1 Vandermeer J. The Ecology of Intercropping. New York: Cambridge University Press, 1989
[2]
2 Knoerzer H, Graeff-Hoenninger S, Guo B, et al. The rediscovery of intercropping in China: a traditional cropping system for future chinese agriculture-A review. In: Lichtfouse E, ed. Climate Change, Intercropping, Pest Control and Beneficial Microorganisms. New York: Springer, 2009. 13-44
[3]
3 Hauggaard-Nielsen H, Jensen E S. Facilitative root interactions in intercrops. Plant Soil, 2005, 274: 237-250
[4]
4 Li L, Li S M, Sun J H, et al. Diversity enhances agricultural productivity via rhizosphere phosphorus facilitation on phosphorus-deficient soils. Proc Natl Acad Sci USA, 2007, 104: 11192-11196
[5]
5 R？mheld V, Marschner H. Evidence for a specific uptake system for iron phytosiderophores in roots of grasses. Plant Physiol, 1986, 80: 175-180
[6]
6 Zuo Y M, Zhang F S, Li X L, et al. Studies on the improvement in iron nutrition of peanut by intercropping with maize on a calcareous soil. Plant Soil, 2000, 220: 13-25
[7]
7 An L Y, Pan Y H, Wang Z B, et al. Heavy metal absorption status of five plant species in monoculture and intercropping. Plant Soil, 2011, 345: 237-245
[8]
8 White P J, Broadley M R. Biofortifying crops with essential mineral elements. Trends Plant Sci, 2005, 10: 586-593
[9]
9 Pixley K V, Palacios-Rojas N, Glahn R P. The usefulness of iron bioavailability as a target trait for breeding maize (Zea mays L.) with enhanced nutritional value. Field Crop Res, 2011, 123: 153-160
[10]
10 Feil B, Moser S B, Jampatong S, et al. Mineral composition of the grains of tropical maize varieties as affected by pre-anthesis drought and rate of nitrogen fertilization. Crop Sci, 2005, 45: 516-523
[11]
11 Bouis H E, Hotz C, McClafferty B, et al. Biofortification: a new tool to reduce micronutrient malnutrition. Food Nutr Bull, 2011, 32: S31-S40
[12]
12 Bruns H A, Ebelhar M W. Nutrient uptake of maize affected by nitrogen and potassium fertility in a humid subtropical environment. Commun Soil Sci Plant Anal, 2006, 37: 275-293
[13]
13 Li H, Huang G, Meng Q, et al. Integrated soil and plant phosphorus management for crop and environment in China. Plant Soil, 2011, 349: 157-167
[14]
14 Cordell D, Drangert J O, White S. The story of phosphorus: global food security and food for thought. Glob Environ Change, 2009, 19: 292-305
[15]
15 Stukenho D D, Olsen R J, Gogan G, et al. On the mechanism of phosphorus-zinc interaction in corn nutrition. Soil Sci Soc Am Proc, 1966, 30: 759-763
[16]
16 Ryan M H, McInerney J K, Record I R, et al. Zinc bioavailability in wheat grain in relation to phosphorus fertiliser, crop sequence and mycorrhizal fungi. J Sci Food Agric, 2008, 88: 1208-1216
[17]
17 Fan M S, Zhao F J, Fairweather-Tait S J, et al. Evidence of decreasing mineral density in wheat grain over the last 160 years. J Trace Elem Med Bio, 2008, 22: 315-324
[18]
18 Pleijel H, Danielsson H. Yield dilution of grain Zn in wheat grown in open-top chamber experiments with elevated CO2 and O3 exposure. J Cereal Sci, 2009, 50: 278-282
[19]
19 Kutman U, Yildiz B, Cakmak I. Effect of nitrogen on uptake, remobilization and partitioning of zinc and iron throughout the development of durum wheat. Plant Soil, 2011, 342: 149-164
[20]
20 Cakmak I, Kalayci M, Kaya Y, et al. Biofortification and localization of zinc in wheat grain. J Agric Food Chem, 2010, 58: 9092-9102
[21]
21 Peterson C J, Johnson V A, Mattern P J. Evaluation of variation in mineral element concentrations in wheat-flour and bran of different cultivars. Cereal Chem, 1983, 60: 450-455
[22]
22 Calderini D F, Ortiz-Monasterio I. Grain position affects grain macronutrient and micronutrient concentrations in wheat. Crop Sci, 2003, 43: 141-151
[23]
23 Shi R L, Weber G, Koster J, et al. Senescence-induced iron mobilization in source leaves of barley (Hordeum vulgare) plants. New Phytol, 2012, 195: 372-383
[24]
24 Uauy C, Distelfeld A, Fahima T, et al. A NAC gene regulating senescence improves grain protein, zinc, and iron content in wheat. Science, 2006, 314: 1298-1300
[25]
25 Oikeh S O, Menkir A, Maziya-Dixon B, et al. Genotypic differences in concentration and bioavailability of kernel-iron in tropical maize varieties grown under field conditions. J Plant Nutr, 2003, 26: 2307-2319
[26]
26 Oikeh S O, Menkir A, Maziya-Dixon B, et al. Environmental stability of iron and zinc concentrations in grain of elite early-maturing tropical maize genotypes grown under field conditions. J Agric Sci, 2004, 142: 543-551
28 Li L, Sun J H, Zhang F S. Intercropping with wheat leads to greater root weight density and larger below-ground space of irrigated maize at late growth stages. Soil Sci Plant Nutr, 2011, 57: 61-67
