Thesis Doctoral. Antonio Giménez Morera 

Use of agrotextiles. Analysis of viability and model of the effectiveness.

Abstract.

Ten representative research sites were selected in Eastern Spain to assess soil erosion rates and processes in new citrus orchards on sloping-soils. The experimental plots were located representatives sites on limestone, in areas with 498 to 715 mm y-1 mean annual rainfall, north-facing slopes, herbicide treated, and new (less than 3 years old) plantations. Ten rainfall simulation experiments (1 hour at 55 mm h-1 on 0.25 m2 plots) were carried out at each of the 10 selected study sites to determine the integral soil erosion and runoff rates. The 100 rainfall simulation tests (10 x 10 m) showed that pounding and runoff occurred in all the plots, and quickly: 121 and 195 seconds respectively, following rainfall initiation. Runoff discharge was one third of the rainfall, and sediment concentration reached 10.4 g l-1. The soil erosion rates were 2.4 Mg ha-1 h-1 under 5-year return period rainfall thunderstorms. These are among the highest soil erosion rates measured in the Western Mediterranean basin, similar to badlands, mine spoil and road embankment land surfaces. The positive relationship between runoff discharge and sediment concentration (r2 = 0.83) shows that the sediment availability is very high. Soil erosion rates on new citrus orchards growing on sloped-soils are neither tolerable nor sustainable.
In spite of its environmental and economic benefits the use of geotextiles little is extended in Spain by lack of information between the users. The geotextiles, are adapted in zones of low rainfall when improving the hydric retention of grounds and to avoid the direct evaporation and the evaporate of the plants. In spite of being evaluated positively its utility in horticulture and fruit growing its use has not extended. The crisis in which the textile industry is surrounded, causes that new products look for that allow the diversification of the production. The geotextiles are one of them. In addition the geotextiles improve the management of the agricultural operations and reduce the environmental impact of agriculture. It is avoided the use of herbicides and fitosanitarios that alter the agricultural ecosystems. In this work a revision of the geotextiles available in the market is made and examples of their use in the field are exposed.
Los agricultural grounds is those that contribute with greater losses of ground and waters. The use of herbicides is the extended handling more in the Valencia agriculture of dry land. The search of more sustainable alternatives has done than the use of geotextiles applied to agriculture (agrogeotextiles) more and more is extended. This work presents/displays the results of the measurements taken in eight parcels of 1, 2, twin 4 and 16 m2 with herbicida treatment and agrogeotextiles in the “Experimental Station for the Study of the Erosion of Soil of the Teularet-Mountain range of Enguera” in which it has been verified that the use of herbicides favors the loss of ground. The agrogeotextiles produce greater run-offs during the year of study, but the one is the treatment with herbicida that contributes with losses of ground elevated when being the naked fields by the vegetation absence. In particular, the sediment concentration of the poured one coming from the parcels dealt with herbicida reached values 173 times higher than those of the deal with geotextil, and the rate of final erosion was of 26 times greater in the herbicida. The agrogeotextil only presents/displays the problem of a greater run-off which had to the hidrofobic of the cotton weave, a problem that must be studied to be corrected in the geotextiles for his in agriculture.
High soil erosion risk of Mediterranean cultivated soils is due to steep slopes, high rainfall intensities and low vegetation cover. Traditional land management as ploughing and Herbicides give rise to high soil erosion rates. This paper reports on the use of a cotton Geotextil to control soil and water losses on agricultural land under Mediterranean climatic conditions. Eight paired plots (1, 2, 4 and 16 m2) were studied during one-year period under natural rainfall. Forty rainfall simulations under wet and dry climatic conditions, and water drop penetration time (WDPT) tests, were carried out in order to analyze the effect of a Geotextil on soil and water losses on a typical rainfed orchard in Eastern Spain. Results showed that an 8 mm thick cotton Geotextil reduced soil loss to negligible values (from 14 to 0.1 Mg ha-1 y-1) due to the low sediment concentration as Geotextil covered 100 % of the soil. However, infiltration rates decreased and runoff increased due to the hydrophobic response of the cotton material. The runoff discharge increased from 8 to 16 % for the 2004 period under natural rainfall and from 27 to 87 % under simulated rainfall when summer dry conditions were reached. The cotton Geotextil reduced local soil losses at plot-scale, but increased runoff. 
The reduction of the circulating volume of Riu dels Sants, has been a constant from 1970. This reduction of volume has had to a great extent to the uncontrolled increase of the extractive demand. The not control of perforations, changes of cultures and systems of irrigation has done that during most of the year, the channel is dry in its totality. At the moment, an economic yield looks for only and exclusively the water extraction, and serves the channel as laughs like mere spectator of the passage of the water by him. This situation has caused that makes worse the conditions of contamination to which the channel of the river is exposed and year is degraded after year. This makes the search necessary of projects that help to the regeneration of the channel and the maintenance of an ecological minimum volume. This work points some solutions in the crossroads of a river without volume.
The ecological handling of the long waits of orange tree and mandarinos presents/displays problems for the management of the bad grass. The handling with geotextil and manual traditional weeding is compared from an economic, environmental and agronomic point of view. During 17 months a pursuit of the 200 long waits (10 of March of 2006 to 10 August of 2007) with the purpose of knowing the number of marras has been made, circumference of the trunk, diameter of glass and height of the tree to determine the viability of both handlings. Although the handling with geotextil is slightly economic, also causes a greater number of marras. To the reasons of these differences and the complex handling of the geotextil are discussed when it settles in parcels with located irrigation.
Although the economic viability in the use of geotextiles in citricultura already has been studied (A.Giménez-Morera 2008) contemplating the repercussions of its use, is necessary the use of other methodologies that allow the hierarchical structuring us of the different geotextiles more used comparatively with the working to help in the decision making on the part of the user. We used in this work a productivity analysis/efficiency that will lead to us to complete or incompletes mathematical models that will look for rankings. Units of decision have been taken previously selected that come from a study of the basic characteristics that cause that the user makes the decision to use or not to use a geotextil. We will obtain a complete ranking of alternatives by means of the Single method Price Model.  The hierarchical structuring of the geotextiles and the working will allow to select those us that are more efficient and it will distinguish them of that they follow it.