Francisco Valderez Augusto Guimarães

Acumulação de biomassa e extração de nutrientes por plantas de feijão-de-corda irrigadas com água salina em diferentes estádios de desenvolvimento

Due to the limited availability of low salinity waters, the use of water of moderate to high salinity in agriculture is a close reality in the expansion of irrigated farms. The objective of this research was to evaluate the effect of irrigation with saline water, applied at different development stages of cowpea plants, on growth and nutrient uptake. The experiment was set up in the field during the dry season. A completely randomized block design, with five treatments and five replications was adopted. The treatments studied were: T1 - groundwater with electrical conductivity (ECw) of 0.8dS m-1 during the whole crop cycle; T2 - saline water (ECw = 5.0dS m-1) during the whole crop cycle; T3, T4 and T5 - saline water from 0 to the 22nd day after sowing (DAS), from the 23rd to the 42nd DAS and from the 43rd to 62nd DAS, respectively. The plants subjected to T3, T4 and T5 were irrigated with groundwater in the other stages of the crop cycle. At 8, 23, 43 and 63DAS plants were collected for evaluation of plant growth, Na, Cl, K, Ca, N, P, Fe, Cu, Zn and Mn contents and distribution in plant parts. The application of saline water during the whole crop cycle (T2) and during the germination and initial plant development (T3) caused, respectively, inhibition and retardation of plant growth. Cowpea plants removed the minerals in the following decreasing sequence: N > K > Cl > Ca > Na > P > Fe > Mn > Zn > Cu, but the continuous use of saline water (T2) reduced the total uptake of all nutrients, except for Na. The minerals Na, Cl, K, Ca, Fe and Mn were distributed preferentially in the vegetative parts of the plant, while most of the N and P were translocated to the pods.

Morpho-physiological responses of cowpea leaves to salt stress

The effect of salt stress of known intensity and duration on morpho-physiological changes in leaves of different ages from cowpea [Vigna unguiculata (L.) Walp.] plants was studied, aiming for a better understanding of the acclimation process of the whole-plant. Seeds were sown in vermiculite and seedlings were transferred to plastic trays containing aerated nutrient solution, and kept in a greenhouse. When the first trifoliate leaf emerged the seedlings were transplanted into 3 L plastic pots containing aerated nutrient solution. Salt additions started 5 d later, and the salt-treated plants received 25 mmol L-1 per day until reaching a final concentration of 75 mmol L-1. During the experimental period primary leaves and the 1st, 2nd, and 3rd trifoliate leaves were used for measurements of net photosynthesis, leaf area, leaf succulence, specific leaf mass, ions and chlorophyll concentrations. Growth analysis of the whole-plant was performed at the end of the experimental period. Salinity did not affect net photosynthesis, but reduced dry mass production and the number of lateral branches. Leaf concentrations of Na+, Cl-, K+ and P increased in salt-stressed plants, but these responses were dependent upon stress duration and leaf age. The higher concentration of potentially toxic ions (Na+ and Cl-) in older leaves could contribute to the reduced ion accumulation in growing tissues, but the tendency of K and P accumulation in leaves appeared to be the result of reduced re-translocation, i.e., not related to plant acclimation. Salinity also increased the source/sink ratio, leaf succulence, specific leaf mass, and chlorophyll accumulation per unit of leaf area, suggesting that the observed changes could be part of an integrated mechanism of whole-plant acclimation to salt stress.

Soil salinization and maize and cowpea yield in the crop rotation system using saline waters

A utilizacao de aguas salinas bem como o reuso de aguas de drenagem na irrigacao dependem de estrategias de longo prazo que garantam a sustentabilidade socioeconomica e ambiental dos sistemas agricolas. Neste trabalho, avaliaram-se os efeitos da irrigacao com agua salina na estacao seca e com agua de baixa salinidade na estacao chuvosa sobre o acumulo de sais no solo e a produtividade de milho e feijao-de-corda em sistema de rotacao. O experimento foi conduzido em campo, utilizando-se do delineamento em blocos ao acaso, com cinco repeticoes. O primeiro cultivo foi instalado durante a estacao seca de 2007, com a cultura do milho irrigada com agua de diferentes salinidades (0,8; 2,2; 3,6 e 5,0 dS m-1). As plantas foram coletadas aos 90 dias apos a semeadura (DAS), sendo realizadas as avaliacoes: crescimento vegetativo, producao de graos por planta, materia seca de 1.000 graos e produtividade. Durante a estacao chuvosa de 2008, foi cultivado o feijao caupi nas mesmas parcelas que foram cultivadas com milho. Ao final do ciclo, as plantas foram coletadas, sendo realizadas avaliacoes de crescimento vegetativo e produtividade. Amostras de solo foram coletadas antes e apos o cultivo do milho e ao final do cultivo com feijao caupi. A salinidade da agua de irrigacao acima 2,2 dS m-1 reduziu a produtividade do milho durante o periodo seco. Os elevados totais de precipitacao pluviometrica durante a estacao chuvosa proporcionaram a lixiviacao dos sais acumulados durante o cultivo na estacao seca e eliminaram os possiveis efeitos negativos da salinidade sobre o feijao caupi. Porem, o feijao caupi apresentou um comportamento atipico com uma expressiva proporcao de massa vegetativa e baixa producao de vagens, o que reduziu a eficiencia dessa estrategia de rotacao de culturas, nas condicoes do presente estudo.

