Design and Performance Analysis of Low Pressure Irrigation Distribution Systems

Low-pressure pipe distribution systems forsurface irrigation provide both off- andon-farm recognized environmental benefits.However, expected benefits can only beattained when adequacy, dependability andequity of systems are high enough tosupport appropriate conditions for wateruse on the farm. An innovative methodologyfor design and analysis is proposed anddescribed, which includes the generation ofthe demand at the scale of the distributionsystem and, consequently, the generation ofthe flow regimes expected during a givenperiod of time, generally the peak month.These flow regimes are utilized for theoptimization of pipe sizes using theiterative discontinuous method for severalflow regimes. The performance analysis isdeveloped through the system simulationwith several flow regimes, which allow thecomputation of the system adequacy,dependability and equity. An application toone sector of the Sorraia irrigation systemillustrates the usefulness of themethodology proposed.     

Understanding physical clogging in drip irrigation: in situ,in-lab and numerical approaches

Dripper clogging is a major drawback of microirrigation systems that must be addressed to improve their efficiency and durability. Particle-induced clogging is first studied in situ. The experiments consist in observing in real conditions the behavior of a series of drippers fitted on an agricultural plot in the south of France. The plot is supplied from a canal with Durance River water. The latter is loaded with sediments that gradually clog drippers and filters. Water analysis reveal that physicochemical clogging prevails over biological clogging. This characterization helps in setting in-lab experiment protocol. Indeed, besides field observation of clogging, laboratory analyses of both the irrigation water and the clogging material are performed with reactive and inert clay: smectite and an illite–calcite mix. A surprising tendency is observed: Salt concentration in smectite seeded water decreases the clogging, whereas it increases agglomerate size. Computational fluid dynamic simulations are carried out to investigate the impact of particles on flow behavior. Results demonstrate that clay particles interacting with the flow govern the complex structure of the fluid velocity fields inside the dripper labyrinth channel.     

The relationship between seed weight, germination and biochemical reserves of maritime pine (Pinus pinaster Ait.) in Morocco

Seed germination and biochemical reserves of maritime pine (Pinus pinaster Ait.) were studied with the aim of providing germination information for reforestation and conservation programs. Ten natural populations were used to assess variation in seed weight, germination characteristics and biochemical reserves and to examine the relationship between these characteristics. The analysis of variance showed highly significant population effects for seed weight, germination characteristics and protein content in both seeds and the female gametophyte. The mobilization of protein content in female gametophyte during seed germination differed more among populations than sugar content, suggesting that protein content was more sensitive to environment effects than sugar content. A strong positive correlation between germination capacity and the protein content in both seeds and female gametophyte indicated that the best populations in term of germination capacity may also be the richest in protein content. Seeds that were heavier and had a lower speed of protein content mobilization in the female gametophyte appeared to be better adapted to drought conditions. The results also suggested that as much as possible of the potentially valuable genetic variation among populations of this species should be preserved for reforestation and conservation purposes.