Soil and plant factors relating to the poor growth of Lupinus species on fine-textured, alkaline soils - a review

Soil type is an important factor affecting the growth of lupins. Successful lupin cultivation is generally restricted to deep, acid to neutral, coarse-textured soils. Very little is known about the factors affecting the performance of lupins on other soil types. This review attempts to define the major factors controlling the growth of lupins of fine-textured, alkaline soils, with a view to providing a focus for future research. Wild populations of the genus, as a whole, occupy soils of a wide pH and textural range (pH 4-8.5, texture ranging from coarse sands to fine clays), although the majority of populations are found on light soils of sandy loam or loamy sand texture with pH values between 5.5 and 7. Species within the genus have distinct preferences for soils of a narrower range than the genus as a whole. Commercially cultivated species appear to be adapted to a narrower range of soil types than the wild species. Iron nutrition, seedling emergence, and rooting pattern and phenology are the major factors influencing the performance of lupins on fine-textured, alkaline soils. Lupins appear to possess some mechanisms thought to enhance the availability of Fe, nevertheless they suffer severely from Fe deficiency. Conditions prevailing on fine-textured, alkaline soils (poor drainage and aeration, CaCO3) are frequently conducive to Fe deficiency. The epigeal pattern of emergence of lupins is unsuitable to fine-textured soils, particularly if crust formation occurs. The rooting pattern and phenology of lupins is better suited to deep sandy soils than shallow, fine-textured soils, and this exacerbates late-season water stress. A better understanding of these factors may allow breeding and management strategies to be developed which will extend lupin cultivation to a wider range of soils.