A Study On Efficient Forage System In Cropping Areas Of Southwest China

There has been an increasing demand for high-quality forages with the rapid development of livestock production and change in farming systems in cropping areas of Southwest China, and the establishment of efficient forage systems is a urgent need for livestock development. From September 2002 through September 2003, a field experiment was carried out in Hongya, Sichuan Province, in which six forage systems were established by combining cool-season and warm-season annual forage species into seasonal rotations in order to have a better utilization of the environmental resources, to increase the production per unit area, and to overcome the limitations of perennial species which are subject to a poor survival either in hot summer (temperate perennials) or winter (tropical perennials). The productivity, forage growth rate, leaf area index (LAI), photosynthesis, and the cost and profit of the 6 forage systems were studied. The forage systems studied in this current experiment included ryegrass-corn (RC), ryegrass-sorghumxsudangrass (RS), triticale-corn-corn (TCC), triticale- sorghumxsudangrass (TS), ryegrass+vetch-corn (RVC), and ryegrass+vetch-sorghum x sudangrass (RVS).The forage systems, except RS and RVS, all gave an annual total forage yield over 30 t DM per hectare, with the highest from TS which was 36.7 t DM per hectare. The coupling of warm- and cool-season species led to a prolonged productive season over 300 days for all the systems, even over 360 days in some of the systems.The content of crude protein in forage dry matter were over 10% in all the species included in the experiment, with that of cool-season from 20% to 30%, and warm-season species ranging from 7.9% to 15%, which are much high than the unimproved forage species in South China. The total annual crude protein production ranged from 4 200-7 000 kg per hectare among the six forage systems.For all the forage systems tested, the content of soil organic matter increased as compared with the level before the experiment, the level of total N P and K and available N in the soil did not change much over the period of the experiment, while the level of available P and K was higher in soil when the growing crop was warm-season species than when it was cool-season forages.Relative to ryegrass, triticale is less tolerant to frequent cutting and the regrowth declined when shoots of triticale were frequently harvested. The average daily growth rate was as low as 9.0 kg DM/hm2.d, 15.1 kg DM/hm2.d and 7.0 kg DM/hm2.d in late autumn (late October) for ryegrass, triticale and ryegrass+vetch, respectively, and was as high as92.9 kg DM/hm2.d, 79.0 and 90.0 kg DM /hmld, respectively in order.The mean leaf angle (MLA) of ryegrass and ryegrass+vetch ranged from 35 to 50, that of triticale from 34 to 57, sorghumxsudangrass from 31 to 49, and com from 10.98 to 44.48. The result of a stepwise regression showed that LAI had the highest contribution to the change in light trans-coefficient in the sward, and followed by MLA and plant height.Over the growth season, the net photosynthesis rate (Pn) of ryegrass reach a peak in Mid- December, while Pn of triticale reach its peak in November and December, and was generally higher than that of ryegrass.The highest profit was obtained from TC system, with a net income of 3.12 times of that of rice-rape system, and 1.87 times of that of rice-ryegrass system. The net income of RVS system was the lowest, but it is still as much as rice-rape system, and 1,22 times of rice-ryegrass system.