E. F. Coelho

Root distribution and water uptake patterns of corn under surface and subsurface drip irrigation

Information on root distribution and uptake patterns is useful to better understand crop responses to irrigation and fertigation, especially with the limited wetted soil volumes which develop under drip irrigation. Plant water uptake patterns play an important role in the success of drip irrigation system design and management. Here the root systems of corn were characterized by their length density (RLD) and root water uptake (RWU). Comparisons were made between the spatial patterns of corn RWU and RLD under surface and subsurface drip irrigation in a silt loam soil, considering a drip line on a crop row and between crop rows. Water uptake distribution was measured with an array of TDR probes at high spatial and temporal resolution. Root length density was measured by sampling soil cores on a grid centered on crop row. Roots were separated and an estimation of root geometrical attributes was made using two different image analysis programs. Comparisons of these programs yielded nearly identical estimates of RLD. The spatial patterns of RWU and RLD distributions, respectively normalized to the total uptake and root length, were generally similar only for drip line on a crop row, but with some local variations between the two measures. Both RLD and RWU were adequately fitted with parametric models based on semi-lognormal and normal Gaussian bivariate density functions (Coelho and Or, 1996; Soil Sci. Soc. Am. J. 60, 1039–1049).

Flow and uptake patterns affecting soil water sensor placement for drip irrigation management

The nonuniform water distribution patterns about drippers make soil water sensor placement a key factor in the performance of soil water-based drip irrigation scheduling schemes. Many of the available guidelines for sensor placement were empirically determined from site and crop specific experiments. The uncertainty in these sensor locations may be large due to the high sensitivity of such point measurements to minute variations in wetting and uptake patterns. The objective of this study was to apply general and physically based principles to the problem of sensor placement in wetted soil volumes under various drip irrigation scenarios. Because a proper selection of sensor placement hinges on accurate description of soil water dynamics, a semi-analytical model for predicting flow and uptake patterns using a few parameters was employed. The effect of various scenarios considering practical irrigation intervals and different growth stages were simulated to test their effect on sensor placement. The sensitivity of point measurements to variability may be reduced by using volume-averaged soil water status. Results illustrate the importance of soil water dynamics on the resultant thresholds at various positions. Regions deemed suitable for sensor placement are influenced mostly by the irrigation interval and less by crop growth stage. High uptake intensity by plant roots renders some regions within the wetted volume unsuitable for tensiometric monitoring.

Influência da salinidade sobre o crescimento, absorção e distribuição de sódio, cloro e macronutrientes em plântulas de maracujazeiro-amarelo

The presence of sodium (Na) and chloride (Cl) in growth medium have leaded to crop growth due to because of negative effects of these ions such as changes in plant capacity of uptake, transport and use of essential nutrients. The objective of this work was to evaluate the influence of salinity on growth, uptake and transport of Na, Cl and macronutrients in yellow passion fruit plants. Three levels of NaCl (0, 50 and 100 m mol L-1) were tested. Experiment was finished after 50 days of growing in 2.2 dm3 pots. It was noticed that height, leaf number, leaf area and dry mass of all parts of the plant were reduced by salinity. The concentration of Na and Cl ions increased with the increasing of salinity. However, ions were retained partially in roots (Cl) and in older leaves (Na). Concentration of nitrogen (N), phosphorous (P) and calcium (Ca) were not affected by salinity. Actually, concentration of potassium (K) was reduced in all parts of the plant while sulfur (S) was reduced only in roots. Based upon the short reduction on growth characteristics, it was concluded thatyellow passion fruit crop has a moderated tolerance to saline stress.

Distribuição de raízes de mamoeiro sob diferentes sistemas de irrigação localizada em latossolo de tabuleiros costeiros

