Rubens Duarte Coelho

Response of Tanzania grass to nitrogen and irrigation depth. I: Production of forage

With the objective to study the effect of total depth of water, nitrogen fertilization and their interaction on the growth factors, production, efficiency of use and forage quality as well as to determine production functions for total, foliar and stem dry matter of Tanzania grass (Panicum maximum cv. Tanzania) with the intention to obtain level of maximum and economic production of each analyzed production factor. The experiment was carried out in split-split-plot, where in the main plots the different irrigation levels were distributed (0, 30, 70,100 and 150% of field capacity (FC)), in the split plot the levels of nitrogen (0, 100, 275, 756 and 2079 kg N ha-1 year-1) and in the split-split plot the three climatic periods (summer, winter and spring). The higher irrigation regimes provided negative effects on the production of dry matter. The use of nitrogen levels above 756 kg N ha-1 year-1 did not show effect on the production of dry matter, the increments in the total and foliar production of dry matter for the levels of 100, 275, 756 and 1.769 kg N ha-1 year-1 were 15, 19, 29 and 20% (16% foliar), respectively.

Ocorrência de entupimento de origem biológica em sistema de irrigação por gotejamento

O trabalho consistiu de uma avaliacao da uniformidade de distribuicao de agua em uma parcela de um sistema de irrigacao por gotejamento para producao de flores em estufa, com 5 anos de uso, em uma propriedade no municipio de Atibaia, SP. Em uma amostra de 25 gotejadores retirados da parcela, determinou-se, em laboratorio, a curva de vazao-pressao e o coeficiente de variacao de fabricacao, CV, para as pressoes de 50, 100, 150, 200, 250, 300, 350 e 400 kPa. Analises quimica, fisica e de contagem bacteriologica da agua foram realizadas em tres pontos do sistema de irrigacao: na fonte de agua, apos o sistema de filtragem e no final de uma linha de gotejadores no meio da parcela avaliada. O valor do CV foi de 8,2% e os valores de 73% para o coeficiente de uniformidade de aplicacao de agua, 97% para o coeficiente de uniformidade hidraulica e 26% para o coeficiente de performance do emissor, juntamente com os resultados das analises da agua, permitiram evidenciar-se a ocorrencia de entupimento de origem biologica afetando a uniformidade de aplicacao de agua do sistema.

Transpiração de plantas jovens de laranjeira 'valência' sob porta-enxerto limão'cravo' e citrumelo 'swingle' em dois tipos de solo

The total citrus area irrigated in Brazil has increased over the decades. The main cause of this increasing is due to the use of rootstocks tolerant to Citrus Sudden Death however they are less tolerant to drought than Rangpur lime. This research aims to study the influence of rootstock and soil type on transpiration of young plants of Valencia orange. The experiment was conducted in a greenhouse at the Department of Biosystems Engineering, ESALQ / USP. Orange seedlings were planted in boxes of 500 L. It was determined simultaneously sweating of 20 plants through thermal dissipation probes (sap flow). It was monitored solar radiation, relative humidity and air temperature sensors were installed to 2 m tall at the center of the greenhouse. The reference evapotranspiration (EToPM) was calculated by the standard method suggested by FAO. According to these results it is concluded that plant transpiration of Valencia oranges are influenced not only by the type of rootstock but also by leaf area growth and phenological stage, and its relationship with EToPM is not linear in the whole range of evaporative demand of the atmosphere.

Net melon performance as affected by the drip irrigation depth and mulching

The modern techniques of water supply through irrigation can substantially reduce water waste, which contributes to attend the enlarging water demand. The objective of this work was to study the influence of subsurface drip irrigation and mulching over melon yield and quality characteristics, in a sandy soil (Typic Hapludox). The experimental design was blocks at random, with four replications. Treatments were displayed in a 2 x 3 factorial (with and without mulching x surface and 0.20 and 0.40 depth subsurface drip irrigation). Mulching using double-sided silver/black film increased fruit average mass, plant production, yield, daily growth rate for plant height and crown diameter, fruit distal diameter, and pulp thickness. The subsurface drip irrigation at 0.20 m depth resulted in larger fruit average mass, plant production, and yield than surface and 0.40 m depth drip irrigation.

Distribuição espacial de pivôs centrais no Brasil: I - região sudeste

Irrigated areas by state and by irrigation method is the available information about irrigation in Brazil. Distribution inside the states, number or size is not easily found even through the industry. These data are very important when one intends to study water availability or growth potencial of irrigated areas for a specific site due to the increasing concern about drinking water worldwide and nationally. The present study had the objective to collect such information using satellite images from Landsat based on the intrinsic characteristic of the center pivot equipments, the circular mark on landscape easily visible. With comparison the geo-referenced images and its articulation with the official IBGE maps, it was possible to draw the state maps with the equipment density distribution, which, when compared to other available sources permitted to validate the methodology used for this purpose.

