Shoot Dry Matter Yield Research Articles

YIELD AND YIELD COMPONENTS OF UPLAND RICE AS INFLUENCED BY NITROGEN SOURCES

Ammonium sulfate and urea are main sources of nitrogen (N) for annual crop production in developing countries. Two greenhouse experiments were conducted using ammonium sulfate and urea as N sources for upland rice grown on a Brazilian Oxisol. The N rates used were 0, 50, 100, 150, 3000, and 400 kg N kg−1 of soil. Yield and yield components were significantly increased in a quadratic fashion with increasing N rate. Ammonium sulfate X urea interaction was significant for grain yield, shoot dry matter yield, panicle number, plant height and root dry weight, indicating a different response magnitude of these plant parameters to two sources of N. Based on regression equation, maximum grain yield was achieved with the application of 380 mg N kg−1 by ammonium sulfate and 271 mg N kg−1 by urea. Grain yield and yield components were reduced at higher rates of urea (>300 mg kg N) but these plant parameters’ responses to ammonium sulfate at higher rates was constant. In the intermediate N rate range (125 to 275 mg kg−1), urea was slightly better compared to ammonium sulfate for grain yield. Grain yield was significantly related with plant height, shoot dry weight, panicle number, grain harvest index and root dry weight. Hence, improving these plant characteristics by using appropriate soil and plant management practices can improve upland rice yield.

Effect of cadmium-contaminated soils on dry matter yield and mineral composition of raya (Brassica juncea) and spinach (Spinacia oleracea)

Raya (Brassica juncea) and spinach (Spinacia oleracea), grown as leafy vegetables, are known to accumulate large amounts of heavy metals in their shoots and roots because of their high biomass and root proliferation. In a pot experiment, a sandy loam soil was polluted with cadmium (Cd) at rates of 0, 5, 10, 20, 40 and 80 mg kg−1 soil to assess the accumulation pattern and its effect on the dry matter yield and mineral composition of these vegetables. There was a decrease in dry matter yield due to the phytotoxic effect of Cd. The rate of Cd application at which a significant decline in root and shoot dry matter yield occurred varied depending on the vegetable. It was 20 mg Cd kg−1 soil in the shoots for both crops. However, the roots of raya were found to be more tolerant of Cd toxicity than those of spinach, as is evident from the fact that a significant decline in dry matter yield occurred at 20 and 10 mg Cd kg−1 soil, respectively. Since no visual toxic symptoms were observed on the leaves of raya in any of the treatments, it is clear that the metal may accumulate in this vegetable without visual evidence of its presence. However, at application levels beyond 40 mg kg−1 soil, toxicity symptoms, in the form of interveinal chlorosis of the leaf lamina followed by necrosis and leaf rolling, were clearly evident in the case of spinach. The reduction in root and shoot growth corresponded with the amounts of extractable Cd in the soils. The total content of Cd in the crops increased gradually as the rate of applied Cd rose and the roots accumulated much higher amounts than the shoots. The relationship of Cd with Zn and Fe was synergistic in both roots and shoots at the lower rates, but antagonistic at higher Cd application rates for both the crops, while in the case of Mn and Cu, the relationship was negative and antagonistic.

Recovery of degraded pasture in Rondônia: macronutrients and productivity of brachiaria brizantha

