4 Aleksandra Głowacka
suffer from deficiencies of mineral components, such as iron, zinc, iodine,
copper, selenium, calcium and magnesium. These deficiencies are caused by
diets characterized by high intakes of staple foods but low intakes of
vegetables, fruits, and animal and fish products, which are rich sources of
minerals (White and Brodly 2009). The density and bioavailability of
micronutrients in the diet are important for achieving optimal micronutrient
status. Nutrient density is the amount of a nutrient in a food per unit weight.
Bioavailability is the proportion of an ingested nutrient that is absorbed and
utilized for some essential metabolic function (Miller and Welch 2013).
Traditional strategies to deliver these mineral nutrients have mainly relied on
mineral supplementation, dietary diversification, and food fortification (Welch
and Graham 2004, White and Broadly 2005). To date, these efforts have had
limited success due to a lack of social, cultural, and economic infrastructure.
They require safe delivery systems, stable political policies, appropriate social
infrastructures and continued investment. An alternative complimentary
solution to mineral malnutrition is “biofortification.” Biofortification has been
defined as the process of increasing the bioavailable concentrations of
essential elements in edible portions of crop plants through agronomic
intervention or genetic selection (White and Brodly 2005, Waters and
Sankaran 2011). According to Zuo and Zhang ( 2009 ) biofortification can be
achieved by utilizing crop and soil management with plant breeding to
increase nutrient concentrations in the edible parts of crops. The concept of
biofortification is attractive not only for improving the growing conditions of
crops but also for exploiting a plant’s potential for micronutrient mobilization
and utilization. In addition to mineral fertilization, conventional breeding and
transgenic plants, intercropping between dicots and gramineous species would
be the key to some staple crops biofortification.
THE EFFECT OF STRIP INTERCROPPING SYSTEMS ON
THE YIELD
Maize is a species frequently selected for strip cropping because it reacts
strongly to the edge effect and, as a tall, C4 photosynthesis plant, makes
efficient use of the greater amount of sunlight. Yield in the edge rows
increases substantially, by as much as 50%, and thus the total yield from the
strip is greater as well (Cruse and Gilley 1996, Lesoing and Francis 1999). The
increase in yield also depends on the position of the row in the strip and on the