Effects of different soil water tensions on rapeseed crops (Brassica napus L.)

Abstract

Correct irrigation management aims to determine the right amount of water at the right time.  Also, it is one of the available tools to reduce energy and water costs, enabling maximum crop production.  Considering these aspects, a study was conducted to determine the effects of different soil water tensions on rapeseed crop.  For this purpose, an experiment was carried out in Brazil, at the department of Agricultural Engineering at the Federal University of Lavras, from April to October 2008.  The experimental design was completely randomised, with four treatments of different soil water tensions (20, 40, 80 and 120 kPa) and four replicates amounting to 16 experimental plots.  Crop vegetative, productive parameters and qualitative grain parameters were evaluated.  According to the variance analysis, different soil water tensions affected the number of pods, the number of branches, dry matter of the vegetative part, dry matter of pods, total dry matter and yield, by F test at 5% probability.  While, the physical quality of the grains, the weight of 1000 grains and specific matter were not affected by treatments.  Water retained at 25 cm of depth and at 20 kPa tension proved to be a good indicator of the correct amount of water to start irrigation of rapeseed crop, as the highest grain yield was achieved with this treatment.  Grain yield sensitivity to water deficit, represented by yield response factor ky, was lower than one, indicating that supplementary irrigation caused proportionally smaller yield decreases when compared to the reduction in applied water.

Keywords: water irrigation, rapeseed, yield, water tension on soil