Pasture is the main form of land use in Amazonia. Over time the pasture grass loses vigor and yields decrease, indicating a certain degree of degeneration. The main causes of degradation are lack of pasture maintenance and subsequent weed infestation, the choice of regionally unsuitable forage species and excessive grazing. The main purpose of this study was to evaluate the impact of different recovery managements on soil chemical properties and grass yield of a degraded pasture in Rondônia. For this purpose, an experiment was installed in October 2001, consisting of five treatments: C = control; HA = harrowing + NPK + micronutrients; HE = Herbicide + NK + micronutrients; R = No-tillage rice + NPK + micronutrients; and S = No-tillage soybean + PK + micronutrients. The following N, P and K sources were used: ammonium sulfate for N, calcined phosphate for P and potassium chloride for K. The experiment was arranged in a randomized block design with four replications. The shoot dry matter yield of the grass was analyzed as of the 35th month of experimentation, in a dry and a rainy period. Phosphorus fertilization resulted in significant increases in Ca2+ and Mg2+ and increasing trend of P in the topsoil in the initial months of the experiment in treatments HA and S and increases in Ca2+ and P (trend) in the treatment R. The cumulative production of Brachiaria brizantha, from Sep/2004 to Mar/2005, was 30,025, 28,267 and 27,735 kg ha-1 shoot dry matter in the treatments HA, R and S, respectively. These values differed significantly from treatments C and HE, with 17,040 and 17,057 kg ha-1, respectively. It was concluded that phosphorus fertilization associated to pasture reform was effective to raise the dry matter yield of Brachiaria brizantha. Rice or soybean under no-tillage is recommended as a practice of pasture recovery, due to the residual effect of fertilization.

ROOT ZONE TEMPERATURE INFLUENCES ZINC REQUIREMENT OF MAIZE CULTIVARS ON A CALCAREOUS LOAM SOIL

The zinc (Zn) requirement of a maize (Zea mays L.) hybrid (‘FHY-396’) and an indigenous variety (‘EV-7004’) was measured at low (22.4 ± 5°C) and high (28.8 ± 5°C) root-zone temperatures (RZT). Four Zn rates (0, 3, 9 and 27 mg kg−1 soil) were applied to a calcareous loam soil in pots for the glasshouse study. Shoot and root dry matter yields were significantly more at the higher RZT. Regardless the RZT, maximum relative shoot dry matter yield in hybrid and variety was produced, respectively, at 9 and 3 mg Zn kg−1 soil. Zinc concentration in roots and shoots of both the cultivars increased with Zn rates and it was significantly more at the higher RZT. Cultivars differed in critical Zn concentration (CZnC) required for maximum shoot dry matter yield. The CZnC ranged from 25 to 39 μg Zn g−1 plant tissue for optimum growth of both the cultivars at low and high RZT.

GROWTH AND IRON-MANGANESE RELATIONSHIPS IN DRY BEAN AS AFFECTED BY FOLIAR AND SOIL APPLICATIONS OF IRON AND MANGANESE IN A CALCAREOUS SOIL

Manganese (Mn) deficiency may be induced by adding large quantities of iron (Fe), provided that soil manganese is marginally deficient. Results of a greenhouse study showed that iron soil application did not influence shoot dry matter yield of dry bean due to the fact that the iron:manganese ratio in aerial parts of dry bean was higher than 0.4. A foliar spray of 2% iron sulfate significantly reduced it probably due to the high level of shoot iron and iron:manganese ratio greater than 4. Iron application decreased concentration/uptake of shoot manganese due to the iron-manganese antagonistic relationships. Mangenese soil application is not an effective method in correction of manganese deficiency induced by iron fertilizers. Iron did not affect root manganese uptake, indicating that manganese absorption was not affected by iron application. Both manganese/iron soil tests are recommended in calcareous soils with manganese soil test in marginal range.

Effects of phosphate rock application on dry matter yield and phosphorus recovery of maize and cowpea grown in sequence

