Response of spring wheat genotypes to organic farming systems in low-fertility soil

Low-fertility soil is considered a major challenge for growing wheat (Triticum aestivum) in organic systems. The objective of this study was to identify spring wheat genotype(s) adapted to growing in organic systems with low-fertility soil compared with conventional systems in the central region of Saudi Arabia. Organic and conventional trials were established during the 2010, 2011 and 2012 growing seasons in the arid environment of central region of Saudi Arabia. Both trails were seeded in a sandy loam soil. Eight bread wheat genotypes were evaluated for the following parameters: grain and straw yields, grain-filling rate (GFR), days to heading (DTH), days to maturity (DTM), number of kernels per spike and 1000-kernel weight. The experiment was a randomized complete block design (RCBD) with four replications. The findings showed that there were significant differences in grain and straw yields between the two systems and among genotypes. The Egyptian genotypes 'Sids 12' and Early-line produced the highest grain yields (7.8 tons ha-1) in the conventional system, whereas in the organic system, Yocora Rojo (control genotype) and Early-line produced the highest yields (5.8 and 5.9 tons ha-1, respectively). Grain and straw yields were higher in 2011 and 2012 growing seasons compared to 2010. Early-line and ICARDA genotypes (IC8 and IC17) had the highest grain-filling rate, whereas the Australian genotypes (P5 and P3) and the local genotype 'Sama' had the lowest grain-filling rate. The genotype Early-line had the shortest time to heading and maturity in both systems. Therefore, Early-line and Yocora Rojo are promising bread wheat genotypes for organic production systems in low-fertility soil.