Raafat K. Rabie

EFFECT OF NITRATE APPLICATION AND SHADE TREATMENT ON THE NITROGEN FIXATION AND YIELD OF SOYBEAN PLANT

Abstract Under sterilized-controlled conditions, soybean plant was grown with nitrate (N), Rhizobium inoculation (R), or nitrate and Rhizobium inoculation (N+R); under natural light or continuous shade conditions. Plant growth, respiration of root system, and yield were investigated in relation to nitrogen fixation. Nonnodulated plants (N) accumulated larger amount of dry matter as compared to (N+R) plants, and the opposite was found true at pod filling stage when the plants were exposed to natural light. R-plants were found to be the lowest in the accumulation of dry matter and the earliest in senescence. Nodule size and not nodule number, proved to be a good indicator for the nitrogen fixing activity. Nitrate suppressed both the size and specific activity of nodules. Specific respiratory activity of nodules was estimated to be up to three times as that of roots. Regarding seed yield, R-plants were the lowest and N-plants were the highest. (N+R) plants were the highest in the pod number per plant, while ...

EFFECT OF SALINITY AND MOISTURE CONTENT OF SOIL ON GROWTH, NUTRIENT UPTAKE AND YIELD OF WHEAT PLANT

A pot experiment was conducted to investigate the effect of salinity and moisture content of soil on growth, nutrient uptake, sodium-potassium relationship, and yield of wheat plant. Levels of soil salinity were adjusted to 0.18 (control), 0.3, 0.6, and 0.9% of oven dry soil. Levels of soil moisture were 40, 60, and 80% of capillary capacity. The following results were obtained. 1) Dry matter yield, uptake of N, P, and K as well as protein content in grains all increased at a soil salinity level of 0.3% and then decreased with increasing soil salinity up to the level of 0.9% which was severely depressive. However, the number of grains per spike, the weight of 1,000 grains and the efficiency of grain yield production percent all were generally decreased with each increase in soil salinity. 2). Dry matter yield as well as the uptake of N, P, K, and Na were increased when the soil moisture was 60% of the capillary capacity at the tillering stage and 60 to 80% at the booting and maturity stages. 3) Upon matur...

Effect of NaCl salinity on growth and distribution of sodium and some macronutrient elements in soybean plant

Abstract Two pot experiments were carried out with soybeans using vermiculite and water culture as growth media to study: a) the effect of NaCl salinity on the growth and cationic relations in the plant and b) the effect of NaCl elimination on the cationic relations in the salt-affected plants. The results obtained were as follows. 1. Salinity depressed the plant growth, particularly pods at the filling stage due to the low efficiency of pod yield production % (dry matter distribution %) in the salt-affected plants. 2. In the salt-affected plants, the stems were found to be the major sink of accumulated sodium, while the leaves exhibited the lowest Na concentration among the different plant parts. 3. After NaCl elimination from the growth medium, Na concentration in the salt-affected plants was markedly decreased particularly in the leaves and pods. In contrast, Na concentration in the shoots was slightly increased. 4. Salinity generally increased the concentrations of K, Ca, and Mg in the leaves and decr...

Uptake and distribution of combined nitrogen and its incorporation into seeds of nodulated soybean plants as revealed by 15N studies

Abstract Pot experiments were carried out with soybean plants grown in N-free solution and supplied with NO3 - or NH4 + before 15N administration, in order to study the uptake, distribution, and redistribution of absorbed nitrogen. To determine the utilization and incorporation of combined nitrogen in the seed yield, as influenced by the N form and application time, another series of experiments was conducted in which plants were grown in N-free solution before 15N feeding at pod setting (P.S.) or initial pod filling (I.P.F.), as 15NO3 - or 15NH4 +. By comparing the nitrate-treated plants (Nt-plant) with the ammonium ones (Am-plant), and P.S. with I.P.F., the following results were obtained. 1. Nt-plants accumulated higher amounts of dry matter in different plant parts, particularly the pods which proved to be an active sink for the newly metabolized nitrate nitrogen. 2. Both the 15N abundance and 15N incorporation in the whole plant were much higher for Nt-plants, and the same was true for different plan...

Effect of combined nitrogen on the distribution pattern of photosynthetic assimilates in nodulated soybean plant as revealed by 14c

Abstract A general relationship was found between combined nitrogen nutrition and translocation pattern of 14C assimilates in an experiment carried out in greenhouse with soybean plant grown in nitrogen-free water culture and supplied with 40 ppm N in the form of NO3 -or NH4 + for 1 week before exposure to 14CO2 at initial pod filling stage. The longest the cold chase time after 14CO2 exposure, the highest the percentage of total recovered 14C was translocated from the leaves to the different plant parts. Ammonium cecreased the capacity of leaves for exportation of labeled photosynthates. A relatively high percentage of total recovered 14C was observed in the stems and pods of NO3 --treated plants as compared to NH4 +-treated plants, and the opposite was true with root system. In different plant parts except nodules, nitrate-treated plants had high specific radioactivities and ammonium-treated plants had low specific radioactivities compared with control. Among the different plant parts other than leaves,...