The study was conducted in a greenhouse at the Institute of Agricultural Research and Training (IAR & T) Ibadan, Nigeria to evaluate the influence of P source, rate and frequency on dry matter yield of maize and cowpea grown sequentially in three soil types. Three sources of P: Ogun phosphate rock (OPR: 20.2% P2O5); Crystallizer super (CS: 31.4% P2O5) and Single super phosphate (SSP: 18.0% P2O5); Four rates (0, 20, 40 and 60 kg/ha P2O5) and Two frequencies (regular and alternate application) were studied on three soil types (Ilora-Udipsamment; Ibadan- Arenic Haplustalf and Epe - Aquic Arenic Haplustalf soils). The experiment was laid out in a split-split plot arrangement, using completely randomized design. Phosphate application significantly enhanced dry matter yields of maize and cowpea. Single super phosphate (SSP) gave ahigher total biomass than the phosphate rocks (PR). On Ilora soil with the regular application frequency in the first cropping, maize total biomass was increased by SSP from 4.23 g/plant to 8.20, 9.25 and 9.72 with 20, 40 and 60 kgP/ha while it was increased to 6.78, 6.26 and 6.34 g with OPR but to 6.88, 7.60 and 7.15 g with CS. Cowpea yields were increased from 2.12 g/plant to 3.28, 4.04 and 3.36 g with SSP; to 3.34, 3.27 and 2.61 with CS and to 2.59, 2.78 and 2.39 g with OPR. On Ibadan soil, maize biomass yield ranged between 6.13 and 6.37 g with OPR; between 7.22 and 7.56 with CS and between 6.80 and 10.45 g with SSP. Cowpea yields were between 6.54 and 7.81 with OPR; between 5.70 and 6.80 with CS and were between 6.59 and 8.94 with SSP. Both Ogun and crystallizer super PRs gave comparable dry matter yields of maize and cowpea as single super phosphate. Best growth performance was observed with application of 60 kg/ha in all the soils. Significant treatment effects in shoot, root and total dry matter yields of maize and cowpea were obtained with 60 kg P/ha. Alternating maize with cowpea gave a higher total plant biomass than continuous maize. Regular frequency of application was superior to alternate frequency of application. Cumulative apparent P recovery of maize and cowpea at the end of final cropping was maximal with 20 kgP/ ha SSP in the three soils. It had 75, 80 and 70% recoveries for Ilora, Ibadan and Epe soils respectively. Key words: Phosphorus sources, recovery, corn, dry matter yield

Interaction effect of tree leaf litter, manure and inorganic fertilizer on the performance of maize in Zimbabwe

An experiment was conducted over two seasons to evaluate the effects of 5 t ha-1 of different organic inputs (manure, Brachystegia spiciformis (miombo) leaf litter, Leucaena leucocephala senesced leaves) and Compound D (8N-14P-7K) fertilizer (300 kg ha-1), and their combinations on maize growth and yield on a sandy soil at Makoholi Experimental Station, Zimbabwe. Prior to planting, vegetation from a 12 year fallow (primarily annual grasses) was ploughed under in November 1990. Maize ( Zea mays ) hybrid (R201) was planted in both seasons. Yields were extremely high in the first season. Addition of L.leucocephala leaf litter and manure to the soil, depressed plant growth up to tasselling and silking of maize, respectively. Leuceana leucocephala leaf litter resulted in a decrease in both shoot dry matter and grain yields. Total above ground dry matter was highest from the fertilizer only and the fertilizer plus miombo litter treatments, though both treatments were not significantly different from the control. Application of both manure and miomba litter resulted in suppression of growth compared to the control. Application of both manure and miombo litter resulted in suppression of growth compared to the control. Suppression of growth was overcome by the application of Compound D fertilizer. In the absence of fertilizer, there was no difference between manure and miombo litter, but miombo litter preformed better than manure in the presence of fertilizer. It is hypothesized that the application of Leucaena, manure and miombo litter resulted in immobilization of nutrients. Leucaena, which is rich in N but low in P, probably resulted in P immobilization.

