Partition of rainfall variation effect on crop productivity into amount and distribution effects

Independent and previously-researcher at INRA Maroc, Morocco

^* Corresponding author: jlibene.mohammed@gmail.com

Abstract

Rainfall is the most influential factor of rainfed agricultural production in semi-arid Mediterranean and Sub-Saharan environments. While effects of rainfall amount and distribution are confounded, their partition will help developing strategies to manage green water in these environments. A series of 39 years of country average cereal yield and rainfall data was used (1981-2019). Cumulated rainfall over months of November, Rainfall of the month of January, February and March of Central location of Marchouch (33.5613° N, 6.6919° W) taken as a representative of agricultural land, were used because of high correlations with yield. Regression of cereal yields on rainfall showed scattered points below a top frontier line representing highest water productivity (yield/rainfall), accounting for effect of amount independent from distribution. Regression of all 39 yields on rainfall accounts for both confounded effects of amount and distribution. Difference indicates effectofdistribution of rainfall. Cumulated rainfall over the 4 months, varied from 64.20 mm to 447 mm with an average of 219 mm. Yields ranged from 3.59 q/ha to 22.88 q/ha with an average of 12.29 q/ha. Top water productivity indicating effect of amount was 3.98 kg/mm. Distribution of rainfall reduced actual yields by 13% to50% depending on season and cereal crop. The model can be adapted to rainfed crops in semiarid environments.