Effect of Harvesting Time on Quantitative and Qualitative Characteristics of Artichoke (Cynara scolymus L.) Forage

Artichoke (Cynara scolymus L.) (Asteraceae) is an herbaceous perennial plant of Mediterranean origin, North Africa, Canary Isles and Southern Europe. Nowadays, artichoke is cultivated in many parts of the world, such as the United States, mainly in California, in South America (Argentina, Chile, Peru), North Africa, Near East (Turkey and Iran) and China. Artichoke has a medicinal property. It also can be used as a green fodder or silage for livestock feeding. In addition to dry matter yield, forage quality has also a great importance in the production of forage crops. The quality of forage species varies in different places and times. In general, the factors affecting forage quality changes can be described as environmental factors (light, temperature, soil characteristics, precipitation, altitude, wind, and humidity), growth stage and harvest time, plant species, photosynthetic pathway (C3, C4, and CAM) and management factors. Therefore, the purpose of the present study was to investigate the forage quality of artichoke in different growth stages for livestock feeding. In order to evaluate the yield and forage quality of Artichoke (Cynara scolymus L.) at three stages of growth, an experiment was conducted using a randomized complete blocks design (RCBD) with three replications at the Research Station of Isfahan Agricultural and Natural Resources. The treatments were harvested at three growth stages (vegetative, flowering and early seeding). Seeds were sown on 26 April 2014. Chemical fertilizer (urea) applied based on soil analysis results. The first half of the nitrogen fertilizer was utilized as strip takes under seed before sowing and the rest at 7-8 leaf stage of the crop on 26 May 2014. The cultural practices of Artichoke were not conducted in the second year because it is a perennial plant. According to the soil test, half of the nitrogen fertilizer in the first year of experiment applied in the second year. The plants were harvested at vegetative, flowering and the beginning of seed ripening stages in the second year. After harvesting, samples were dried normal air circulation until to reach constant dry weight. Dry matter yield and forage quality indices as crude protein, organic matter digestibility, total ash, neutral detergent fiber, acid detergent fiber, Na and K contents were measured. Analysis of variance was done using SPSS software and comparison of the means was conducted using by Duncan at 5% level. The results of this experiment showed significant differences for all traits among the phenological stages (p<0.05). For dry matter, the lower and higher values of 5.8 and 8.75t ha-1 were obtained, in vegetative and early seeding stages, respectively. Forage quality decreased with increasing plant age and it was the highest in the vegetative stage compared to other stages. Crude protein, organic matter digestibility, total ash, Na and K content in the vegetative stage were more amount than other stages. Neutral detergent fiber and acid detergent fiber tended to increase while, crude protein, organic matter digestibility, total ash, Na and K content tended to decrease with advanced plant maturity. Artichoke plant has young and large leaves at vegetative rosette stage. The leaf to stem ratio decreased with advanced plant maturity and it is higher at flowering stage than the early seeding stage. Forage quality in the vegetative stage was more than of both flowering and the early seeding stages. Growth stage and harvesting time were the important factors that affecting forage yield and quality of Artichoke. For age quality decreased with the progress in plant growth, while dry matter yield increased. Generally, the flowering stage is the best time for harvesting artichoke forage.