Optimum use of the irrigational water in a wide-spaced irrigation technology

Milena Moteva, Georgi Kostadinov

Abstract: A six-year field experiment with wide-spaced irrigation of corn was conducted in Sofia region. Three irrigation depths, based on 80%, 75% and 70% of field capacity, and their 50% and 66% reductions, distributed on every furrow, every-other fixed furrow and every-third fixed furrow were tested. The soil was Chromic Luvisols (LVch). Multiple regression analysis was developed to establish the combined effect of three factors: irrigation depth, number of applications and space between the irrigated furrows on the parameters: relative additional yield (RAdY) and relative irrigation water use efficiency (RIWUE). Statistica, Mathcad and Excel software were used for data processing and illustration. A generalized parameter of optimization: an average utility function (AUF) was developed in order to establish the conditions for obtaining maximum RAdY at maximum relative irrigation water use efficiency (RIWUE). It was found that RAdYmax can be obtained when distributing in every-other-fixed-furrow (EOFF) the maximum irrigation depth through a maximum number of applications. The number of applications has the biggest effect on the additional yield, while the irrigation depth has almost half of that effect. RIWUEmax is obtained when maximum irrigation depth is distributed in ETFF through a maximum number of applications. The spatial pattern of water distribution has the biggest effect on RIWUE. The number of applications has the least effect. RAdYmax and RIWUEmax are simultaneously obtained through the EOFF technology. The irrigation depth and the number of applications should be maximal. When EOFF is applied, around 10% of the irrigation depth can be saved, while RAdY and RIWUE are nearly maximal.

Keywords: corn; irrigation water use efficiency; multiple regression analysis; optimization; wide-spaced irrigation; yield

Date published: 2019-02-20