When averaged over a wide range in soil nitrogen and moisture conditions, cultivar differences in yield and protein content of non-inoculated field peas (Pisum sativum L.) were relatively small. The inherent differences in seed weight were responsible for most of the variations in yield among the three cultivars. Nitrogen fertilization in the growth room experiment markedly increased plant weight, seed yield and protein content, and water-use efficiency was substantially improved. When maintained within the upper half of the available range, soil moisture supply had only a limited influence on plant growth. Periodic wilting did cause a severe reduction in plant weight and seed yield, but there was little change in protein content. For these fertilizer and moisture treatments, responses in seed yield were primarily due to changes in number of pods per plant; the seeds per pod and seed weight were relatively stable. It appeared that field peas were efficient converters of soil nitrogen to seed protein and, in the absence of nitrogen-fixing bacteria, nitrogen fertilization was the principal factor influencing the protein content of field peas. The correlation coefficient between yield and protein content was very low.
Combining Ability and Heterosis of Algerian Saharan Maize Populations (Zea mays L.) for Tolerance to No-Nitrogen Fertilization and Drought
