Shoitsu Ogata

Biological nitrogen fixation in mixed legume-cereal cropping systems

Cereal/legume intercropping increases dry matter production and grain yield more than their monocultures. When fertilizer N is limited, biological nitrogen fixation (BNF) is the major source of N in legume-cereal mixed cropping systems. The soil N use patterns of component crops depend on the N source and legume species. Nitrogen transfer from legume to cereal increases the cropping systems yield and efficiency of N use. The use of nitrate-tolerant legumes, whose BNF is thought to be little affected by application of combined N, may increase the quantity of N available for the cereal component. The distance between the cereal and legume root systems is important because N is transferred through the intermingling of root systems. Consequently, the most effective planting distance varies with type of legume and cereal. Mutual shading by component crops, especially the taller cereals, reduces BNF and yield of the associated legume. Light interception by the legume can be improved by selecting a suitable plant type and architecture. Planting pattern and population at which maximum yield is achieved also vary among component species and environments. Crops can be mixed in different proportions from additive to replacement or substitution mixtures. At an ideal population ratio a semi-additive mixture may produce higher gross returns.

Cell membrane stability, an indicator of drought tolerance, as affected by applied nitrogen in soyabean

Four soyabean cultivars were grown with two N application rates (50 and 300 kg N/ha) in the field at Hiroshima University, Japan, from June to August 1988. Cell membrane stability (CMS) by the polyethylene glycol (PEG) test, leaf water relations and nutrient concentrations in cell sap and leaf tissues were measured when the plants were 50 days old, in the uppermost fully expanded leaves. Cell membrane stability was higher at the higher N rate, the increase over the lower rate being greater in the cultivars Lee+ and Lee–than in Tamahomare and T201. Leaf water potential was not affected by the higher rate of N application. Osmotic adjustment, which was independent of water stress, was observed with the higher rate of N and it was higher in Lee + and Lee–than in Tamahomare and T201. It is suggested that osmotic potential in leaf tissues may influence CMS measured by the PEG test. Solute concentrations in cell sap and leaf tissues were higher at the higher N rate. Sugar and K were the major contributors to osmotic potential.

Excretion of ureide and other nitrogenous compounds by the root system of soybean at different growth stages

Direct excretion of nitrogenous compounds into a N-free nutrient solution, which was allowed to drip onto the root system of soybean (Glycine max (L) Merr. cv. Kurosengoku) was examined at different growth stages; vegetative, flowering and pod-filling. Considerable amounts of nitrogenous compounds were excreted at all the growth stages, with the highest amount recorded at the pod-filling stage.The root was found to be the major site of N compound excretion and its dry weight was linearly correlated with N amount excreted. Maximum nitrogen excretion rate during vegetative and flowering stages was recorded during the ‘day’, however at the pod-filling stage, the highest was recorded during the ‘night’. Ureide was excreted at all growth stages, but the highest amount was recorded at the pod-filing stage. The root was found to be the active site of ureide excretion. Composition of the total nitrogen examined i. e. ureide, soluble proteins, ammonia and amino acids, was found to be changing during the growth stages, suggesting possible different major pathways of excretion at different plant age. Among the N compounds monitored, were soluble proteins, ammonia and amino acids. Only a few of the several amino acids found in the root tissues were observed in the ‘excreted solution’, notably phosphoserine and phosphoethanolamine, at all the growth stages, whilst γ-amino-butyric-acid and serine were observed in trace amounts during vegetative and flowering stages. Quantitatively the ammonia found in the ‘excreted solution’ was far greater than in the tissues.

Phosphorus absorption and utilization efficiency of pigeon pea (Cajanus cajan (L) Millsp.) in relation to dry matter production and dinitrogen fixation

The effect of P supply on absorption and utilization efficiency of P in relation to dry matter production and dinitrogen fixation was examined in 8 pigeon pea cultivars with different growth duration and a soybean cultivar under field conditions.In all the pigeon pea cultivars, the maximum whole plant dry weight was obtained in a P-deficient soil at 100 kg P ha−1 application. The short duration cultivars had smaller whole plant dry weights at low P rates (5 and 25 kg P ha−1) and poor response to P application compared with the medium and long duration cultivars.Increasing the P application rate significantly increased dinitrogen fixation in all the cultivars. At the low P rates, the total nodule activity (TNA) was lower in the short than in the medium and the long duration cultivars. However, at 200 kg P ha−1 application, dinitrogen fixation did not vary among these cultivars except for one short duration cultivar whichregistered very low values.Dry matter production and dinitrogen fixation are strongly controlled by P absorption ability rather than P utilization efficiency. The low absorption ability of the short duration cultivars is mainly due to poor root development.The high P concentrations in the nodules of all the cultivars suggest that nodules have advantage over host plant interms of P distribution under P deficient conditions.Our results suggest that P plays an important role in dinitrogen fixation through an effective translocation of P to the leaf. Thus when P supply is limited, efficient cultivars obtained reasonably high yield through an effective translocation of the absorbed P to the leaf.

