Alencar Junior Zanon

Arranjos de plantas de mandioca e milho em cultivo solteiro e consorciado: crescimento, desenvolvimento e produtividade

The objective of this study was to quantify the growth, development, and yield of cassava and maize in different plant spacings in monocropping and intercropping systems, considering two sowing dates of maize. The experiment was carried out in Santa Maria, RS, Brazil. The cassava variety RS 13 was planted on September 27, 2005. The maize variety BRS Missoes was sown on two dates: November 2, 2005 and November 29, 2005. The experimental design was a complete randomized blocks with 12 treatments and three replications. Growth (plant height and leaf area), development (phyllochron, final leaf number and duration of developmental phases), and yield parameters of both crops were measured. Thermal accumulation (assuming a base temperature of 14 oC for cassava and 10 oC for maize) of some developmental phases and the phyllochron were calculated. Growth and development were not affected by plant spacing in both monocropping and intercropping. The highest land use efficiency was obtained by intercropping cassava and maize, with cassava planted in a double row spacing of 1.6 x 0.5 x 0.6 m and maize in a single row spaced 0.8 x 0.21m or two rows of maize spaced 0.4 x 0.42m between the double rows of cassava, with maize sown on cassava emergence.

Emissão de folhas e início de acumulação de amido em raízes de uma variedade de mandioca em função da época de plantio

The accumulated number of leaves (NF) on the main stem is related to the appearance of several developmental stages in cassava. The beginning of starch accumulation (IAA) in the fibrous roots of cassava switches the source/sink ratio because of the translocation of photoassimilates to the major storage organ in this species. This study was aimed at estimating the phyllochron and identifing a morphological indicator based on NF for IAA in cassava grown in several planting dates. A field experiment was carried out in Santa Maria, RS, Brazil, with four planting dates (28/09, 11/10, 16/11 and 27/12/2005). The variety RS 13 was used and planted in 12 l pots, buried in the soil in a 2.0 x 0.8m spacing. The experimental desing was a completely randomized with 11 replications. Daily degree-days (STd, °C day) were calculated starting at emergency and accumulated by STa = SSTd. IAA was determined on the plants when one root reached a diameter of 0.01m. NF on the date of IAA and the main sterm final leaf number (NFF) up to the first sympodial branches were determined. The plyllochron varied from 20.3 to 29.5°C day leaf -1, with larger values in the two latest planting dates. The NFF varied among planting dates, increasing as planting was delayed. The NF at IAA was similar for the four planting dates and occurred when NF was on average 20.9 (± 1.0) leaves.

Plastocrono e rendimento de feijão-de-vagem cultivado sob ambiente protegido e no ambiente externo em semeadura tardia no outono

Snap bean (Phaseolus vulgaris L.) is a horticultural crop that is enhanced during Fall in Rio Grande do Sul State, which can be favored by growing inside a plastic greenhouse (protected cropping). The estimation of the time interval between the appearance of two successive nodes on a dicot stem, known as plastochron, is important in modeling studies and for crop management. The objective of this study was to evaluate the plastochron and the yield of snap bean grown inside plastic greenhouse (protected environment) and in the open field. An experiment was carried out in Santa Maria, RS, Brazil, during the Fall 2009 in two environments: protected environment (plastic house covered with 100µm of thickness low density polyethylene) and in the open field. Solar radiation, air temperature, thermal time, the main stem node appearance (plastochron) and pod yield were determined. Solar radiation was, 26% lower in the protected environment, and minimum, mean and maximum air temperatures were greater in the protected environment. The plastochron was higher (lower node appearance rate) in the protected environment whereas pod yield was similar in the two environments. The reduction in solar irradiation, caused by the plastic cover, was pointed out as a major cause for the lower node appearance rate (greater plastochron) of the plants in the protected environment whereas reproductive growth in the protected environment was similar to the one in the open field most likely because of the increase in the diffuse fraction of solar radiation that partially compensated the plastic shading, and because of the less plants exposure to possible mechanic stresses as wind and hydraulic during the hottest hours of the day when water demand is the highest.

Contribuição das ramificações e a evolução do índice de área foliar em cultivares modernas de soja

The purposes of this study were to quantify the branches contribution and the leaf area index evolution in modern cultivars of soybean with different maturity groups, stem termination, sowing in different dates and producing regions of soybean in Rio Grande do Sul. Field experiments were conducted during the growing season 2013/2014 in Santa Maria, Julio de Castilhos and in three soybean crops on the municipalities of Restinga Seca, Tupancireta and Agua Santa. It were carried out analysis (occurrence date) of reproductive stages and determination total, maximum, of main stem and of branches of leaf area index in thirteen cultivars of soybean. The leaf area index on the branches contributes with about 31%, 12.3% and 11% of the total leaf area index on the determinate cultivars and with 20.2%, 11.8% and 9% of the total leaf area index on the indeterminate cultivars sowing in September, November and February, respectively, in Santa Maria. Most cultivars showed a reduction on total leaf area index, maximum, of main stem and of branches with the delay on planting date, independently of the maturity group and stem termination.