Effect of phosphorus nutrition on growth of potato genotypes with contrasting phosphorus effeciency

Potato (Solanum tuberosum L.) has high phosphorus requirement for optimum growth and yield. Thus, under P deficiency, growth and yield are considerably reduced. An experiment was conducted in a controlled growth chamber on the effect of P supply on morphological and physiological plant parameters of three potato genotypeshaving contrasting P efficiency. The genotypes were CGN 17903, CIP 384321.3 and CGN 18233. They were grown under two P levels [100 mg P kg-1 soil (low P) and 700 mg P kg-1 of soil (high P)]. Treatments were arranged in a completely randomised block designs with six replications. Low P supply reduced shoot dry matter yield, relative growth rate, leaf number, whole plant relative leaf expansion rate, total leaf area per plant, plant height and net assimilation rate of P-inefficient genotype, more than that of the P-efficient genotypes. However,low P supply did not affect net photosynthetic rate per unit leaf area, leaf dark respiration rate, chlorophyll fluorescence rate and electron transport rate of both P-efficient and inefficient genotypes. P-efficient genotype CGN 17903 allocated more dry matter yield to the leaf which might have enabled higher light harvesting, hence contributing to high biomass accumulation of this genotype.

Soil-applied silicon decreases severity of wheat spot blotch on silicon-deficient soils

Spot bloth caused by Bipolaris sorokiniana is an important wheat desease mainly in hot and humid regions. The aim of this study was to evaluate the response of wheat to different sources and modes of Si application, as related to the severity of wheat spot blotch and plant growth, in two Si-deficient Latosols (Oxisols). An greenhouse experiment was arranged in a 2 x 5 factorial completely randomized design, with eight replications. The treatments consisted of two soils (Yellow Latosol and Red Latosol) and five Si supply modes (no Si application; Si applied as calcium silicate and monosilicic acid to the soil; and Si applied as potassium silicate or monosilicic acid to wheat leaves). No significant differences were observed between the two soils. When Si was applied to the soil, regardless the Si source, the disease incubation period, the shoot dry matter yield and the Si content in leaves were greater. Additionally, the final spot blotch severity was lower and the area under the spot blotch disease progress curve and the leaf insertion angle in the plant were smaller. Results of Si foliar application were similar to those observed in the control plants.

Effects of Terralyt - Plus on soil pH, nutrient uptake and dry matter yield of maize

Acid soils are common in the tropics and managing them for sustainable cropping usually demands soil amendments. A greenhouse experiment was conducted at the Institute of Agricultural Research and Training, Ibadan, Nigeria to evaluate the effects of a soil amendment substance - organic biostimulator - Terralyt-Plus® on the growth, soil pH, nutrient uptake and dry matter production of maize. The soils used for the study (Entisol, Alfisol) were collected from the coastal and forest zones of Nigeria. The Terralyt-Plus® was applied (0, 20, 40 and 60 ml m-2) with the conventional urea, single super phosphate and muriate of potash fertilizers. These were compared with a no-fertilizer control. The experiment was laid out with completely randomised design (CRD) replicated three times. Maize was grown for six weeks when the shoot and roots were harvested for dry matter yield assessment and determination of selected chemical constitutuents. Complementing inorganic fertilizer application with Terralyt-Plus® significantly improved maize performance on the soils. Shoot dry matter yield increased from 15 - 32% compared with sole inorganic fertilizer treatment. It was 64 -77% over the control. Phosphorus uptake was highest at 40 ml m-2 on the soil at Ilora while for soils at Ikenne and Badagry; it was at 20 ml m-2. Application of 20 - 40 ml m-2 (200 - 400 l ha-1) gave optimum height and dry matter yield of maize, and improved nutrient uptake of maize pla

Corretivos da acidez do solo e níveis de umidade no desenvolvimento da cana-de-açúcar

