Design and management optimization of trickle irrigation systems using non-linear programming

A non-linear model is presented which optimizes the lay-out, as well as the design and management of trickle irrigation systems, to achieve maximum net benefit. The model consists of an objective function that maximizes profit at the farm level, subject to appropriate geometric and hydraulic constraints. It can be applied to rectangular shaped fields, with uniform or zero slope. The software used is the Gams-Minos package. The basic inputs are the crop-water-production function, the cost function and cost of system components, and design variables. The main outputs are the annual net benefit and pipe diameters and lengths. To illustrate the capability of the model, a sensitivity analysis of the annual net benefit for a citrus field is evaluated with respect to irrigated area, ground slope, micro-sprinkler discharge and shape of the field. The sensitivity analysis suggests that the greatest benefit is obtained with the smallest microsprinkler discharge, the greatest area, a square field and zero ground slope. The costs of the investment and energy are the components of the objective function that had the greatest effect in the 120 situations evaluated. (C) 1996 Academic Press Limited

Relationship between citrus productivity and indicators of uniformity in trickle irrigation system

In trickle irrigation systems, the design is based on the pre-established emission uniformity (EU) which is the combined result of the equipment characteristics and its hydraulic configuration. However, this desired value of the EU may not be confirmed by the final project (in field conditions) and neither by the yield uniformity. The hypotheses of this research were: a) the EU of a trickle irrigation system at field conditions is equal to the emission uniformity pre-established in the its design; b) EU has always the lowest value when compared with other indicators of uniformity; c) the discharge variation coefficient (VC) is not equal to production variation coefficient in the operational unit; d) the difference between the discharge variation coefficient and the productivity variation coefficient depends on the water depth applied. This study aimed to evaluate the relationship between EU used in the irrigation system design and the final yield uniformity. The uniformity indicators evaluated were: EU, distribution uniformity (UD) and the index proposed by Barragan & Wu (2005). They were compared estimating the performance of a trickle irrigation system applied in a citrus orchard with dimensions of 400m x 600m. The design of the irrigation system was optimized by a Linear Programming model. The tree rows were leveled in the larger direction and the spacing adopted in the orchard was 7m x 4m. The manifold line was always operating on a slope condition. The sensitivity analysis involved different slopes, 0, 3, 6, 9 and 12%, and different values of emission uniformity, 60, 70, 75, 80, 85, 90 and 94%. The citrus yield uniformity was evaluated by the variation coefficient. The emission uniformity (EU) after design differed from the EU pre-established, more sharply in the initial values lower than 90%. Comparing the uniformity indexes, the EU always generated lower values when compared with the UD and with the index proposed by Barragan. The emitter variation coefficient was always lower than the productivity variation coefficient. To obtain uniformity of production, it is necessary to consider the irrigation system uniformity and mainly the water depth to be applied.

Modelling trickle irrigation: Comparison of analytical and numerical models for estimation of wetting front position with time

Irrigation practices that are profligate in their use of water have come under closer scrutiny by water managers and the public. Trickle irrigation has the propensity to increase water use efficiency but only if the system is designed to meet the soil and plant conditions. Recently we have provided a software tool, WetUp (http://www.clw.csiro.au/products/wetup/), to calculate the wetting patterns from trickle irrigation emitters. WetUp uses an analytical solution to calculate the wetted perimeter for both buried and surface emitters. This analytical solution has a number of assumptions, two of which are that the wetting front is defined by water content at which the hydraulic conductivity (K) is I mm day(-1) and that the flow occurs from a point source. Here we compare the wetting patterns calculated with a 2-dimensional numerical model, HYDRUS2D, for solving the water flow into typical soils with the analytical solution. The results show that the wetting patterns are similar, except when the soil properties result in the assumption of a point source no longer being a good description of the flow regime. Difficulties were also experienced with getting stable solutions with HYDRUS2D for soils with low hydraulic conductivities. (c) 2005 Elsevier Ltd. All rights reserved.

