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- Lettuce yield response to salinity of sprinkle irrigation waterPublication . Beltrão, José; Trindade, D.; Correia, P. J.The objective of this work is to study the effect of saline water on the yield of lettuce (Lactuca sativa L., var. longifolia Lam., cv. Nevada), under an experimental design known as double sprinkler line source (DLS), in two different soil types. A saline gradient was created, shown by an electrical conductivity from 1 up to 8 dS/m, and a precise distribution of the salt with a minimal experimental area was obtained. Experiments were carried out in the Campus of Gambelas, University of Algarve, Fare, South Portugal. Lettuce yields were expressed in ton/ha and in fresh weight per plant. It is concluded the main several aspects: 1 - A steep yield reduction from 1 up to 2 dS/m; 2 - A slow yield reduction from 2 up to 5 dS/m; 3 - From 5 up to 8 dS/m yield is very low and near constant. Regression curves had r(2) values not lower than 0.80.
- Combined effects of potassium and wastewater application on the yield and quality of Bermuda grass (Cynodon dactylon) in the Mediterranean regionsPublication . Beltrão, José; Santos, R.; Correia, P. J.The reuse of treated wastewater is considered as an alternative disposable to potable water in the mediterranean agriculture and landscape, namely in golf courses. Bermuda grass (Cynodon dactylon, Peers) is used very often on the fairways, roughs and tees of golf courses of the Mediterranean Basin due to its tolerance to drought, salinity, high temperatures and damages. The objective of this work is to study the response of this cultivar to the combined effects of municipal wastewater and two levels of potassium fertilization, during Spring and Summer. The experimental design known as sprinkle point source was used to simulate the various levels of wastewater application, expressed by the crop coefficient kc. This procedure is characterized by the assumption that a point creates a linear irrigation gradient from the water point source, producing a gradual change in water application, and a high degree of irrigation uniformity must be obtained in parallel isohyets. Chemical analysis of wastewater irrigation water was monitored through all the experimental period (from April to September). Climatic data was also recorded. Yield (aboveground biomass) and the good visual appearance (GVA) of the lawn were assessed in two sampling dates, May and July. Municipal wastewater can be used to irrigate Bermuda grass, without an apparent decrease on grass quality. As concluding remarks, it may be seen that the irrigation water amount is the most pronounced limiting production factor of bermuda grass (Cynodon dactilon, Peers), when compared with potassium fertilization, but it is possible that there is a positive interaction between water and irrigation. This response is modulated by evaporative air conditions since lower yields were obtained in summer. On the other hand, if the potassium fertilization is increased, two situations may occur: 1) with high amounts of water application, leaching problems may occur, mainly on sandy soils, and production may decrease; 2) if potassium fertilization increases, and irrigation water decreases, yield decreases due to the increase of salinity (potassium fertilizers are salts), mainly on salt affected soils.