Sugar caner (Saccharum spp.) cultivation is quite disseminated throughout Brazilian territory due to its easy cultivation and its multiple uses such as  sugar and alcohol yield and animal feeding. In order to have a satisfactory yield, the combination of factors such as humidity and soil acidity correction should be corrected. This work had the objective of evaluating use of correctives (limestone and slag) in three levels of soil humidity, dry matter yield of shoot, culm, root and culm number of plant. Five levels of limestone and metallurgy slag corrective were evaluated, so that saturation by bases (V%)  remained after incubation with: N1 (control, V = 21.4%), N2 (V = 40%); N3 (V = 60%); N4 (V = 80%) and N5 (V = 100%). Incubation was carried out in plastic sacks for 21 days, with humidity close to 70%. After 150 days of cultivation, counting of culm (CC) and cut of shoot were carried out by separating culm from leaves, determining dry matter of shoot (DMAP), dry matter of leaf (DML), dry matter of culm (DMC) dry matter of root (DMR). Usage of soil acidity correctives, level of water and level of saturation by bases influenced the development and mineral nutrition of sugar cane. Slag yield greater production of dry matter of shoot of sugar cane in relation to limestone for the lowest levels of water in soil (60 and 80%CC). Increase of saturation by bases with appliance of increasing doses of limestone and slag increased yield of aerial, leaves, stem and roots dry matter of sugar cane.

INFLUENCES OF N AND S INTERACTION ON GROWTH AND PUNGENCY OF CHINESE BUNCHING ONION (ALLIUM FISTULOSUM L.)

Allium species are grown worldwide because of their commercial, nutritional and health value. To seek a high yield and gain much income, farmers apply a large quantity of fertilizer, especially N, which may increase the yield at the cost of quality. A pot experiment was carried out to investigate the growth and pungency (replaced by the enzymatically formed pyruvic acid (EPY)) of Chinese bunching onion (Allium fistulosum L.) as affected by N and S interaction, three levels of N and S were designed as 2, 6, 12 mM and 0.1, 2, 4 mM respectively in solutions of deionized water. Plants were grown in a waterproof place for 15 weeks and then harvested. Results indicated that plant growth and shoot dry matter yield were significantly affected by added N but not by S. Shoot dry weight increased with increasing N supply. Compared to the high N level (12 mM), S nutrition did not increase the shoot EPY content at the other two N levels, but the soluble solids contents (SSC) were relatively higher. Meanwhile, N may promote EPY synthesis and increase total EPY content, especially at a large application quantity. In addition, total N contents of root and shoot were affected significantly by added N but not by S. Total shoot S content had a significant correlation with the EPY content. As a consequence of this study it could be concluded that N nutrition could promote the plant growth, while S nutrition could increase the pungency of Allium species, most important of all, S application could promote total EPY content at a higher N supply rate.

PHOSPHORUS-MOLYBDENUM RELATIONSHIP IN SOIL AND RED CLOVER (Trifolium pratense L.) ON AN ACID ANDISOL

We studied the phosphorous (P) and molybdenum (Mo) relationship in soil and red clover (Trifoliumpratense L.) in a non limed and limed acid Andisol of Southern Chile. In soil, we evaluated the effect of different liming (0 and 2000 mg kg-1), P (0, 200 and 400 mg kg-1), and Mo (0, 0.58 and 0.96 mg kg-1) doses supply on soil available Mo. In addition, the availability of P and Calcium (Ca) in treated soils was determinated. In red clover, we studied the Mo and P shoot concentrations and dry matter yield in response to the different treatments applied to the soil. Also, we measured the changes produced by Mo uptake in shoot Cu concentrations. The results showed that both, lime and more strongly P and Mo additions significantly (P ≥ 0.05) increased soil Mo availability. In contrast, soil available P was not significantly (P ≥0.05) affected by liming and Mo treatments. A significant high correlation (r = 0.579, at P ≥ 0.05) was observed among soil Mo availability and shoot Mo concentrations, as well as between soil available P and shoot concentration of P (r = 0.844, at P ≥ 0.01). In this study for all fertilization treatments, shoot Cu concentrations reached values which are considered as normal for forage species. We also shown that the simultaneous applications of high P and Mo rates could be produce red clover shoot Cu/Mo ratios that should provoke Mo-induced Cu deficiency (Molybdenosis) for the cattle. Red clover yield was no significantly different in limed and non limed soils. Nevertheless, red clover yield production increased at increasing rates of P and Mo in both, non limed and limed soil. The major practical implication of these results is that the application of Mo doses equal or superior to 200 g ha-1 to acid Andisols, are recommendable to obtain appropriate Mo shoot content on red clover. In addition, our results shown that P supply to these soils, rather than liming, is necessary to obtain sufficient values of shoot Mo concentrations in red clover.

