James E. Bidlack

NODULATION, NITROGENASE ACTIVITY, AND DRY WEIGHT OF CHICKPEA AND PIGEON PEA CULTIVARS USING DIFFERENT BRADYRHIZOBIUM STRAINS

Chickpea [Cicer arietinum (L.)] and pigeon pea [Cajanus cajan (L.) Millsp.] were grown outside in large clay pots from 1992 to 1995 in Edmond, Oklahoma. Plants were studied to evaluate nodulation, nitrogenase activity, and shoot dry weight (DW) of ‘ICCV-2’ and ‘Sarah’ chickpea inoculated with multistrain, TAL 1148, and TAL 480 Bradyrhizobium, as well as ‘Georgia-1’ and ‘ICPL-87’, pigeon pea inoculated with multistrain TAL 1127, and TAL 1132 Bradyrhizobium. Following wheat [Triticum aestivum (L.) emend. Thell.] harvests in the spring, legumes were planted in the summer and harvested at three successive dates during the following months. Leaves and stems from remaining plants were incorporated into the soil after the last harvest. Across year, chickpea measurements were sensitive to temperature and precipitation whereas pigeon pea measurements were sensitive to length of growing season as well as climate. Pigeon pea consistently demonstrated higher nitrogen-fixing capacity and shoot DW compared with chickpea. Nodule and shoot DW of both species increased with plant age whereas nodule count and nitrogenase activity generally increased with plant age and leveled off or decreased at flowering. Sarah chickpea demonstrated higher nodule count and nodule DW than ICCV-2, as did the Georgia-1 pigeon pea compared with ICPL-87. Shoot DW of Georgia-1 pigeon pea was generally higher than that of ICPL-87. Multistrain inoculum improved nodulation and shoot DW of chickpea, and TAL 1127 improved nodulation of pigeon pea compared with other treatments. These results indicate that specific chickpea and pigeon pea cultivars, along with appropriate Bradyrhizobium strains, may improve nitrogen fixation and DW of these species.

Biomass and nitrogen traits of summer pigeon peas and winter wheat grown for three rotations in containers

Pigeon pea [Cajanus cajan (L.) Millsp.] cultivars, ‘Georgia-1’ and ‘ICPL-87’, were grown without inoculation and with Bradyrhizobium inoculation (multistrain, TAL 1127, or TAL 1132) to evaluate legume dry weight (DW) and nitrogen (N) content, soil mineral N, and subsequent wheat (Triticum aestivum L.) productivity. Pigeon peas were grown during summer and ‘TAM 101’ wheat was grown during winter, along with summer fallow controls fertilized with 0, 45, and 90 kg N ha− 1, in 36-cm diam. 20-L pots from 1992 to 1995. Representative pigeon peas were harvested in the fall and remaining plants were incorporated into the soil. Wheat was planted and soil cores were collected at 35 to 48 d after pigeon pea harvest. Wheat was harvested the following spring. Factors affecting DW and N content of both crops included length of growing season, environmental variation, and contribution of residual N. Among pigeon pea cultivars, Georgia-1 occasionally demonstrated higher DW and N content compared with ICPL-87. Estimation of N provided by pigeon pea to the last wheat crop in the third sequence of yearly rotations was 30 kg N ha− 1. Pigeon pea treatments demonstrating highest DW, N content, and contribution to soil N generally produced winter wheat with higher yield and N content compared with other treatments. While yield and N content of winter wheat fertilized at 90 kg N ha− 1 either decreased or stayed the same from 1993 to 1995, these same measurements in wheat following pigeon peas demonstrated a 3- to 4-fold increase over the same time period and warrant further research in field rotation systems of the southern Great Plains.

Dry Weight and Nitrogen Content of Chickpea and Winter Wheat Grown in Pots for Three Rotations

ABSTRACT Chickpea [Cicer arietinum (L.)] cultivars ‘ICCV-2’ and ‘Sarah’ were studied along with a control, multistrain, TAL 1148, and TAL 480 Bradyrhizobium strains to determine the effect(s) of cultivar and inoculum on dry weight (DW) and nitrogen (N) content of the legume, as well as soil mineral N, DW, and N content of wheat [Triticum aestivum (L.) emend. Thell.] in a continuous wheat-legume rotation. Chickpeas were planted during the summer and harvested in the fall of 1992, 1993, and 1994. Vegetative growth from chickpeas was incorporated into the soil prior to wheat planting, and soil cores were taken at 35 to 48 d after chickpea harvests. Additional summer fallow treatments for the winter wheat part of the experiment received 0, 45, and 90 kg N ha−1 each year. Wheat plants were removed the following spring and stubble was incorporated into the soil before planting chickpeas in the summer. ‘Sarah’ chickpeas accumulated about the same or more shoot DW and shoot N compared to ‘ICCV-2’; whereas ‘ICCV-2’ generally produced more pod DW and pod N compared to ‘Sarah.’ Inoculum had no significant effect on chickpea DW or N content. Wheat DW and N following legumes increased marginally after growing ‘Sarah’ chickpeas, as evidenced by higher values of some treatments. Only the multistrain or absence of inoculum in ‘Sarah’ chickpeas resulted in significantly greater wheat DW or N content compared to the fallow wheat receiving no added N fertilizer. The contributions from ‘ICCV-2’ chickpeas to wheat DW and N content were not significant. Soil mineral N, as well as wheat DW and N content, fluctuated or increased during this three-year study, which demonstrated some benefit from incorporation of chickpeas into a wheat-legume cropping system.

Morphology, Biomass, and Vessel Diameter of Pigeon Pea Subjected to Water Stress

This research was designed to study the effects of drought on pigeon pea [Cajanus cajan (L.) Millsp.] morphology, biomass, and vessel diameter. Cultivated seeds of pigeon pea (cv. Georgia-II) were germinated, maintained in an environmental chamber, and arranged as a split-plot design with four replications; harvest was the main effect and watering regimens were tested against residual error. Plants were watered every 2, 4, 8, 16, or 32 days. Number of stems and leaves, as well as total plant height, were measured weekly. Dry weight (DW) of roots, stems, and leaves were recorded at each harvest, and root cross sections were viewed to determine vessel diameter. Results indicated that plant morphology, biomass, and vessel diameter were significantly affected by harvest and watering regimen. Plants watered more frequently had more stems and leaves, grew taller, accumulated greater DW, and had larger diameter vessels within root tissue.

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Two clones of Mentha arvensis L., both with 2n = 72 from Europe, one with 49.20 ′ 2.28% pulegone, another with 57.31 ′ 9.41% linalool, were hybridized with M longifolia (L.) L. from Europe with 2n = 24 and 51.87 ′ 0.50% trans-piperitone oxide. The F 1 hybrids had essential oils rich in pulegone, isomenthone, menthone, trans-isopulegone, menthol, neomenthol, 3-octanol, linalool, cis-piperitone oxide, trans-piperitone oxide, carvone, limonene, piperitenone oxide, trans-carveol, trans-sabinene hydrate, 3-octanone, terpinen-4-ol, (Z)-β-ocimene, geranyl acetate, citronellyl acetate, and/or β-caryophyllene. Thirty-nine F 1 hybrids of this cross are similar to 23 clones of M canadensis L. from North America and Asia with 2n = 96 when compared by chromosome numbers, morphology, and essential oils. Mentha canadensis is proposed as a relict amphidiploid of the mixed mesophytic flora of the Lower Tertiary.