Li Feng-Min

Economic analysis of rainwater harvesting and irrigation methods, with an example from China

The purpose of this paper is to evaluate the economic feasibility of agriculture with rainwater harvesting and supplemental irrigation in a semiarid region. The results show the importance of making full use of every open-air hardened surface to collect rainwater and to establish rainwater catchment areas by utilizing unoccupied land. The results also show that the usefulness of the harvested rainwater is enhanced when water saving and prevent seepage techniques are employed. The results indicate that in order to maximize investment it is essential to select crops with a water requirement process that coincides with local rainfall events. Potato was found to be the most suitable crop in the studied region. The economic indices for potato were superior to spring wheat, corn and wheat/corn intercropping. Therefore, potato production using rainwater harvesting and supplemental irrigation is the best alternative for cropping systems in the semiarid region of Gansu, China.

Availability and contributions of soil phosphorus to forage production of seeded alfalfa in semiarid Loess Plateau

Abstract The availability of soil phosphorus was studied in response to the forage production of seeded alfalfa ( Medicago sativa L.), established by the ridge and furrow water-harvesting technique in the semiarid Loess Plateau of China. The following 5 treatments were set up in this study: (1) conventional cultivation in a flat plot without mulch (CK); (2) plastic mulched ridge with 30 cm width of ridge and furrow (M30); (3) plastic mulched ridge with 60 cm width of ridge and furrow (M60); (4) bare ridge with 30 cm width of ridge and furrow (B30); (5) bare ridge with 60 cm width of ridge and furrow (B60). The forage yield, evapotranspiration (ET), soil organic carbon (SOC), total phosphorus, available phosphorus and the ratio of soil organic C to available P (C/P) were measured in the experiment. Results showed that the positive correlation occurred between the decrease in soil available P and the total forage yield of alfalfa after three-year alfalfa stand. M30 and M60 were higher than those of conventional flat cultivation (CK) by 10.7% and 40.3%, respectively, whereas the yield of two bare treatments (B30 and B60) was lower than that of CK by 14.2% and 28.3%, respectively. After a 3-year alfalfa stand, the trend of the decrease in soil available P was in the order of M60 (55.5%) > M30 (51.5%) > CK (34.6%) > B30 (23.4%) > B60 (17.5%). Moreover, after 3-year alfalfa growth, the C/P ratio increased significantly in all of the treatments by comparing with that before sowing. The C/P ratios of M30 (1165.1) and M60 (1326.1) were significantly higher than those of the other treatments. More interesting finding was that the increase in SOC in dry years promoted the accumulation of soil available P. However, in wet years, the increase of SOC limited the accumulation of soil available P. Therefore, to further increase the forage yield of alfalfa, the effective technique must be developed to increase the soil available P.

Effects of water supply in the upper and lower soil profiles of deep soil on root characteristics and dry matter production of winter wheat

The purpose of this research was to test (1) the effect of supplying water in deep soil on wheat plant growth; (2) the modifying effect of root dry-matter allocation of wheat plants on shoot growth; and (3) the possibility of improving grain yield by using deep soil water. The experiment was conducted at the Northwest Institute of Soil and Water Conservation, Academia Sinica, and the Ministry of Water Conservancy, Yangling Shaanxi, P.R. China. Wheat plants were grown in 30-cm long, 7-cm wide, and 200-cm tall growth chambers which were divided into two layers at 1-m soil depth. The experiment included four treatments: (a) both soil layers were wet close to capacity (WW); (b) both layers were dry (DD); (c) the upper layer was wet and the lower layer was dry (WD); and (d) the lower layer was wet and upper soil was dry (DW). Soil water content in upper and lower layers after seven days of treatment measured 23.47% in WW, 15.01% and 13.90% in DD, 18.57% and 15.70 in WD, and 19.46% and 25.98% in DW. The experiment lasted for 68 days, in which period there was no additional water supply to the growth chambers. The experiment showed that DW treatment maintained the highest water content of both soil and plant, and produced a larger root system. In the DW lower soil level, root dry matter was the highest among the four treatments. Also, the dry weights of flat leaves and spikes were highest in the DW treatment. The results indicate that the DW treatment has the greatest yield potential. A soil water regime of dry upper soil and wet lower soil is beneficial for the initiation of root chemical signals and for a balance of water utilisation in the growth cycle. It promotes root development in deep soil and thus helps improve yield and water use efficiency.