Phytoremediation of lead by jack beans on a Rhodic Hapludox amended with EDTA

A greenhouse study was conducted to evaluate the effects of ethylenediamine tetraacetic acid (EDTA) addition to soils on the lead (Pb) phytoextraction potential of jack beans (Canavalia ensiformis L.). In a pot experimentSoil samples (dystrophic Rhodic Hapludox) were treated with six Pb rates (0, 100, 200, 350, 1,200, and 2,400 mg kg-1 soil) applied as Pb(NO3)2 without and with EDTA application (0 and 0.5 g kg-1, respectively). Lead, Cl-, NO3-, NH4+, SO4(2-), H2PO4-, Zn2+, Cu2+, Fe3+, Al3+, Ca2+, Mg2+, K+ and DOC (dissolved organic carbon) concentrations obtained in a saturation soil extract (soil:water ratio of 1:0.3) were used for Pb speciation by means of the software Visual-Minteq 2.30. Soil Pb-availability was assessed with Diethylene triamine pentaacetic acid (DTPA) extraction. EDTA treated soils showed higher Pb (as PbEDTA2-), and Fe (as FeEDTA-) concentrations in soil solution leading to higher uptake of these elements by the jack bean. On the other hand, it decreased the concentration of stable complexes as Pb-DOC and Fe-DOC. EDTA also induced better nutrition to plants building up the concentration of non target metals (Ca, K, Mg, Zn, Cu, Fe and Mn) in shoots. Shoot dry matter yield remained constant even at the highest Pb rates after EDTA treatment. Jack bean can be considered as a potential Pb-phytoextractor. In addition, the DTPA solution was effective to assess Pb availability to the plants at all applied Pb rates.

Mechanism of Salinity Tolerance in Selected Wheat (Triticum aestivum L.) Cultivars

An experiment in NaCl solution culture was conducted to observe the mechanism of salinity tolerance in selected three wheat (Triticum aestivum L.) cultivars, [BWIR7 (Mexico), Gutha (Australian) and KRL19 (Indian)] differing in salinity tolerance. Fifteen days old seedlings of each cultivar grown in half strength Hoagland nutrient solution were subjected to incremental salt stress until the required salinity levels (0, 180-mol m-3) were obtained. Dry matter yield (DMY) at 30 days, indole acetic acid (IAA), abscisic acid (ABA) and total free amino acid (AA) contents of leaves/root at 29 days and dehydrogenase activity of roots at 34 days were determined after initiation of the salinity stress. Shoot and root weight (DMY), dehydrogenase of root and IAA contents both in leaves and root of all the cultivars decreased whereas, ABA and AA contents increased. At saline treatment, cultivar, KRL19 produced maximum shoot DMY and BWIR7 minimum. Whereas, in case of roots Gutha produced maximum and KRL 19 minimum DMY. Dehydrogenase activity of root BWIR7 was more affected followed by Gutha and KRL19. The extent of decrease of IAA content in leaves and roots of Gutha was more pronounced than the other cultivars. Increase in ABA contents of shoots and roots were more in KRL 19 followed by BWIR7 and Gutha respectively. The extent of increase of AA contents was more in the leaves of KRL 19. From this study, it was concluded that cultivar KRL 19 has the salinity inclusion and Gutha salinity exclusion mechanism. The salinity tolerance cultivars were in order of KRL 19 > Gutha> BWIR7

Aplicação de calcário com diferentes graus de reatividade: alterações químicas no solo cultivado com milho