O sistema radicular de uma planta e responsavel pela absorcao de agua do solo e deve ser considerado nos calculos da quantidade de agua necessaria para irrigacao. O trabalho teve por objetivo definir a distribuicao do sistema radicular do mamoeiro irrigado por gotejamento e microaspersao em solo de Tabuleiro Costeiro do Reconcavo Baiano. Foram feitas duas trincheiras em diferentes posicoes relativas a duas plantas irrigadas por microaspersao e gotejamento superficial e enterrado a 0,25 m, com as linhas laterais junto a fileira de plantas, com dois gotejadores por planta, cada um a 0,40 m de distância das mesmas. Na microaspersao, usou-se um emissor para duas plantas, entre duas fileiras simples. As amostras de raizes foram extraidas em malha de pontos nessas trincheiras de forma a abranger uma secao completa do sistema radicular. As raizes foram separadas do solo e digitalizadas em computador, sendo as imagens processadas por um aplicativo computacional que estimou o comprimento total e o diâmetro medio das mesmas em cada posicao no perfil. O sistema radicular ocupou maior volume de solo na microaspersao em relacao ao gotejamento, com maior concentracao das raizes na direcao do microaspersor. A profundidade efetiva do sistema radicular do mamoeiro irrigado por gotejamento superficial ou enterrado foi de 0,45 m e na microaspersao variou de 0,15 m na direcao perpendicular a fileira de plantas a 0,35 m entre a planta e o microaspersor.

Produção e partição de matéria seca e abertura estomática do limoeiro 'Cravo' submetido a estresse salino

This research aimed to evaluate the influence of the salinity on some physiological parameters in Rangpur lime (Citrus limonia Osbeck), which is the principal citrus rootstock in Bahia. The importance of this study is based on the possibility of using water of low quality for irrigation, which is a production constraint for citrus crop. Rangpur lime seeds were selected by size and sowed in washed sand. Three days after the germination, the seedlings were transferred to plastic pots containing nutrient solution. After ten days, the saline treatments were applied by addition of NaCl to the growth solution in each pot, reaching the final concentrations of 0, 20, 40 and 80 mM of NaCl. The completely randomized experiment had four treatments (NaCl concentration) and five replications. Forty two days after the beginning of the saline stress the experiment was concluded. The salinity decreased total dry matter production of the stem and roots. In the intermediate levels of NaCl (20 and 40 mM), neither the leaf area nor the leaf dry matter were affected; those characters were only affected in the level of 80 mM. The increase of the salinity levels caused reduction in the root:canopy ratio, in the stomatal conductance, in the transpiration and in the leaf temperature.

Estimating water application efficiency for drip irrigation emitter patterns on banana

The objective of this work was to evaluate root and water distribution in irrigated banana (Musa sp.), in order to determine the water application efficiency for different drip irrigation emitter patterns. Three drip emitter patterns were studied: two 4-L h -1 emitters per plant (T1), four 4-L h -1 emitters per plant (T2), and five 4-L h -1 emitters per plant (T3). The emitters were placed in a lateral line. In the treatment T3, the emitters formed a continuous strip. The cultivated area used was planted with banana cultivar BRS Tropical, with a 3-m spacing between rows and a 2.5-m spacing between plants. Soil moisture and root length data were collected during the first production cycle at five radial distances and depths, in a 0.20x0.20 m vertical grid. The experiment was carried out in a sandy clay loam Xanthic Hapludox. Soil moisture data were collected every 10 min for a period of five days using TDR probes. Water application efficiency was of 83, 88 and 92% for the systems with two, four and five emitters per plant, respectively. It was verified that an increase in the number of emitters in the lateral line promoted better root distribution, higher water extraction, and less deep percolation losses.

Freqüência de irrigação em meloeiro cultivado em solo arenoso

The objective of this work was to evaluate the effect of five irrigation frequencies in the productivity and efficience of water use of melon crop cultivated under fertirrigation by drip irrigation in a sandy soil of the Coast Plains of Piaui, Brazil. The experiment was allocated in a randomized complete block design, with five treatments and six replications. The treatments were: F1, F2, F3, F4 and F5, irrigation frequency of 0.5, 1, 2, 3 and 4 days, respectively. The irrigation frequency affected the marketable and total yield of the melon crop. The highest total (70.73 t ha-1; 77.99 t ha-1 and 64.21 t ha-1) and marketable (62.20 t ha-1; 63.88 t ha-1 and 53.67 t ha-1) yields were obtained with the frequencies of 0.5 and 1 day, respectively. It was observed that for the leastest frequent of water applications there was a significative reduction (P<0.01) of the marketable and total fruit yield of melon crop. The average fruit weight was not affected by the frequency of water application. The highest and the lowest efficiency of water use, 24.40 kg m-3 and 14.14 kg m-3, were obtained with the frequencies of F1 and F5, respectively. The irrigation frequency twice a day, daily and two days are indicated for melon crop cultivated in sand soil by drip irrigation. The efficiency of water use for the melon crop is higher when the irrigation frequencies are higher.