Subsurface drip irrigation emitter spacing effects on soil water redistribution, corn yield and water productivity

Emitter spacings of 0.3 to 0.6 m are commonly used for subsurface drip irrigation (SDI) of corn on the deep, silt loam soils of the U.S. Great Plains. Subsurface drip irrigation emitter spacings of 0.3, 0.6, 0.9 and 1.2 m were examined for the resulting differences in soil water redistribution, corn grain yield, yield components, seasonal water use, and water productivity in a 4‐year field study (2005 through 2008) at the Kansas State University Northwest Research‐Extension Center, Colby, Kansas. The results indicate that there is increased preferential water movement along the dripline (parallel) as compared to perpendicular to the dripline and that this phenomenon partially compensates for wider emitter spacings in terms of soil water redistribution. Corn yield and water productivity (WP) were not significantly affected by the emitter spacing with application of a full irrigation regime

The effects of irrigation, nitrogen fertilizer and grain size on Hagberg falling number, specific weight and blackpoint of winter wheat

The effects of irrigation and nitrogen (N) fertilizer on Hagberg falling number (HFN), specific weight (SW) and blackpoint (BP) of winter wheat (Triticum aestivum L) were investigated. Mains water (+50 and +100 mm month(-1), containing 44 mg NO3- litre(-1) and 28 mg SO42- litre(-1)) was applied with trickle irrigation during winter (17 January-17 March), spring (21 March-20 May) or summer (24 May-23 July). In 1999/2000 these treatments were factorially combined with three N levels (0, 200, 400 kg N ha(-1)), applied to cv Hereward. In 2000/01 the 400 kg N ha(-1) treatment was replaced with cv Malacca given 200 kg N ha(-1). Irrigation increased grain yield, mostly by increasing grain numbers when applied in winter and spring, and by increasing mean grain weight when applied in summer. Nitrogen increased grain numbers and SW, and reduced BP in both years. Nitrogen increased HFN in 1999/2000 and reduced HFN in 2000/01. Effects of irrigation on HFN, SW and BP were smaller and inconsistent over year and nitrogen level. Irrigation interacted with N on mean grain weight: negatively for winter and spring irrigation, and positively for summer irrigation. Ten variables derived from digital image analysis of harvested grain were included with mean grain weight in a principal components analysis. The first principal component ('size') was negatively related to HFN (in two years) and BP (one year), and positively related to SW (two years). Treatment effects on dimensions of harvested grain could not explain all of the effects on HFN, BP and SW but the results were consistent with the hypothesis that water and nutrient availability, even when they were affected early in the season, could influence final grain quality if they influenced grain numbers and size. (C) 2004 Society of Chemical Industry

Model to increase the lateral line length of drip irrigation systems

Non-pressure compensating drip hose is widely used for irrigation of vegetables and orchards. One limitation is that the lateral line length must be short to maintain uniformity due to head loss and slope. Any procedure to increase the length is appropriate because it represents low initial cost of the irrigation system. The hypothesis of this research is that it is possible to increase the lateral line length combining two points: using a larger spacing between emitters at the beginning of the lateral line and a smaller one after a certain distance; and allowing a higher pressure variation along the lateral line under an acceptable value of distribution uniformity. To evaluate this hypothesis, a nonlinear programming model (NLP) was developed. The input data are: diameter, roughness coefficient, pressure variation, emitter operational pressure, relationship between emitter discharge and pressure. The output data are: line length, discharge and length of the each section with different spacing between drippers, total discharge in the lateral line, multiple outlet adjustment coefficient, head losses, localized head loss, pressure variation, number of emitters, spacing between emitters, discharge in each emitter, and discharge per linear meter. The mathematical model developed was compared with the lateral line length obtained with the algebraic solution generated by the Darcy-Weisbach equation. The NLP model showed the best results since it generated the greater gain in the lateral line length, maintaining the uniformity and the flow variation under acceptable standards. It had also the lower flow variation, so its adoption is feasible and recommended.

Increasing the lateral line length of drip irrigation systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Energy requirements in pressure irrigation systems

Modernization of irrigation schemes, generally understood as transformation of surface irrigation systems into pressure –sprinkler and trickle- irrigation systems, aims at, among others, improving irrigation efficiency and reduction of operation and maintenance efforts made by the irrigators. However, pressure irrigation systems, in contrast, carry a serious energy cost. Energy requirements depend on decisions taken on management strategies during the operation phase, which are conditioned by previous decisions taken on the design project of the different elements which compose the irrigation system. Most of the countries where irrigation activity is significant bear in mind that modernization irrigation must play a key role in the agricultural infrastructure policies. The objective of this study is to characterize and estimate the mean and variation of the energy consumed by common types of irrigation systems and their management possibilities. The work includes all processes involved from the diversion of water into irrigation specific infrastructure to water discharge by the emitters installed on the crop fields. Simulation taking into account all elements comprising the irrigation system has been used to estimate the energy requirements of typical irrigation systems of several crop production systems. It has been applied to extensive and intensive crop systems, such us extensive winter crops, summer crops and olive trees, fruit trees and vineyards and intensive horticulture in greenhouses. The simulation of various types of irrigation systems and management strategies, in the framework imposed by particular cropping systems, would help to develop criteria for improving the energy balance in relation to the irrigation water supply productivity.