Influência do fenômeno El Niño na erosividade das chuvas na região de Santa Maria (RS)

O fenomeno El Nino Oscilacao Sul (ENOS) altera o tempo e o clima em varios locais, provocando alteracoes na circulacao atmosferica que afetam os elementos meteorologicos e climaticos, principalmente a chuva, nas diferentes regioes do Brasil. Na regiao Sul do Pais, em anos de El Nino, fase positiva do fenomeno, a chuva e frequentemente acima da normal, e, em anos de La Nina, fase negativa do fenomeno, a chuva e frequentemente abaixo da normal. Algumas caracteristicas das chuvas sao alteradas pelo ENOS, como a frequencia de ocorrencia, a intensidade e a quantidade. Essas caracteristicas sao importantes para a definicao das chuvas erosivas. Entre os metodos de determinacao da erosividade das chuvas, o indice de erosividade EI30 e o mais usado no Rio Grande do Sul (RS). O objetivo deste trabalho foi determinar e associar o indice de erosividade EI30 com o fenomeno ENOS para a regiao de Santa Maria, RS. Usaram-se os dados diarios de chuva registrados em pluviogramas a partir de 1o de julho de 1978 a 30 de junho de 2008, coletados na Estacao Climatologica Principal de Santa Maria, RS. As chuvas individuais e erosivas foram identificadas nos pluviogramas, classificadas em anos de El Nino, La Nina e Neutros, e foi calculado o seu indice EI30. Foi realizada a analise de correlacao de Pearson e analise de regressao entre o EI30 e o Indice Oceânico do Nino (ION). A significância da regressao foi testada com o teste t, a fim de quantificar a associacao entre as duas variaveis, com vistas a possivel previsibilidade do potencial erosivo das chuvas a partir de anomalias de Temperatura da Superficie do Mar (TSM) no oceano Pacifico. Tambem foram classificadas as chuvas em padroes Avancado, Intermediario e Atrasado. O potencial erosivo das chuvas em Santa Maria e afetado pelo fenomeno ENOS, de modo que maior numero de chuvas tem maior potencial erosivo em anos de El Nino e em anos Neutros. A variabilidade do potencial erosivo das chuvas em Santa Maria e maior nos anos Neutros do que nos anos de anomalia da TSM. O padrao das chuvas e alterado em anos de anomalia da TSM, no sentido de que nos anos de El Nino ha aumento nas chuvas de padrao avancado e em anos de La Nina ha aumento nas chuvas de padrao atrasado; no padrao intermediario, ha diminuicao do numero de chuvas em anos de El Nino e La Nina, em comparacao com anos Neutros. A capacidade preditiva do potencial erosivo das chuvas em Santa Maria pelo indice ION e fraca.

Desenvolvimento de cultivares de soja em função do grupo de maturação e tipo de crescimento em terras altas e terras baixas

O objetivo deste trabalho foi caracterizar o desenvolvimento de cultivares de soja com diferentes grupos de maturacao e tipos de crescimento em terras altas e terras baixas no Rio Grande do Sul. Foram conduzidas nove epocas de semeadura em Santa Maria (ambiente de terras altas) e uma epoca de semeadura em Capao do Leao (ambiente de terras baixas) durante os anos agricolas 2010/2011, 2011/2012 e 2012/2013, com 11 cultivares de soja. O delineamento experimental em todos os experimentos foi blocos ao acaso, em parcelas subdivididas. Foi quantificada a duracao, em oC dia, do ciclo de desenvolvimento, da fase vegetativa e reprodutiva, e do periodo entre a data que ocorreu o inicio do florescimento e o numero final de nos para todas as epocas e locais de semeadura. Houve reducao da duracao da fase reprodutiva, do ciclo total de desenvolvimento (exceto algumas cultivares semeadas em setembro), com o atraso da data de semeadura independentemente do grupo de maturacao e tipo de crescimento. As semeaduras de setembro, janeiro e fevereiro promovem uma reducao da fase vegetativa na maioria das cultivares quando comparadas com a epoca recomendada (novembro e dezembro). Cultivares indeterminadas apresentam um maior periodo de sobreposicao das fases vegetativa e reprodutiva do que as cultivares determinadas em todas as epocas e locais de cultivo. O desenvolvimento da soja e similar quando cultivada em terras altas e terras baixas.