Nitrogen transfer and dry matter production in soybean and sorghum mixed cropping system at different population densities

Abstract Field experiments were conducted to examine the effects of mixed cropping of soybean (Glycine max L. cv. Kurosengoku) and sorghum (Sorghum bicolor Moench cv. Yukijirushi) on dry matter production, dinitrogen-fixing activity of soybean nodules and possible nitrogen transfer from soybean to sorghum at four spacing levels, namely 12.5 × 12.5 cm; 17.7 × 17.7 cm; 25 × 25 cm; and 50 × 50 cm. Dry matter production was consistently greater in mixed cropping than in mono-cropping, mainly due to the enhancement of sorghum growth regardless of spacing. Dinitrogen-fixing activity estimated by the acetylene reduction method in soybean decreased with the increase in the plant population density and with mixed cropping. Sorghum growth was closely related to the N accumulated in the plant. N-transfer from soybean was evident and was greatest at a 12.5 × 12.5 cm spacing. N-transfer from soybean to sorghum calculated on the assumption that there is no difference in the absorption ability of soil nitrogen between s...

Cell membrane stability and leaf water relations as affected by nitrogen nutrition under water stress in maize

Abstract A field experiment was conducted to investigate the effect of N nutrition under water stress conditions on the cell membrane stability (CMS) measured by the polyethylene glycol (PEG) test, plant water relations, and osmotic adjustment in maize (Zea mays L.). Stressed plants showed greater adaptations to water deficits at higher N levels. Leaf water potential and osmotic potential decreased, turgor potential increased, and CMS increased with increasing N levels. Osmoregulation was evident at higher N levels with sugar and K as the major osmotic contributors. Results suggest that osmoregulation is influenced by N nutrition.

Phosphorus fractions in relation to growth in pigeon pea (Cajanus cajan (L) Millsp.) at various levels of P supply.

Abstract In order to evaluate the tolerance of pigeon pea (Cajanus cajan (L) Millsp. ICPL 316) to low-P conditions in relation to the utilization of P among the major biochemical fractions, soybean (Glycine max (L) Merr cv. Tamahomare) was used as a reference crop. Pigeon pea and soybean were cultured hydro-ponically in a glasshouse for 28 days with three levels of orthophosphate (Pi). Low, control, and high-P plants were supplied with 0.1, 1.0, and 10 ppm P respectively. In another experiment, pigeon pea seedlings were grown in a solution culture for 48 days with four levels of Pi concentrations ranging from 0 to 30 ppm. Results of the two experiments indicated that pigeon pea requires relatively low concentrations of external Pi for growth compared to soybean Low-P treatment significantly reduced leaf area, leaf dry weight, and shoot weight in both species but the reduction was more pronounced in soybean than in pigeon pea. Low-P treatment did not significantly affect the root dry weight in both species...

Relationship between Water use Efficiency and Cuticular Wax Deposition in Warm Season Forage Crops Grown under Water Deficit Conditions

In order to clarify the relationship between water use efficiency (apparent photosynthetic rate/transpiration rate) and the synthesis and deposition of epicuticular wax and of lipids in leaf internal tissues in various forage crops with different drought tolerance, the contribution of cuticular wax to the leaf cuticular resistance to water loss under water stress was estimated. Under water stress conditions, the cuticular resistance of the drought tolerant plant Chloris gayana Kunth. increased about twofold compared with that of a well-watered plant, whereas the cuticular resistance of the sensitive plant Coix lacryma-jobi L. increased by about 10%. The amount of epicuticular wax deposited on the leaf surface in both plants increased by water stress. However, the amount in the tolerant plant was much higher than those in the sensitive one. Radioactivity of 14C incorporated into the leaf surface wax of stressed C. gayana and C. lacryma-jobi plants was 27 and 50% less than that of well-watered plants, respe...

Dinitrogen fixation, ureide concentration in xylem exudate and translocation of photosynthates in soybean as influenced by pod removal and defoliation

Abstract Effects of pod removal and defoliation on the growth, dinitrogen-fixing activity, ureide concentration in xylem exudate and nodules, and translocation of photosynthates in soybean (Glycine max (L.) Merr. cv. Tamahomare) were examined and the following results were obtained. 1. Dinitrogen-fixing activity decreased significantly by both pod removal and defoliation. 2. The concentration of sugars and starch in the nodules increased by pod removal but decreased by complete defoliation, while it did not change by partial defoliation. 3. The ureide concentration in the xylem exudate and nodules increased by pod removal, especially by complete defoliation. 4. Pod removal led to a decrease in the export rate of 14C from leaf but had no effect on 14C distribution percentage in the nodules. 5. Exudation rate of ureide-14C in the xylem sap was lower during the first hour after the exposure to 14CO2 and thereafter it was higher in depodded than in control plants. From these results, it is suggested that the ...

Dry matter production and dinitrogen fixation of wild and cultivated soybean varieties as affected by pod removal

Abstract A wild soybean variety (Glycine soja (L.) Sieb and Zucc cv. Nakei-No. 1, indeterminate type) and 2 soybean cultivars (Glycine max (L.) Merr. cv. Tamahomare and Harosoy 63, determinate and indeterminate types, respectively) were grown in pots. The two soybean cultivars were also grown in the field without an application of combined-N. The effect of pod removal on dry matter production and dinitrogen-fixing activities were determined. 1. The total dry weight of the control soybean cultivars increased markedly due to the increase of the pod weight during the experimental period, whereas the increase of the total dry weight in the wild soybean variety was lower. 2. Pod removal which resulted in the decrease of plant weight increment in the cultivar Tamahomare, did not affect plant weight increment in the wild soybean variety due to the large compensatory increase of leaf and stem weight. 3. Dinitrogen-fixing activity of Tamahomare decreased markedly by pod removal, whereas in Harosoy, the decrease wa...