Trocas gasosas e teores de minerais no feijão-de-corda irrigado com água salina em diferentes estádios

The objective of this paper was to evaluate the effect of irrigation with saline water, applied at different development stages of cowpea, on gas exchange, growth and nutrient concentration. The experiment was set up in the field, in a completely randomized block design, with five treatments and five repetitions. The treatments studied were: T1 - Groundwater with electrical conductivity (ECw) of 0.8 dS m-1 during the whole crop cycle (control); T2 - saline water (ECw = 5.0 dS m-1) during the whole crop cycle; T3, T4 and T5 - saline water from 0 to 22nd day after sowing (DAS), from the 23rd to the 42nd DAS and from the 43rd to 62nd DAS, respectively. The plants of T3, T4 and T5 were irrigated with groundwater in the remaining stages of the crop cycle. During the crop cycle, the gas exchange in leaves, dry mass production and mineral concentrations (Na+, Cl-, K+, Ca2+, N and P) were determined. The treatments T2 and T3, as compared to T1, reduced the net photosynthesis and transpiration, the absolute and relative growth rates, and caused an increase in Na+ and Cl- concentrations. However, in the plants belonging to the T3 treatment, recovery was observed for all these variables. The changes in Na+ and Cl- concentration in plants of T4 and T5 were not sufficient to provoke significant effects in gas exchange and on plant growth.

Mineral nutrition and extraction of nutrients by corn plant irrigated with saline water

The use of saline water in irrigated agriculture can cause nutritional imbalance and competitive inhibition in the absorption of nutrients. The objective of this study was to evaluate the effects of salinity of irrigation water on the accumulation, the total absorption, and the distribution of mineral elements in maize plants. The study was conducted under field conditions in an Yellow Red Argisol in the dry season, in the randomized blocks design with five replicates during September to December 2007 in Fortaleza - CE. The maize plants were collected at 90 days after sowing, and the following assessments were made: content, extraction and distribution of mineral elements in the plant parts (leaf, stem, grain and elderberry). The increase of salinity of irrigation water at 90 days after sowing inhibited the accumulation of potassium in leaves, and corn stan and phosphorus in the grains. The extraction of nutrients and sodium by plants irrigated with saline water ranging from 0.8 to 3.6 dS m-1 had the following decreasing order: K > Mg > Ca > P > Na; the treatment of higher salinity (5.0 dS m-1) the sequence extraction was: K > Ca > Na > P > Mg.

Supplemental Ca2+ does not improve growth but it affects nutrient uptake in NaCl-stressed cowpea plants

The growth and nutrient assimilation was evaluated in CaCl2- and CaSO4-supplemented cowpea plants subjected to salt stress (75 mM NaCl). The salinity significantly reduced the cowpea vegetative growth. The addition of CaCl2 in the growth medium did not significantly affect plant growth, while for the CaSO4, the beneficial effects of Ca2+ were moderate. Salinity increased the Na+, K+, Cl-, N and P content in the plants, however it decreased the content of Ca2+ and Mg2+. Increases in Ca2+ concentration in the nutrient solution caused decreases in the Na+ and Mg2+ contents and increases in Ca2+, K+, P, and Cl- contents. The supplemental Ca2+ may alleviate the Na+ toxicity and may improve nutritional and ionic balance in cowpea, but it cannot overcome the osmotic effects associated with the increased total salt concentration.

Colonização micorrízica arbuscular e tolerância ao mal-do-Panamá em mudas de banana-maçã

The aim of this study was to evaluate the effect of the colonization of arbuscular mycorrhiza on the tolerance to Panama disease of the banana plant cv. maca under different sources of nutrients. A completely randomized design was employed, having a 2 x 4 factorial [2 densities of native FMA spores (D1 - 3,500 spores kg-1 soil and D2 - 7000 spores kg-1 soil) and four different concentrations of nutrient sources - three of a nutrient solution (SN 40%, SN 70% and SN 100%) and a 100% solution of bio-fertiliser (B4)], with three replications. After planting, the seedlings were inoculated with Fusarium oxysporum f.sp. cubense, and later the shoot dry matter, leaf phosphorus content, mycorrhizal colonization, soil pH and disease severity index were evaluated. The different nutrient sources affected the shoot dry matter, the phosphorus content, the mycorrhizal colonization and the disease severity index, but did not affect the pH of the soil-solution. The bio-fertiliser did not meet the nutritional demands of the plants, which remained underdeveloped, however it promoted intense mycorrhizal colonization and lower manifestations of fusarium. The latter increased under mineral fertilization.