The responses of two cowpea (Vigna unguiculata (L.) Walp.) cultivars inoculated with granular inoculum (a mixture of rhizobia) at different levels of applied nitrogen were evaluated. California Blackeye 5 (Ca5) and Knuckle Purple Hull (KPH) cowpeas were examined under field conditions for percent nodulation, nodule number, and nodule mass per plant, and nitrogenase activity at various times during the 1983 and 1984 growing seasons. Data were also obtained for shoot and root dry weights, seed yield, and protein content. Significant differences between inoculated and uninoculated plots were found at all nitrogen treatments for both cultivars with respect to nodulation percentage, nodule number, nodule mass, and nitrogenase activity. An inverse trend linear and quadratic was noted between nitrogen increments and nodulation (nodule number and nodule mass) of Ca5 and KPH cowpeas. High N (168 kg N ha('-1)) was more inhibitory to nodulation than low (28 kg N ha('-1)) N applied. Nitrogenase activity of both cultivars was significantly stimulated with low and inhibited by high levels of ammonium nitrate. Effects of nitrogen treatments on nodulation and nitrogenase activity were influenced by the stage of growth and cowpea cultivar. At the pod-fill stage, higher nodule numbers and nitrogenase activity were recorded for Ca5 as compared to KPH cowpeas. Morphological differences, with Ca5 plants being erect with few vines, whereas KPH plants were semi-erect and bushy, were observed between inoculated and uninoculated plants of Ca5 and KPH cowpeas at all levels of applied nitrogen. Dry weights of vegetative components of both cultivars were significantly improved when low (28 kg N ha('-1)) rather than high (168 kg N ha('-1)) nitrogen was added. Inoculation significantly increased seed yield of Ca5 cowpeas. When conditions were favorable seed yield of inoculated Ca5 exceeded that of inoculated KPH in all comparisons within the same increments of applied N. Seed yield of both cultivars was adversely affected when high levels of nitrogen were applied. Seed, leaf, petiole, and stem protein content were significantly higher with respect to inoculated than uninoculated plots. However, nitrogen fertilizers tended to decrease protein content of the measured parameters for Ca5 and KPH cowpeas.

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Intercropping of a short-cycle legume crop and a longer-cycle non-legume crop has been suggested as a potentially beneficial intercrop combination. Most studies have concerned cereal and legume corps. Few have involved horticultural crops. In 1990 and 1991, a 56-day semi-leafless pea crop (Curly) and a 75-day lettuce crop (Paris Island Cos) were grown both as monocrops and as intercrops. Intercrops consisting of alternating rows of each crop, represented additive populations (56:100) of peas and lettuce. Three lettuce transplanting dates (June 19, 25 and July 4) and three nitrogen fertilizer rates (0, 50, 100 kg ha$ sp{-1}$) were tested. Peas were all sown on May 18. In addition, a new pea/lettuce intercropping pattern (45:82), consisting of alternating double rows of peas and lettuce, was tested in 1991. The $ sp{15}$N dilution method was also used to test for nitrogen transfer. Alternate row intercropped lettuce plant$ sp{-1}$ yields were, on average, 76% and 46% lower than their corresponding monocrop yields for the early and late transplanted lettuce, respectively. Declines in yield of 63% and 55% were reported for the double row intercropped lettuce for the early and late transplanting dates, respectively. Nitrogen fertilization significantly improved intercropped fresh lettuce yields but had no effect on monocropped lettuce. Pea yields m$ sp{-1}$ row were unaffected by intercropping. Alternate row land equivalent ratios (LER) ranged from 0.87 to 1.05 and from 1.06 to 1.63, in 1990 and 1991, respectively. The double row LER's ranged from 1.06 to 1.21 in 1991. The higher LER's in 1991 reflected higher pea yields. No evidence of nitrogen transfer to the lettuce crop was detected.

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xv, 207 leaves : tables, graphs, photos ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1977) from the Dept. of Agronomy, University of Adelaide

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 72-77). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1946. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 39-44).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.