Consumi idrici ed esigenze in azoto della canapa da cellulosa

The cultivation of paper making hemp has raised to new prospects depending on the world crisis of paper, so that in some Country, as France, such cultivation has reached a spreading of about 5.000 hectares, in connection with the new techniques which allow the complete mechanization too. In 1972 and 1973 the Institute of Agronomy of the University of Sassari has studied some aspects of the cultural technique of paper making hemp. The sown, using a hybrid originated from France (R1D7,F36, N), with 60 kg/ha of seed, has been carried out on 8th april in 1972 and on 20th april in 1973. Two water volumes (400 and 800 mc/ha), 3 irrigated intervals (8-12-16 days), 4 doses of nitrogen (0-75-150-225 kg/ha of N) and three times of harvest (3 July, 19 July, 5-6 August) have been compared. The more suitable harvesting time seems to be the second one (19 July) either in 1972 or in 1973. In the limit of this period yields of stalk at 15% of moisture, in the mean of nitrogen treatments, have fluctuated in 1972 from 131,5 q/ha in the thesis with interval of 12 days and unit water volume of 800 mc/ha to II8.3 q/ha with interval of 16 days and unit water volumes of 400 mc/ha; in 1973 yields at the second harvest time in the mean of the N thesis, have fluctuated from 155,3 q/ha in the thesis with interval of 8 days and uni t water volumes of 800 mc/ha to 123,6 q/ha in the thesis with interval of 16 days and unit water volume of 400 mc/ha. In both years the cultivation has reacted positively to N supplies. In the second harvesting time and in the mean of the irrigated thesis, in 1972, we have become from 161,8 q/ha of stalk in the thesis with 225 kg/ha of N to 72,6 q/ha of the test not fertilized; in 1973 differences turned out to be less marked coming from 151,4 q/ha of the thesis 150 kg/ha of N to II 7,3 q/ha of the test. As already told, the time more suitable for the stalks'cut falls in the 2ª decad of July. Consequently the cultural cycle is come out of about 90-100 days. Such a speed in the growth of hemp under Sardinian environment seems to be interesting in relation with the possibility of limiting water consumptions and with the introduction of hemp in intensive cultural arrangement.