Bearing in mind that more than 50% of the land used for agriculture in Mexico is under semiarid and arid conditions, water availability and nutrition are among the main handicaps for crops to produce, particularly if they are fruit species. From the total area cultivated with apple, 36% is grown under rainfed conditions with a 4.2 t ha(-1) yield. Therefore, technology for improving nutrition with a more efficient use of available water is now being considered, in order to increase fruit yield and quality. This could lead to obtaining higher profits, and to being able to access more specialized systems in addition to ensuring a sustainable development. Growth, production, N, P, K, Ca, Mg, Mn, Cu, Fe, and Zn foliar concentration were determined in 'Agua Nueva II' apple trees, a low chilling mutant of 'Golden Delicious', grown in semiarid condition. Mulching (manure, grass residues, and bare soil as control), irrigation (flood irrigation and rainfall as control), and foliar fertilization (2.0 kg free biuret urea + 2.0 L Bayfolan + 200 mL surfactant ha(-1) sprayed twice a month, and control) treatments were studied. A split plot design with three randomized blocks was used for statistical analysis. Before applying the treatments in August 1997, the nutritional condition of the apple plants was established; Cu and Zn foliar concentration were deficient. Results in 1998 showed a general plant growth, production and nutritional condition improvement with some of the treatments. Flood irrigation significantly affected plant growth, as N, P, K, and Mn concentrations in leaves. Manure mulching also affected significantly plant growth and K concentration and caused the highest yields per tree. Zn concentration reached sufficiency levels, while Cu remained deficient.

En las zonas declaradas vulnerables a la contaminación de nitratos en Navarra, uno de los cultivos de mayor interés por la superficie que ocupa y por sus necesidades nitrogenadas es el maíz. Se ha realizado un estudio en la zona sur de Navarra (Tudela) sobre el cultivo de maíz para determinar el efecto del riego por aspersión e inundación y de tres dosis de nitrógeno sobre el proceso de lixiviación y la eficiencia del agua de riego y del N aplicado como fertilizante. El estudio se ha realizado durante tres años. Los resultados mostraron de forma general, un menor rendimiento del maíz y una peor eficiencia del uso del agua y del N fertilizante cuando se utiliza riego por inundación que cuando se utiliza riego por aspersión independientemente de las dosis de nitrógeno estudiadas. Por otra parte, la lixiviación de nitrato se incrementó al incrementar la dosis de nitrógeno. Respecto al riego, con riego por inundación la lixiviación en principio es mayor que por aspersión debido al mayor drenaje que genera, pero en aspersión queda un nitrógeno residual que se acumula en el suelo que es susceptible de ser lavado en periodos intercultivo o cuando el cultivo no es capaz de utilizarlo.

Accurate estimation of irrigation return flow plays an important role in the effective management of groundwater, especially in arid and semiarid irrigation regions. However, there is a lack of sufficient research to clarify hydrological process dynamics associated with irrigation return flow. In this study, first, a two-dimensional/three-dimensional model, HYDRUS-2D/3D, was adopted to analyze two different irrigation types in the Delingha Depression, which is located at the northeastern margin of the Qaidam Basin, China. Then, a 3D saturated flow model was established. This study determined the effect of agricultural water application on the dynamics of irrigation return flow. A large difference in the irrigation return-flow coefficient (IRFC) was seen during the growing season; an IRFC of 0.3 was obtained using flood irrigation, whereas ditch irrigation resulted in an IRFC of only 0.1. The lag time of recharge was approximately 150 days. It was necessary to consider the lag time for the 3D numerical model to obtain satisfactory results. Flood irrigation led to a groundwater recharge rate of 90 mm/year. These results indicate that the lag time should be considered when groundwater recharge is estimated or modeled.