Com a correção da acidez, nutrientes importantes para o cultivo do milho tornam-se mais disponíveis à planta, promovendo o aumento de produtividade. Objetivou-se com este estudo avaliar as alterações químicas ocorrentes em dois solos e na produção de matéria seca de milho pela aplicação de corretivos com diferentes graus de reatividade. Foi realizado um primeiro experimento em casa de vegetação, aplicando-se doses de três calcários comerciais, sendo um com reatividade média, denominado A (RE = 85,7 %; PRNT = 88,3 %), outro com reatividade baixa denominado B (RE = 83,7 %; PRNT = 76,2 %), e outro, denominado C (RE = 99,1 %; PRNT = 105,3 %) altamente reativo, em quatro cultivos sucessivos de milho. Os solos utilizados foram Neossolo Quartzarênico e Latossolo Vermelho. Os tratamentos foram dispostos inteiramente ao acaso, com quatro repetições, constando de três doses de calcário, calculadas para elevar a saturação por bases para 40, 60 e 80 %, além da testemunha. Paralelamente, um experimento de incubação foi realizado para verificar o efeito residual dos corretivos ao longo do tempo. A calagem aumentou os valores de pH, Ca2+ e Mg2+ e reduziu os teores de Al3+ trocável. O melhor crescimento do milho foi observado no Latossolo Vermelho. Neste solo, os calcários A e B foram mais eficientes na elevação do pH durante os quatro cultivos, enquanto o produto C teve menor eficiência na redução do Al3+ nos últimos ciclos, devido à sua maior reatividade. Os calcários A e C tiveram comportamentos semelhantes nos dois solos estudados. Houve queda na produção de matéria seca aérea com os cultivos sucessivos de milho. No experimento de incubação, os teores de Ca trocável foram maiores que os residuais.

Symbiotic N2 fixation in 30 field-grown cowpea (Vigna unguiculata L. Walp.) genotypes in the Upper West Region of Ghana measured using 15N natural abundance

In this study, 30 cowpea genotypes were assessed for symbiotic N2 fixation in 2005, and 15 of them were re-evaluated in 2006 using the 15N natural abundance technique. Shoot dry matter yield of cowpea genotypes increased significantly in cvs. Vuli-1, Glenda, IT93K-2045-29, IT90K-59, Omondaw, Apagbaala, and IT84S-2246 in 2005 producing about 3.0 to 3.6-fold more biomass relative to cv. Vallenga. In 2006, seven out of the 15 cowpea genotypes tested (namely, IT97K-499-39, TVu11424, Botswana White, IT84S-2246, Sanzie, Brown Eye, and Glenda) also produced more dry matter than cv. CH14. Shoot δ15N values ranged from −0.58‰ to 1.49‰ in 2005, and −1.51‰ to 1.40‰ in 2006, and these resulted in %Ndfa values of 63.5–86.7% and 56.2–96.3%, respectively. The amount of N-fixed was 49–178 kg N ha−1 in 2005 and 62–198 kg N ha−1 in 2006. Furthermore, there was a direct relationship between the level of symbiotic N nutrition and plant growth, and between grain yield and amount of N-fixed in 2005 and 2006. As a result, genotypes that fixed the most N also produced the largest biomass and the greatest amount of grain yield. The observed relationship between N2 fixation and biomass confirmed our view that cowpea (and other grain legumes) can be concurrently selected for higher N2 fixation, superior plant growth, and greater grain yield. The high levels of N-fixed by many of the cowpea genotypes in this study suggest that they can contribute large amounts of N to cropping systems in African agriculture.