Transpiration and leaf growth of potato clones in response to soil water deficit

Potato (Solanum tuberosum ssp. Tuberosum) crop is particularly susceptible to water deficit because of its small and shallow root system. The fraction of transpirable soil water (FTSW) approach has been widely used in the evaluation of plant responses to water deficit in different crops. The FTSW 34 threshold (when stomatal closure starts) is a trait of particular interest because it is an indicator of tolerance to water deficit. The FTSW threshold for decline in transpiration and leaf growth was evaluated in a drying soil to identify potato clones tolerant to water deficit. Two greenhouse experiments were carried out in pots, with three advanced clones and the cultivar Asterix. The FTSW, transpiration and leaf growth were measured on a daily basis, during the period of soil drying. FTSW was an efficient method to separate potato clones with regard to their response to water deficit. The advancedclones SMINIA 02106-11 and SMINIA 00017-6 are more tolerant to soil water deficit than the cultivar Asterix, and the clone SMINIA 793101-3 is more tolerant only under high solar radiation.

Desenvolvimento vegetativo em diferentes hastes da planta de mandioca em função da época de plantio

Studies on the vegetative development of cassava grown in subtropical conditions of Brazil are scarce. The objective of this study was to determine the phyllochron and the final leaf number on the main stem and on sympodial branches of a cassava variety grown in different planting dates in a subtropical climate. A field experiment was conducted in Santa Maria, RS, with four planting dates: 09/26/2006, 10/18/2006, 11/08/2006 and 11/28/2006. The variety FEPAGRO RS13, with tricotomic growth habit, was used in a complete randomized design with four treatments (planting dates) and four 4.0 x 9.0m plots with five rows and 0.8 x 0.8m spacing in each planting date. On the main stem (MS) and on the first order (BR1) and second order (BR2) sympodial branches of six plants per plot randomly selected, the number of visible leaves (NL) on a weekly basis, and the final leaf number (FLN) were measured. The phyllochron on MS, BR1 and BR2 was estimated by the inverse of the slope of the linear regression of NL against accumulated thermal time, assuming a base temperature of 14°C. Phyllochron increased in the sequence MS BR1>BR2. Both phyllochron and FLN varied according to planting date, with photoperiod being a possible cause of such variation. Within BR1 and BR2 sympodial branches, phyllochron and FLN were not different among stems.

Limite crítico no solo para transpiração e crescimento foliar em mandioca em dois períodos com deficiência hídrica

A cassava crop is often exposed to more than one period of water deficit during the growing season. The objective of this study was to verify if there is a difference in the FTSW (fraction of transpirable soil water) threshold for transpiration and leaf growth in cassava plants subjected to one or two periods of water deficit. Two experiments with cassava (Fepagro RS 13 cultivar) were conducted. Treatments were four soil water regimes subdivided into two periods, period 1 (P1) and period 2 (P2): water regimes WR1 and WR2 (with water deficit in both periods and without water deficit in both periods, respectively), and water regimes WR3 and WR4 (with water deficit only in P1 or P2, respectively). The FTSW approach was used to indicate the threshold for transpiration and leaf growth. The FTSW threshold was 0.35, 0.38, and 0.37 for leaf growth and 0.28, 0.26, and 0.28 for transpiration in P1 of WR2 and WR3 and P2 of WR4, respectively. In P2 of WR2, the FTSW threshold for leaf growth and transpiration was 0.09 and 0.13, respectively. It was concluded that there is a decrease in the FTSW threshold in cassava during the second period compared to the first period of soil water deficit, which can be explained by the smaller leaf area, which allowed a longer leaf turgor period, thus delaying activation of the stomata control mechanisms. The practical implication of these results is that they can be used as parameters for crop irrigation, as well as for selecting cultivars more tolerant to water deficit.

Efeito do espaçamento de plantio no crescimento, desenvolvimento e produtividade da mandioca em ambiente subtropical

The objective of this study was to analyze the effect of different planting spacings on the growth, development and stems and roots yield in a subtropical environment of Rio Grande do Sul, Brazil. Treatments consisted of four spacings: 0.8x0.8 m, 1.0x1.0 m, 1.2x1.2 m, 1.5x1.5 m, corresponding to densities of 15,625 plants ha -1 -1 , respectively. The cultivar used was Fepagro - RS 13. The variables of growth and development analyzed were green leaf area, plant height, number of senesced leaves, internode lenght, final leaf (FLN), number of lateral shoots, final size of leaves, phyllochron and stem and root fresh and dry weight yield. The maximum leaf area index and phyllochron increases as plant density increases. The final leaf size and number of lateral shoots increases as plant density decreases. The FLN differed only for the second sympodial branching, with the largest number of leaves in the 1.5x1.5m plant spacing. The stems yield of cultivar Fepagro - RS 13 does not vary with the planting spacing, but tuber root yield per area is higher at higher densities, while yield per plant and per root is higher in lower densities.