Crop yield and quality parameters of four annual fibre crops (hemp, kenaf, maize and sorghum) in the North of Italy

Abstract

Four fibre crops (hemp, kenaf, maize and sorghum) considered amongst the most suitable for the conditions of Northern Italy were compared in 1995 and 1997, over two irrigation regimes (rainfed conditions and restoration of 100% ETp) and in two locations (Bologna and Milano). Three harvests were carried out on each crop at different development stages. At each harvest time data on yield and yield components were collected. Sub-samples of stems of each crop and at each harvest time were analysed following the Van Soest method. On average, fibre sorghum proved to be the higher yielding crop. It produced 26.2 Mg ha −1 of total dry matter of which 18.1 Mg ha −1 was partitioned to the stems. Fibre maize produced more total dry matter than kenaf (19.0 Mg–15.7 Mg ha −1) but dry matter accumulated to stems was higher in kenaf (10.8 and 13.4 Mg ha −1). On average, fibre hemp yielded 14.0 Mg ha −1 of total dry matter and 10.9 Mg ha −1 of stems. This result was highly affected by the low hemp production in Bologna in 1995, where unfavourable conditions, in the first phases of cultivation, resulted in a stunted establishment of the crop (18.7 Mg ha −1 of total dry matter in Milano and only 8.3 Mg ha −1 of total dry matter in Bologna). On all crops, irrigation produced a slight increase in total biomass (7%) and in stem dry matter (9%) compared to the rainfed condition. In both locations, yield increase due to irrigation was larger in maize and kenaf, than in hemp while, in 1995, it caused a severe lodging on sorghum. The four species proved to be different for growth rates, patterns of development and particularly for cellulose, hemicellulose and lignin content of stems. Cellulose content varied between 56–66% of stem dry matter in hemp, 46–57% in kenaf, 35–45% in maize and 39–47% in sorghum. As harvest time was delayed, cellulose content tended to increase for hemp and kenaf while it decrease for sorghum and maize. Hemicellulose content of hemp and kenaf stems varied between 16–19%, while it varied between 26–29% in sorghum and maize. Hemicellulose content decreased with irrigation and with delay in harvest time. Lignin content in hemp stem ranged between 8 and 13%, it was 6.9% in kenaf and maize, and ca 8% in sorghum.