover crop produced more biomass and nutrient cycling than U. ruziziensis. Nitrogen fertilizer on Urochloa cover crops increased biomass production but limited maize yield. The highest maize yields were obtained when N was applied on day before seeding or under conventional method (N applied at seeding plus sidedressing). All N applied on Urochloa residue prior to maize can be an option, but is risky in regions of high rainfall. Crop residue decomposition is slower in no‐till (NT) systems, especially in high‐biomass systems. Adopting optimum nN management can provide increased soil coverage and synchronize the supply of nutrients with the period of highest crop demand in agroecosystems. A three‐year experiment was conducted to assess the feasibility of applying N on forage grass cover crops before termination {Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. Ex A. Rich) Stapf] and Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins [syn. B. ruziziensis (R. Germ. and C.M. Evrard)]}, or on forage grass cover crop residues immediately before maize (Zea mays L.) seeding, aiming to supply N to the following maize crop. Urochloa brizantha had 25% higher biomass production and a higher amount of nutrient content than U. ruziziensis. The N application before termination increased biomass production and nutrient content in cover crop residues compared with the conventional fertilization method (30 kg N ha−1 in the maize seeeding plus 170 kg N ha−1 sidedressed in V6 growth stage). Nitrogen applied one day before seeding (DBS) of maize or using conventional method resulted in a higher number of ears per plant and more kernels per ear as well as a higher grain yields of maize (13.8 and 14.1 Mg ha−1, respectively) compared to N applied on cover crops. Our results suggest that, while both forage grass cover crops produced greater amounts of dry matter (DM) and released similar amounts of nutrients, applying all N to cover crops before maize is not a feasible alternative. Nitrogen application 1 DBS could be an alternative management option to supply N to maize because this method resulted in similar nitrogen use efficiency (NUE) as conventional fertilization method.

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