Growth, nodule activity and yield of soybeans as affected by the form and application method of combined nitrogen

Abstract A pot experiment was conducted to investigate the effect of the form and application method of combined nitrogen on growth, nitrogen fixation and yield of soybean plant. Nitrate, ammonium, or urea was applied as surface, homogeneous, or deep application. Spraying technique was also used with urea. All treatments increased the dry matter accumulation in plant at initial flowering as well at initial pod filling. At pod filling, N treatments increased the number but not the weight of pods. Surface application of different nitrogen forms was the most promotive treatment on dry weight particularly with nitrate. Concerning the nodule dry weight, at initial pod filling, surface N applications had no depressive effect. At pod filling stage, surface application of nitrate was the most promotive treatment. Basal dressing of ammonium or urea was slightly promotive, while urea spray was repressive. Concerning the acetylene reducing activity of nodules, all N treatments were almost repressive on both total an...

EFFECT OF SALINIZATION AND DESALINIZATION ON THE UPTAKE, DISTRIBUTION, AND ASSIMILATION OF FERTILIZER NITROGEN BY NODULATED SOYBEANS

Abstract Soybean plants were grown in water culture, to study the effect of salinization and desalinization on the uptake, distribution, and assimilation of fertilizer nitrogen using 15N as a tracer. The following results were obtained: 1. Up to 8 days after NaCl application, 15N uptake by the salt-affected plants was lower than that by the control plants, but higher after NaCl removal. 2. During the time course of 16N absorption, the incorporation of 15N into the leaves was depressed by salinization, even after NaCl removal. On the other hand, the nodulated roots of the salt-affected plants accumulated higher amounts of 16N than the control plants, even after NaCl removal. Pods and stem followed the general trend of the whole plant. 3. The proportion of absorbed 15N in the pods which decreased by salinization, was similar to that of the control plants at the end of the desalinization period. An opposite trend was observed for the nodulated roots. 4. Assimilation of fertilizer 15N into the various nitroge...

EFFECT OF SALT STRESS ON NITROGEN NUTRITION AND YIELD QUALITY OF NODULATED SOYBEANS

Abstract A pot experiment was carried out with soybean plants using vermiculite as a growth medium to study the effect of salt stress on: a) the uptake and distribution of biologically fixed nitrogen and applied fertilizer nitrogen using 15N as a tracer and b) the contents of protein, free amino acids, sugars, and starch in pods as criteria of yield quality. The results obtained are summarized as follows: 1. Salt-affected plants derived lower amounts of atmospheric nitrogen (NDFA), and also absorbed lower amounts of fertilizer nitrogen (NDFF) per plant as compared to control plants. 2. The percentage of nitrogen derived from fertilizer (NDFF %) in the salt-affected plants was higher than in the control plants, suggesting that the salt-affected plants are less dependent on fixed nitrogen due to their lower nodulation ability. 3. Nodules as compared to other plant organs were much less dependent on fertilizer nitrogen. This was more evident in the control plants compared to the salt-affected ones. 4. Regard...

Effect of application time of labeled combined nitrogen on its absorption and assimilation by nodulated soybeans.

Abstract Soybean plants were grown in N free nutrient solution. At the pod setting (P.S.) or initial pod filling (I.P.F.) stage, plants were fed with 15NO3 (Nt-plants) or 15NH4 + (Am-plants) in order to investigate the utility of nitrogen top dressing. P.S. and I.P.F. as well Nt. and Am-plants were compared. The absorption and incorporation of combined nitrogen in the ethanol soluble and insoluble fractions of different plant parts were higher at P.S., particularly with the nitrate form. Among the different plant parts, pods represented the biggest sink of combined nitrogen at both P.S. and I.P.F. Both Nt- and Am-plants showed almost the same pattern in the percentage distribution of combined nitrogen in the ethanol soluble and insoluble fractions of pods. The distribution percent of combined nitrogen in the upper leaves was higher than that in the lower leaves, particularly in the ethanol soluble fraction in Nt-plants and the insoluble fraction in Amplants. In stems, roots and nodules, the distribution p...

EFFECT OF SODIUM CHLORIDE AND NITRATE ON DRY MATTER PRODUCTION AND MICRONUTRIENT CONTENT OF WHEAT PLANT

A sand culture experiment was conducted using four wheat varieties viz. Sakha 8 (V1), Sonalika (V2), Sakha 3 (V3) and Soltane (V4). Plants were irrigated with nutrient solutions containing three levels of salinity viz. 0 (S1), 44 (S2), and 88 (S2) meq NaCl/liter, and three levels of nitrate viz. 3 (N1, 6 (N2), and 9 (N3) meq NO3 1/liter. Plants were sampled at early spike emergence for measurement of dry matter and contents of Fe, Mn, and Zn. The results are summarized as follows. 1) The efficiency of spike dry matter production percent was promoted by increasing salinity, though, the opposite was observed for the dry matter yield of shoots and spikes. 2) The higher the nitrate level the higher was the dry matter yield per plant and the efficiency of spike dry matter yield production percent as well. 3) Tolerance of the tested wheat varieties to sodium chloride followed the order; V1 < V2 < V3 < V4 and the critical osmotic pressures of sodium chloride, for 50% reduction in dry matter yield, could be predi...