Introduction and management of vetch/barley forage mixtures in the rainfedareas of Pakistan - 3. Residual effects on following cereal crops

The residual erects of winter-sown forage mixtures grown in the northern ra infed parts of Punjab province and south-eastern North West Frontier Provin ce in Pakistan were examined. Studies were carried out during 1994-97 prima rily at the National Agricultural Research Centre (NARC), Islamabad, which has an annual rainfall of around 1000 mm and, secondarily, at a much drier site at the Arid Zone Research Centre (AZRC) at Quetta. Common vetch (V), b arley (B), and their mixtures at seed ratios of V75B25, V50B50, and V25B75 were sown and 3 harvest time treatments (pre-flowering, full flowering, and maturity) were imposed. Sorghum, and then wheat, were grown as succeeding crops to monitor the residual erects of the introduction and management of legume forage mixtures. Significant residual erects on the dry matter produ ction and nitrogen (N) content of sorghum (P < 0.01) were observed at both NARC and AZRC following different vetch/barley seed ratio treatments. Sorgh um dry matter yield after pure vetch and after the mixture ratio treatment of V75B25 was higher (4.5 t/ha) than after other mixtures and it was lowest after sole barley (2.5 t/ha). The N taken up by the sorghum after pure vet ch amounted to 56 kg/ha and after pure barley was 25 kg/ha. Nitrogen yield from the sorghum decreased with increasing amount of barley in the mixture. There were no apparent erects of the previous harvest time treatments impo sed on the forages. Differences in dry matter production and N content in w heat following sorghum at NARC were just detectable after different vetch/b arley seed ratios. The greatest amount of dry matter (>4 t/ha) with an N co ntent of 29 kg/ha was found following pure vetch and sorghum and the lowest dry matter (3.4 t/ha) and N (23 kg/ha) following pure barley and sorghum. At AZRC, the same trends in sorghum were observed as at NARC but with reduc ed yields due to the substantially lower and less well distributed rainfall and suboptimal temperatures, which restricted the productivity of the init ial crops in the sequence.