Density and irrigation studies in Lupinus albus and L. angustifolius

Abstract

Interest in sweet lupins as a possible source of high quality protein prompted the studies reported in this thesis. At the time of the inception of these studies several scientific groups in Australia and New Zealand were proceeding with agronomic evaluations of several lupin species, but sowing rates had not been defined. In Canterbury lupins grown for seed have been autumn-sown but with the release of early flowering cultivars spring sowings were possible. Thus several density experiments were carried out with Lupinus albus and L. angustifolius to determine yield characteristics. In some experiments the possibility of irrigation responses was also evaluated.

The thesis begins with a review of previous lupin studies, a review of the current knowledge of density relationships in grain legumes and contains a section on crop-water relations. The remaining chapters, with the exception of the final concluding summary in Chapter Thirteen, discuss results of spring-sown experiments over two seasons. Each of these chapters (Two to Twelve) is a complete unit where literature relevant to the topic is briefly reviewed, the methodology outlined and the results are presented and discussed.

Preliminary trials at Lincoln College with L, angustifolius had suggested responses to densities above 30-40 plants m⁻² recommended by Gladstones (1971). No information was available for the larger seeded L, albus. Thus the first experiment (Chapter Two) in the 1975-76 season was designed to investigate development and seed yield patterns in Ultra, the early flowering L, albus cultivar, at six plant densities. The second 1975-76 experiment examined growth and development patterns (Chapter Three), and components of seed yield (Chapter Four) of L. angustifolius cv, WAU11B, at densities over the range of 27-156 plants m⁻², In this experiment an irrigation treatment was also imposed at flowering.

Seed yields from the L. angustifolius experiment were higher than reported yields in the literature. It was therefore decided to follow up this research with a similar experiment in the 1976-77 season. Seed yield characteristics of this density x irrigation experiment with Unicrop (L. angustifolius) are discussed in Chapter Seven, while in Chapter Eight there is a discussion of growth and development patterns in both Ultra and Unicrop. Chapters Five and Six discuss two relationships which might have affected density responses. The experimental area in the 1976-77 season was infested with perennial and annual weeds. The annual weeds in all but one experiment were controlled by herbicide application, but perennial weed growth, although not apparently affecting seed yield, was only suppressed in medium and high density lupin plots (Chapter Five).

The second relationship is that plant density is composed of two factors: absolute density and spatial arrangement. These were examined in a row width x density experiment (Chapter Six).

A redistribution of the major elements (N, P, K, S) from leaves to filling seeds may contribute to premature leaf senescence, Foliar fertilisation at this time may extend the photosynthetically active life of leaves and be the cause of increased yields in soybeans. The results of a preliminary experiment designed to evaluate foliar fertilisation and irrigation at flowering and pod filling stages in Ultra and Unicrop are discussed in Chapter Nine.

Pod formation is more responsive to density changes than other yield components. Lupins exhibit an indeterminate growth pattern which may contribute to high levels of flower abscission. Results of an experiment where vegetative buds were removed at flowering in Ultra and Unicrop are presented in Chapter Ten. Chapter Eleven examines the indeterminate growth pattern in both species with special reference to flower development, while in Chapter Twelve there is a detailed appraisal of seed yield components.