The influence of rainfall and tillage on wheat yield parameters and weed population in monoculture versus rotation...

Extreme climate events (ECEs) of drought are becoming common in Mediterranean areas and farmers need adapt agricultural practices to achieve sustainability. This field study took place in to gain insight into the effects of seasonal rainfall, tillage and crop systems on wheat yield and weed parameters. Conventional (CT), minimum (MT) and no-tillage (NT) systems in wheat monoculture and rotation cropping systems were tested during 3 years of study (2014-2015, 2015-2016 and 2016-2017). Growing Season Rainfall (GSR) was the most influential factor on yield parameters and weed population. In 2016-2017, categorized as an extreme climate event by drought, the GSR accounted for 43.4% of the historical average. This year, the wheat yield (373 kg ha^-1) and harvest index (0.18) were the lowest. In 2015-2016, scarcer autumn rainfall (44 mm) affected the weed germination period, reducing the density (17 plants m^-2) and diversity of weed species (3 species m^-2) while yield was favoured by high winter and spring rainfall (247 mm). Our study revealed that tillage effects was not significant on wheat yield, but NT systems consistently showed higher weed density and diversity than CT and MT despite the irregular GSR during this study. The rotation system presented higher values of wheat grain yield (781 kg/ha) and dry straw biomass (1803 kg/ha) but also weed biomass (48.54 g m^-2) compared to monoculture (27.50 g m^-2). NT and rotation combined increased the weed community although did not reduce the wheat yield compare to conventional systems even with an ECE of drought.