Nodulation and nitrogen fixation by Vigna sinensis and Vicia atropurpurea: The influence of concentration, form, and site of application of combined nitrogen

Abstract

Nitrogen fixation by Vigna sinesis nodulated effectively either by Rhizobium strain QA323 or by strain CB441 is little restricted by applications at sowing of ammonium nitrate up to 24 mg nitrogen per plant. The growth patterns of these two associations are differentially affected by nitrogen level, and are both considerably different from that of unnodulated plants given combined nitrogen. Nitrogen fixation by V. sinensis-strain SU318 may be stimulated by small doses of combined nitrogen at sowing, but for Vicia atvopurpurea all the combined nitrogen levels used in these experiments depressed fixation. Primary root nodulation of V. atropurpurea by the effective Rhizobium strain V27E and the ineffective strain NA6, and of V. sinensis by the effective Rhizobium strain SU318, is influenced by the form and amount of the nitrogen compound applied (ammonium nitrate, potassium nitrate, ammonium sulphate, or urea), and that of V. atropurpurea is also influenced by the Rhizobium strain. These forms of combined nitrogen restrict primary root nodulation on both hosts similarly except that urea has little effect on V. atuopurpurea. In both species many more nodules formed on the secondary roots than on the primary, but numbers of secondary root nodules are little affected by the combined nitrogen. Immersion of the first leaves of V. sinensis seedlings in solutions of combined nitrogen depressed nodulation, but urea slightly increased the dry weight of tops.

A Supernodulation and Nitrate-Tolerant Symbiotic (nts) Soybean Mutant

“…Mutant medium (20). To a lesser extent, other sources of combined nitrogen have also been shown to inhibit nodulation (7,8,10, 24,27). The extent of this inhibition does vary considerably with the legume species, the form of combined nitrogen administered, and the experimental system.…”

Soybean response to nitrogen fertility, photoperiod, root pruning, kinetin and shoot apex removal

“…and nodules associated with a corresponding increase in root weight. The involvement of supplemental combined nitrogen on nodule development has been well established (Thimann, I936, 1939;Nutman, 1956;Tanner and Anderson, 1964;Dart, 1970), Reduction in nodulation by combined nitrogen is well documented by Thornton (1946), Virtanen (1953)» Schreven (1959)» Dart (1965 and Weber (1966a and 1966b). The majority of the work reported was done either under artificial growth conditions or with nitrogen applied very early (close to or at planting time).…”

“…The majority of the work reported was done either under artificial growth conditions or with nitrogen applied very early (close to or at planting time). It can be seen in Table 32 that nitrogen had no mea sured effect upon these variables designed to measure nodule numbers and mass (Dart, 1970;Mishra and Singh, I968). This is in direct contrast to the findings of Thornton (1946) andWeber (1966b).…”

“…Mishra and Singh (I968) in more recent data reported that the addition of nitrogen to soybeans as late as 80 days after planting caused a decrease in the number of nodules per plant. Dart and Wildon (1970) effectively inhibited nodulation with aerial application of nitrogen fertilizer to actively growing plants. Increasing levels of nitrogen and associated reduction in number of nod ules formed was well documented by Thornton (1946).…”

“…With the reported negative effects of nitrate on nodulation (Thimann, 1936(Thimann, , 1939Stewart, I966;Tanner and Anderson, 1964;and Dart and Wildon, 1970), nodule formation (Thornton, 19^6;and Dart and Wildon, 1970) and leg hemoglobin requirements for active nodules, it was assumed that total nodule number, NOo in ppm, percentage N and leghemoglobin activity were inseparably interrelated and do not act independently of each other. Figure 9t> is an attempt to show the related variation of these factors over these dates of sampling early in plant development.…”