Nitrogen Uptake and Its Association with Grain Yield in Lowland Rice Genotypes

ABSTRACT Nitrogen is one of the most yield–limiting nutrients in lowland rice in Brazil. A field experiment was conducted for two consecutive years to evaluate nitrogen (N) uptake by five lowland rice genotypes and its association with grain yield. The nitrogen rate used was 0, 50, 100, 150, and 200 kg ha−1. The genotypes evaluated were CNAi 8886, CNAi 8569, BRSGO Guará, BRS Jaburu, and BRS Biguá. Grain yield and dry matter yield of shoot were significantly influenced by N rate. However, response varied from genotypes to genotypes. Genotype BRSGO Guará, BRS Bigua, and BRS Jaburu were having linear response, whereas genotypes CNAi 8886 and CNAi 8569 were having quadratic response with the N application rate in the range of 0 to 200 kg ha−1. Overall, genotypes BRSGO Guará and CNAi 8886 were the best because they produced higher yield at low as well as at higher N rates. Nitrogen uptake in shoot was having quadratic relationship with grain yield, whereas nitrogen uptake in the grain was linearly associated with grain yield.

Genotypic variation of potato for phosphorus efficiency and quantification of phosphorus uptake with respect to root characteristics

AbstractPotato (Solanum tuberosum L.), an important food crop, generally requires a high amount of phosphate fertilizer for optimum growth and yield. One option to reduce the need of fertilizer is the use of P‐efficient genotypes. Two efficient and two inefficient genotypes were investigated for P‐efficiency mechanisms. The contribution of root traits to P uptake was quantified using a mechanistic simulation model.For all genotypes, high P supply increased the relative growth rate of shoot, shoot P concentration, and P‐uptake rate of roots but decreased root‐to‐shoot ratio, root‐hair length, and P‐utilization efficiency. Genotypes CGN 17903 and CIP 384321.3 were clearly superior to genotypes CGN 22367 and CGN 18233 in terms of shoot–dry matter yield and relative shoot‐growth rate at low P supply, and therefore can be considered as P‐efficient. Phosphorus efficiency of genotype CGN 17903 was related to higher P‐utilization efficiency and that of CIP 384321.3 to both higher P‐uptake efficiency in terms of root‐to‐shoot ratio and intermediate P‐utilization efficiency. Phosphorus‐efficient genotypes exhibited longer root hairs compared to inefficient genotypes at both P levels. However, this did not significantly affect the uptake rate and the extension of the depletion zone around roots. The P inefficiency of CGN 18233 was related to low P‐utilization efficiency and that of CGN 22367 to a combination of low P uptake and intermediate P‐utilization efficiency. Simulation of P uptake revealed that no other P‐mobilization mechanism was involved since predicted uptake approximated observed uptake indicating that the processes involved in P transport and morphological root characterstics affecting P uptake are well described.

Growth and Phosphorus Uptake of Three Riparian Grass Species

Riparian buffers can significantly reduce sediment‐bound P entering surface water, but control of dissolved P inputs is more challenging. Because plant roots remove P from soil solution, it follows that plant uptake can reduce dissolved P losses. We evaluated P uptake of smooth bromegrass (Bromus inermis Leyss.), reed canarygrass (Phalaris arundinacea L.), and switchgrass (Panicum virgatum L.) grown in a flowing nutrient solution culture system with P concentrations of 1 or 100 μmol L−1 Plants were destructively sampled at approximately 0, 26, 40, and 53 days after transplanting (DAT). In a separate, concurrent experiment, we simulated the effect of an inflow of runoff with low or high dissolved P by switching a subset of pots approximately 40 DAT. When grown in 1 μmol L−1 P solution, shoot dry matter (DM) yield increased in the order bromegrass < switchgrass < canarygrass. When grown in 100 μmol L−1 P solution, shoot DM yield increased in the order bromegrass = canarygrass < switchgrass. Shoot P content was correlated with shoot DM yield; however, switchgrass was the only species that had higher P content in plants grown in 100 μmol L−1 P solution than in 1 μmol L−1 P solution. When solution P concentration was abruptly increased or decreased, P uptake was affected more than plant growth. Shoot P concentration of canarygrass increased more than 3.5‐fold when the plants were switched from 1 μmol L−1 P solution to 100 μmol L−1 P solution. Shoot P concentration of switchgrass followed the same trend. The results of this solution‐culture experiment suggest that canarygrass and switchgrass would more effectively deplete dissolved P than would bromegrass.