Managing Global Resources for a Secure Future

Agroforestry has been practiced widely to reduce wind erosion and efficiently use natural resources, e.g. land, light and water, especially in semi-arid windy regions. However, limited knowledge on optimizing mixing crop species (i.e. C3 and C4, legume and none legume) to achieve maximal resource capture and use efficiency for light and water in a fragile ecosystems are available. We conducted field experiments in 2012 to 2013 in the semi-arid Khorchin region in Liaoning, China to quantify crop yield, land equivalent ratio (LER), light interception(LI), light use efficiency(LUE), water use efficiency(WUE) and photosynthesis of mixing C3 and C4 and legume crops with apricot (Prunus armeniaca). The mixing crops were millet (Pennisetum italica), peanut (Arachis hypogaea) and sweet potato (Ipomoea batatas). Apricot yields were not significantly affected in the agroforestry, compared to the sole stand, but yields of the annual crops were lower when grown under trees than as sole crops, with relative crop yields of 0.46 for millet and 0.35 for both peanut and sweet potato in the agroforestry. LERs were 1.34, 1.44 and 1.33 in mixed systems with peanut, millet and sweet potato, respectively. A significant delay of leaf growth was found in the mixture of millet, while the growth delay were not significant in peanut and sweet potato. As a result of this temporal niche differential in leaf growth, maximum LAI of millet was 17% higher in the agroforestry comparing with the sole stand, while a significant 25% decrease was observed across intercropped peanut and sweet potato. In the agroforestry, The light interception in total in agroforestry was 54% higher than in sole tree and 23% higher than in sole crops respectively. The millet intercepted more light and produce more biomass than peanut and sweet potato. The LUEs of mixing crops at field level were significantly higher than of sole crops, which was also convinced by LUE at organ level, as photosynthesis rate (Pn) over absorbed PAR by individual leaves, especially in plants at border rows. Mixing crops and trees did not increase water extraction, but significantly improved WUEs. Water equivalent ratios (WERs), analogous to LER as the relative yield total per unit of water, were 1.39, 1.51, and 1.34 in agroforestry systems with peanut, millet and sweet potato, respectively. We concluded that the apricot and annual crops agroforestry could efficiently use natural resources (land, light and water) of rain-fed agriculture in semi-arid climate and would play an important role on regional sustainability and adaption to climate change, especially when a drought adapted crop such as millet is used.