Nodulation, N₂ Fixation, and Seed Yield of Navy Beans as Influenced by Inoculant Rate and Inoculant Carrier¹

Abstract

Peat is the most commonly used carrier of Rhizobium sp. (rhizobia) in inoculants. The lack of suitable local peat in many areas of the world leads to interest in other materials as carriers of rhizobia. The purposes of these studies were 1) to compare potential carriers of Rhizobium phaseoli for their ability, under field conditions, to supply viable rhizobia to promote nodulation, N2 fixation, and increased seed yield of navy beans (Phaseolus vulgaris L.), and 2) to determine the optimum rate of inoculation with Rhizobium phaseoli to promote nodulation, N2 fixation, and increased seed yield of navy beans in two soils in Minnesota, a loamy sand (sandy, mixed, Udorthentic Haploborall) and a silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludoll). In 1978, five inoculation rates (ranging from 1 to 108 cells/ cm of row) of liquid suspensions of R. phaseoli inoculants were applied at planting. In 1979, R. phaseoli in six inoculant carriers, peat, charcoal, vermiculite, corn (Zea mays L.) cobs, peanut (Arachis hypogaea L.) hulls, and liquid medium, was used to inoculate navy beans at rates of 2.5 ✕ 104 and 5 ✕ 106 cells/cm of row. Nodule numbers and weight, acetylene reduction rates, seed yield, and seed N percentage were determined. In 1978, in most parameters measured, inoculation rates of 105—106 cells/ cm were required for a statistically significant increase over the lowest inoculation rate. In 1979 there was no effect of inoculation on a soil with a relatively high population of soil R. phaseoli (104 cells/g soil) and relatively high mineral N content (30 ppm). On a soil with an indigenous population of <10 cells/g soil and mineral N content of 8 ppm, peat and charcoal inoculants resulted in the highest seed yield, nodule numbers and weight, and acetylene reduction rates. Peanut hulls and corn cobs gave the poorest responses. These results indicate that peat, charcoal, and vermiculite can be successfully used as carriers of R. phaseoli but peanut hulls and corn cobs are unsatisfactory.

Dinitrogen Fixation by Seven Legume Crops in Alaska

“…On the other hand, a farmer will want to make maximum use of the N2-fixation potential of the crop. In temperate regions, nitrogenase activity by pulse legumes has been shown to peak near or soon after flowering and then decrease rapidly during pod-fill (Westermann and Kolar, 1978;Dean and Clark, 1980;Sparrow and Ham, 1983;Vessey, 1991), while other legume species and specific cultivars had sustained activity well into pod-filling (Dean and Clark, 1980;Vessey, 1991;Vikman and Vessey, 1992). A decrease in nitrogenase activity after flowering also has been reported for forage-type legumes (Martensson and Ljunggren, 1984;Machova, 1992).…”

“…The acetylene reduction (AR) assay was used to determine nitrogenase activity at regular intervals throughout the growing season. Acetylene reduction assays were begun ""'25 d after planting, and were continued every 2 wk until harvest, following the method of Sparrow and Ham (1983). Soil cores measuring 15 em in diameter by 15 em long and containing plant root samples were incubated in 3.8-L plastic buckets for 1 h after addition of 120 mL acetylene.…”

Identification and characterization of common bean (Phaseolus vulgaris L.) lines well nodulated in the presence of high nitrate

“…Rhizobia inoculation of bean seed to facilitate nodulation and N2 fixation by the bean plant generally has not increased seed yield (Diatloff and Saint-Smith, 1981;Huntington et al, 1986;Weiser et al, 1985) although a few authors reported increased seed yield (Sparrow and Ham, 1983;Taylor et al, 1983).…”

Influence of the Size of Indigenous Rhizobial Populations on Establishment and Symbiotic Performance of Introduced Rhizobia on Field-Grown Legumes

“…Inoculation of legumes with exotic strains of rhizobia is a common agricultural practice intended to promote nitrogen fixation and increase crop yield. Despite improvements in inoculation methods (3,13,31,34) and selection of rhizobial strains for increased nitrogen fixation capacity (16), competitive ability (1), and ability to withstand environmental stress (15,17,19), inoculation does not always lead to increased plant growth and crop yield.…”