A wheat-fallow rotation in northeastern Spain: water balance-yield considerations

KJ McAneney*, JL Arrúe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


A 35-yr time series of dryland wheat yields and corresponding monthly rainfall data from the Los Monegros/La Ribera del Ebro-Zaragoza area in Central Aragon have been examined with a view to determining the efficacy of the wheat-fallow rotation. Grain yields are low (average of 1 050 kg/ha) and highly dependent on seasonal (October-May) rainfall. In some years no harvestable yield is possible. The contribution of stored water during the fallow period appears minor either because of a low soil water-holding capacity, poor weed control, or because of the nature of the rainfall distribution. The latter is characterised by the absence of any well-defined rainy season and in any month there exists a strong probability of having either no or an extremely low amount of rain (< 10 mm). The Tanner and Sinclair (1983) result suggesting that transpiration efficiency is a stable characteristic for a cropping system is used to calculate transpiration from grain yields. Evaporative losses are then calculated by difference with ihe seasonal rainfall on the accumption that drainage and surface runoff were negligible. On average, 70% of the average seasonal rainfall is estimated to be lost either as evaporation or transpiration by weeds. The water use efficiency of grain production approached the average potential (16.7 kg ha-1 per mm water transpired) in only 3 out of 35 yr. In other years, evaporative losses accounted for a greater proportion of evapotranspiration, reflecting reductions in growth due to factors other than water such as poor plant nutrition, pests and diseases, etc.

Original languageEnglish
Pages (from-to)481-490
Number of pages10
Issue number6
Publication statusPublished - 1993
Externally publishedYes


  • dry matter production
  • dryland wheat
  • fallow period
  • grain yield
  • semi-arid region
  • water budget
  • water-use efficiency


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