Browsing by Author "Gonçalves, J.M."
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- Effects of Sand Addition to Heavy Saline-Alkali Soil on the Infiltration and Salt Leaching in Hetao Irrigation District, ChinaPublication . Miao, Q.; Zhou, L.; Gonçalves, J.M.; Duarte, I.M.; Li, R.; Shi, H.Soil salinity is a matter of great economic and environmental implications. In Hetao Irrigation District, soil salinity limits crop productivity affecting about 69% of its total cultivated land due to natural soil salinisation and salt accumulation caused by irrigation. The goal of this study is to contribute to the alleviation of this problem through the technique of adding wind-sand to the top layer of heavy saline-alkali soil, and to evaluate and analyse their effects on the infiltration and salt leaching. The experiment was carried out on a laboratory scale. Clayey soil with 21 g/kg of salts collected at the Ulat Front Banner site was used. Wind-sand was added to the top 30 cm layer of this soil. The infiltration tests were carried out in plastic columns with 9 cm diameter and 45 cm high, loaded with a soil and wind-sand mixture (from 2% to 30% ratio), supplied by a constant hydraulic head. Soil water samples were collected for 15 days for quantification of the soil salt leaching. A significant increase of the infiltration rate was observed in the first infiltration hour, rising from 1 to 9 mm/h, in response to the addition of 8% and 30% of sandy particles, respectively. The effects of wind-sand in salt leaching were relevant in the top 20 cm layer. After 7 days of infiltration there was a decrease in the salt content in soils with 4%, 8%, and 30% of sand particles added, of 35%, 55%, and 95%, respectively, in relation to the control. In conclusion, the practice of adding sandy particles to the topsoil is a soil melioration method that allows a positive impact on soil infiltration and salt leaching. An addition of 8% of sand seems to be a good choice, as it favours an increase in salt leaching of about 55% after 7 days. These results are encouraging and appeal to field studies to assess the impact on a field-scale system, and the effects of this soil melioration on irrigation, drainage, and agronomic aspects
- MIRRIG: a decision support system for design and evaluation of microirrigation systemsPublication . Pedras, C.M.G.; Pereira, L.S.; Gonçalves, J.M.The decision support system (DSS) MIRRIG has been developed to support the design of microirrigation systems and to advise farmers as a result of field evaluations. It is written in Visual Basic 6.0, runs in a Windows environment, and uses a database with information on emitters and pipes available in the market, as well as on crops, soils and the systems under design. MIRRIG is composed by design and simulation models and a multicriteria analysis model that ranks alternative design solutions based upon an integration of technical, economic and environmental criteria. User friendly windows are adopted for handling the databases and to manage the sub-models. The model allows creating and comparing a set of design alternatives relative to the pipe system and the emitters, either drip or microsprinkling emitters. For each alternative, the pipe system is sized and the irrigation system is simulated to produce performance, environmental and economic indicators. These include uniformity of water application, potential for contamination with agrochemicals due to water percolation, and installation and operation costs. Those indicators are used as attributes of the selected criteria. All alternatives are then compared and ranked through multicriteria analysis where the weights giving the relative importance of the adopted criteria are defined by the user. These procedures allow selecting the best design alternative and solving the complexities involved in the design of microirrigation systems. The model is available from the website www://ceer.isa.utl.pt/cms