Simulating wind effect on microsprinkler water distribution

Wind incidence can affect microsprinkler water distribution. Evaluations of those conditions can be facilitated using simulations by computational models. The present work evaluates the performance of a ballistic model on simulating the wind effect on microsprinkler water distribution. Experimental tests were carried out using self-compensating microsprinklers, nozzle sizes 1.00 mm (gray), 1.10 mm (brown), 1.48 mm (orange), and 1.75 mm (yellow). The gray and brown nozzles used black swivels and the orange and yellow nozzles used blue swivels. The wind effect was artificially caused by fourteen 200 W fans. Computational simulations were realized using SIRIAS software, based on a ballistic model originally developed for sprinkler systems. The correlation coefficients (r) varied from 0.619 to 0.880, while the exactness coefficients (d) varied from 0.842 to 0.944. Swivels internal geometry influenced results. Tested models presented performances classified as very good for the black swivel nozzles and regular for the blue swivel nozzles.

Entupimento de gotejadores e seu efeito na pressão da rede hidráulica de um sistema de microirrigação

The present study attempts to evaluate the pressure increase in the hydraulic network of a micro-irrigation system when partial or total clogging of emitters occurs. The evaluated area was of 280 ha, with citrus irrigation based on subsurface auto-compensating drippers. The methodology utilized a mathematical model based on Bernoullis equation, simulating the effects of different clogging rates on the network pressure. To evaluate the pressure variation in the system, the obstructions in the range from 0 to 100% were simulated. For the condition of 50% clogging, 80% of the total pipeline length presented hydraulic pressure more than the nominal pressure foreseen in the project. The mathematical model permitted the simulation of: (a) the variation of the motor-speed of the pump (diesel energy), as a possible solution for controlling the excess pressure problem due to clogging (b) the pressure increase in the network with rotation in excess caused by tachometer imprecision or labor misconduct. When the clogging of 50% of the emitters was simulated with the motor-speed under 2100 rotation min-1, 98% of the pipeline of the system developed pressures in excess of the normal range.

Water infiltration in the soil: part I cylinder infiltrometer versus sprinkler infiltrometer.

The objective of this paper was to compare values of water infiltration rate in soil, obtained with two distinct methodologies: cylinder infiltrometer and sprinkler infiltrometer. Thirty six infiltration rate curves were obtained using the cylinder infiltrometer methodology and four infiltration rate curves using a sprinkler infiltrometer. It was observed that the arithmetic mean of results from the cylinder infiltrometer methodology obtained overestimated the infiltration rate obtained with sprinkler infiltrometer and that the geometric mean and mode of the results obtained with cylinder infiltrometer approached the velocity of infiltration of water in soil obtained with the sprinkler infiltrometer.

Suscetibilidade de gotejadores ao entupimento de causa biológica

An experiment was conducted with the objective of evaluating the resistance of different dripper designs for biological clogging. Five kinds of drippers: Streamline 100, Ram 17L, Dripline 2000, Tiran 17 and Typhoon 20 were evaluated. The statistical design used was a completely randomized block in a split plot, composed of 5 treatments (dripper model) in the main plot and operation time (9 levels) in the sub plot with 4 replications. A regular water source for irrigation equipment was used with some bacterial genus and presenting a bacterial population of about 50,000 UFC mL-1. In every 240 h the flow of each emitter was measured. The total operation time was 2160 h. The results showed that there were differences among the emitters. Ram and Streamline models presented the smaller flow rate reduction while Tiran and Dripline models presented the higher flow rate reduction.

Dynamic blockage of drippers as a function of the application of super simple phosphate and nítric acid in localized irrigation

The super simple phosphate (SS) is an alternative to the phosphorous fertilizers which are used through fertigation, as the phosphoric acid, which triggers acidification of the wetted volume in the soil, and the monophosfato of purified ammonium, that has a higher price. However, the effect of such fertilizer in the emitters function, mainly in the drippers, is not known neither if it is possible to control the blockage for SS through acid applications. Thus, this study was developed in order to evaluate the possibility of the use of super simple phosphate trough drip irrigation, as an alternative to the use of other phosphorous fertilizers, and the attempt of controlling the blockage with nitric acid. The work was carried out in bench of drippers rehearsals, located at the Hydraulic laboratory in ESALQ-USP. Doses of 50; 75 and 100% of the super simple phosphate (SS) were applied in 26 emitter tubes with different commercial marks, and after 360 hours the nitric acid with a pH of 2 was applied, in the attempt of clearing the most sensitive drippers to the blockage. With the results it was possible to infer that: the use of super simple phosphate can be done by fertigation without causing damages to the system and the nitric acid, applied according to this methodology, did not provide the clearance of the emitters.