Comparison between land suitability and actual crop distribution in an irrigation district of the Ebro valley (Spain)

Abstract

The present research aims to obtain a better insight into the agreement between land evaluation results and actual crop spatial distribution by comparing biophysical land suitability with different crop frequency parameters and with crop rotations derived from multi-year crop maps. The research was carried out in the Flumen district (33,000 ha), which is located in the Ebro Valley (northeast Spain). Land evaluation was based on a 1:100,000 soil survey according to the FAO framework for the main crops in the study area (alfalfa, winter cereals, maize, rice and sunflower). Three crop frequency maps and a crop rotation map, derived from a time-series of Landsat TM and ETM+ images of the period 1993-2000 were used for comparison with land suitability maps. The relationships between the two types of variables were analyzed by means of statistical tests (Pearson chi-square (χ 2 ), Cramer´s V, Gamma and Somers´ D). The results show the existence of a significant (P=0.001) relationship between crops' location and land suitability, except for opportunist crops as sunflower, which is very much influenced by subsidies in the study period. The alfalfa-based rotations show the highest distribution percentages (52%) on the land most suitable for agriculture in the area. The present multitemporal analysis approach offers a more realistic insight than the comparison between a land evaluation map and static year crop map in assessing the degree of agreement of land evaluation recommendations with crops actually cultivated by farmers.Additional key words: biophysical land suitability, crop rotation, land evaluation. ResumenComparación entre la aptitud de las tierras y distribución real de los cultivos en un distrito de riego del valle del Ebro (España)El objetivo de la presente investigación fue analizar la correspondencia entre los resultados de una evaluación de tierras con la distribución real de los cultivos. Para ello la aptitud biofísica de las tierras se comparó con diferentes tipologías de frecuencia de ocurrencia de los cultivos y rotaciones derivadas de mapas de cultivos multitemporales. La investigación fue llevada a cabo en el distrito de riego de Flumen (33.000 ha), localizado en el valle del Ebro (NE España). La evaluación de tierras se basó en una cartografía de suelos 1:100.000, según el esquema FAO, para los principales cultivos presentes en el área de estudio (alfalfa, cereales de invierno, maíz, arroz y girasol). Se utilizaron tres mapas de frecuencia de cultivos y un mapa de rotaciones, derivado de una serie temporal de imágenes Landsat TM y ETM+ del periodo 1993-2000, y se compararon con los mapas de aptitud de tierras para los diferentes cultivos. Se analizó estadísticamente (Pearson χ 2 , Cramer V, Gamma y Somers D) la relación entre los dos tipos de variables. Los resultados muestran la existencia de una relación significativa (P=0,001) entre la localización de los cultivos y la idoneidad de las tierras, excepto de cultivos oportunistas como el girasol, muy influenciado por las subvenciones en el p...

Assessment of the FAO traditional land evaluation methods, A case study: Iranian Land Classification method

“…Farmers therefore prefer to cultivate this crop because it provides higher incomes. A similar result was reported by Mart ınez-Casasnovas et al (2008) for opportunist crops, such as sunflower in Spain, which was very much influenced by European Union subsidies during the study period.…”

“…A similar result was reported by Martínez‐Casasnovas et al . () for opportunist crops, such as sunflower in Spain, which was very much influenced by European Union subsidies during the study period.…”

“…Martínez‐Casasnovas et al . () compared land suitability and actual crop distribution in an irrigation district in Spain's Ebro valley. Their results showed the existence of a significant relationship between crop location and land suitability over time.…”

“…They also suggested that, as the FAO method correctly predicts mean regional farm yields, it could also be useful for land-use planning. Mart ınez-Casasnovas et al (2008) compared land suitability and actual crop distribution in an irrigation district in Spain's Ebro valley. Their results showed the existence of a significant relationship between crop location and land suitability over time.…”

Feature Selection Parallel Technique for Remotely Sensed Imagery Classification

“…If its value is large, then there is a tendency for particular categories of the first variable to be associated with particular categories of the second variable. It has been suggested in practice that a Cramer's V of 0.1 provides a good minimum threshold for suggesting there is a substantive relationship between two variables [18].…”