Regulated deficit irrigation and tommy atkins mango orchard productivity under microsprinkling in brazilian semi arid

This study aimed to test controlled levels of water deficiency in soil in mango trees, under microsprinkling irrigation, in semi-arid conditions, and to evaluate its effect in the productivity and fruits quality. The deficits were applied in the phases I, II and III of growth of the fruit, during the productive cycles of the mango tree in 2006 and 2007. The experiment in both cases was arranged in an entirely random design with 10 treatments and 3 repetitions, in the year I, and with 8 treatments and 3 repetitions in the year II. The values of soil water potential, of the treatments submitted to regulated deficit irrigation (RDI), were placed in the range of 0 to -0.011 MPa, showing that the soil humidity varied between the saturation and the field capacity, not characterizing deficit water condition. The average values of stem water potential (Ψstem) varied between -0.90 and -1.74 MPa, evidencing significant effect (p <0.05) just for T1 (without irrigation), T7 and T8 (RDI with 30% of the ETc in the phases II and III, respectively). Through the variance analysis, significant differences were not verified among productivity, number of fruits per plant and size of the fruit, in none of the experiments, what indicates the possibility of reduction of the water use in the irrigation of the mango tree without significant losses of productivity and fruit quality.

Desempenho de diferentes guias de ondas para uso com o analisador de umidade TRASE

O trabalho teve como objetivo avaliar a relacao entre a umidade e a constante dieletrica aparente do solo e diferentes guias de onda para uso com o analisador de umidade Trase, que opera de acordo com o principio da reflectometria no dominio do tempo - TDR. Amostras indeformadas e deformadas de duas manchas de textura diferente de um Latossolo Amarelo Distrofico foram retiradas do campo e acondicionadas em recipientes de 10 L, perfazendo quatro repeticoes para cada textura e estrutura. Foram construidas tres diferentes guias de onda, com hastes de 0,15 m, sendo uma com capacitor e uma sem capacitor no inicio da guia, com espacamento de 0,009 m entre hastes e outra sem capacitor, com espacamento de 0,022 m entre hastes. Essas guias de onda, juntamente com guias originais do fabricante com hastes de 0,20 m, espacadas 0,022 m, foram inseridas individualmente em cada recipiente. Dados de umidade obtidos gravimetricamente e pelo analisador TRASE, e da constante dieletrica, foram tomados usando-se todas as guias de onda em cada recipiente durante a secagem do solo, de 0,35 m3 m-3 a 0,10 m3 m-3. Tres modelos matematicos foram ajustados aos dados de umidade e da correspondente constante dieletrica do solo gerados pelas guias de onda do fabricante. Um modelo exponencial foi considerado como mais adequado para estimativas dos teores de agua, em funcao da constante dieletrica para a guia de onda do fabricante. Todas as guias de onda avaliadas apresentam viabilidade de uso, desde que previamente calibradas.

Desempenho de modelos de calibração de guias de onda acopladas a TDR e a multiplexadores em três tipos de solos

The study aimed at evaluating of calibration models for two kinds of TDR waveguides used with Trase System and TDR 100 equipments linked to the cable tester or the multiplexer. Disturbed samples of three soils were packed in PVC columns and, after soil saturation, two TDR waveguides of three rods with capacitor and with resistor were inserted into the soil columns. The waveguides were connected to two TDR equipments (Trase System and TDR 100), directly to the cable tester or a multiplexer. Soil water content data by gravimetry were collected during the drying process from saturation to values close to the lowest limit of water availability. The readings were performed with TDR probes connected to the cable tester and the multiplexer. A mathematical model was fitted to the bulk dielectric constant (e) and water content data (q) and the performance of five models to obtain q as a function of e was evaluated. Results showed that there was no significant difference between the TDR Trase System capacitor waveguide calibration connected either directly to the water content analyzer or the multiplexer channel. In case of TDR 100 using waveguides with resistor, the calibration has to be performed according to the connection of the waveguide to the water content analyzer or the multiplexer channel. The cubic calibration model performed best, followed by the Roth model, which estimated the values of bulk dielectric constant and water content well with a closer to 0.5 for waveguides with capacitor than for waveguides with resistor.