Projecte de reg per degoteig en una plantació de 5,25 ha de vinya a Can Macià (T.M. d’Òdena, comarca de l’Anoia)

Estudi sobre la instal.lació d’un sistema de reg per degoteig i un sistema de fertirrigació a 5,25 ha de vinya amb les corrresponents instal.lacions necessàries per a un adequat funcionament per tal d’augmentar la rendibilitat de la varietat Chardonnay, garantint de la manera més constant possible, una òptima qualitat de producció per tal d’ aconseguir un marge de seguretat més gran davant les possibles pèrdues de qualitat que es podrien originar per les condicions climàtiques adverses

Distribuição de fósforo no bulbo molhado, aplicado via fertirrigação por gotejamento com ácido fosfórico

Foram investigados a distribuição do fósforo, o pH e a umidade do solo no bulbo molhado em um Latossolo sem vegetação, após fertirrigação com ácido fosfórico, durante 21 dias. O experimento foi instalado na UNESP/Jaboticabal - SP, em blocos casualizados, com cinco repetições. Os tratamentos foram 0; 30; 60; 90 e 120 kg ha-1 de P2O5, dividindo-se as doses em quatro aplicações semanais, via fertirrigação. Após a última aplicação, foram abertas trincheiras nos bulbos molhados e coletadas amostras de solo em quadrículas de 100 cm². O ácido fosfórico provocou aumento da acidez e elevados teores de fósforo no bulbo, principalmente até 30 cm de distância lateral e até 40 cm de profundidade, em relação ao ponto de gotejamento. O aumento da dose de ácido fosfórico (90 e 120 kg ha-1 de P2O5) provocou maiores teores de fósforo e maior acidificação do solo até 30 cm de distância lateral e até 40 cm de profundidade. A distribuição do fósforo e seu efeito no pH no volume de solo molhado não seguiram a distribuição de umidade no mesmo.

Uniformidade de distribuição do potássio e do nitrogênio em sistema de irrigação por gotejamento

O uso da fertirrigação possibilita a obtenção de bons resultados, todavia é notada a necessidade de trabalhos que venham possibilitar a adoção correta da técnica. Dessa forma ,o presente trabalho buscou comparar a uniformidade de distribuição do potássio e do nitrogênio em sistema de irrigação por gotejamento. A solução de fertilizantes foi injetada durante 25 minutos, sendo recolhidas amostras de solução em diferentes momentos, durante e após ter sido finalizada a operação de injeção, tendo sido especificado o tempo de 35 minutos após o início da operação de injeção da solução de fertilizantes, como tempo-limite para a coleta da última amostra. As amostras coletadas tiveram os teores de potássio (K+) e nitrogênio (NO3- + NH4+) determinados. Com os resultados obtidos, concluiu-se que não houve variação significativa da uniformidade de distribuição de nitrogênio e de potássio no sistema de irrigação por gotejamento; maiores tempos de funcionamento de sistemas de irrigação, quando em operação de fertirrigação, possibilitam melhores uniformidades de distribuição do fertilizante, e deve-se calcular o tempo de lavagem do sistema de irrigação, pois é uma forma de melhorar a uniformidade de distribuição do fertilizante no campo.

ADJUSTED F FACTOR FOR MULTIPLE-OUTLET PIPES.

An adjusted F factor to compute pressure head loss in pipes having multiple, equally spaced outlets is derived for any given distance from the first outlet to the beginning of the pipe. The proposed factor is dependent on the number of outlets and is expressed as a function of the J. E. Christiansen's F factor. It may be useful to irrigation engineers to estimate friction in sprinkle and trickle irrigation laterals and manifolds, as well as gated pipes.

Relação entre uniformidade da produtividade e indicadores de uniformidade da irrigação em sistema de irrigação por microaspersão em citros

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desempenho de gotejadores com uso de efluente de esgoto doméstico tratado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dinâmica de entupimento de gotejadores em função da aplicação de água rica em ferro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)