Anthony Egrinya Eneji

UREA AND MANURE EFFECT ON GROWTH AND MINERAL CONTENTS OF MAIZE UNDER SALINE CONDITIONS

Salinity and soil nutrient deficiencies are the main factors reducing plant productivity in arid and semiarid areas. Among the essential elements, nitrogen is usually the most growth limiting plant nutrient in saline or non-saline soils. A pot experiment was carried out in the greenhouse to evaluate the influence of composted manure and urea as nitrogen sources on growth and mineral [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na)] content of maize (Zea mays L.) under different levels of salinity. Saline soils were prepared from an infertile loamy-sand soil, namely masatsuchi, by adding a mixture of Ca, Mg, and Na salt solutions with concentrations of 60, 110, and 160 mmolc L−1. The final salinity levels (ECe) achieved were 4, 9, and 13 dSm−1 denoted as S1, S2, S3, respectively; S0 denotes untreated soil. The pH of the saline soils ranged from 7.1 to 7.4. Nitrogen was applied at four levels as follows: urea, composted manure, ½ urea + ½ composted manure, and a control (no N fertilizer). Each of the three levels of applied N was at the rate of 200 kg ha−1. A basal dose of P and K was also applied. Treatments were factorially combined using RCB design with 3 replications. Maize was grown as the test crop. Plant growth and shoot and root biomass were monitored for 8 weeks, and shoot samples were also analyzed for N, P, K, Ca, Mg, and Na. Maize height and dry matter production were depressed with increasing salinity levels. The application of composted manure and urea fertilizer enhanced plant growth and nutrient uptake compared with the non-treated control. Maize growth was better under urea fertilizer than under composted manure. The uptake of nutrient was also affected by the salinity and form of fertilizer applied. Calcium, Mg, and Na uptake of shoot increased with increasing level of salinity irrespective of fertilizer level. However, for any level of salinity, the uptake of these elements differed in the following order: urea > urea + manure > composted manure > control. Nitrogen uptake decreased with increasing salinity up to S2 while P and K decreased up to S3. Irrespective of salinity, N, P, and K uptake were higher in urea and urea + manure treatments as compared to manure and control. The poor response of composted manure may be due to its short-term application or impeded N mineralization under saline conditions.

WHEAT RESPONSE TO NITROGEN SOURCE UNDER SALINE CONDITIONS

ABSTRACT The influence of nitrogen (N) sources on biomass yield and nutrient uptake of wheat (Triticum aestivum L.) under saline conditions was studied in a greenhouse experiment. Six different forms of N {nitrate-N as Ca(NO3)2, urea-N [CO(NH2)2], ammonium-N as (NH4)2SO4, nitrate-N+urea-N, nitrate-N+ammonium-N and a control (no N fertilizer)} were factorially combined with three levels of salinity to give a total of 18 treatments that were replicated three times. Each of the five levels of applied N was at the rate of 100 kg ha−1. The salinity levels (ECe) were 6.2 and 12.1 dSm−1, denoted as S 1 and S 2 and untreated soil (S 0), respectively. A basal dose of phosphorus (P) and potassium (K) was also applied. Five wheat plants were grown in each pot for six weeks. Data were collected for shoot and root biomass and shoot samples were analyzed for N, P, K, calcium (Ca), magnesium (Mg), sodium (Na), chloride (Cl), and micronutrients contents. Plant growth and nutrient uptake were influenced by both salinity and source of N. As expected, increasing salinity decreased dry matter production of shoot and root, whereas N application increased plant growth across all levels of salinity. The total dry biomass (shoot and root) of wheat was significantly higher in combined N treatments than in single sources. Irrespective of N forms most of the nutrient concentrations in the shoot was increased with increasing level of salinity. Among the fertilizers the concentration of cation was higher in nitrate-treated plants than in other forms of N. Ammonium-N and urea-N tended to inhibit the uptake of cations compared to nitrate-N under saline conditions. The trend for P and Cl concentration was almost opposite to that of cations concentration in the shoot. The uptake of nutrients seemed to be influenced by cation–anion balance in soil-plant system. Nitrogen concentration of shoot was greatly enhanced by all forms of N in the following order: Ni>NiAm>Am>NiUr>Ur>control. The interactive effect of salinity and fertilizer on iron (Fe), manganese (Mn), and zinc (Zn) contents was not consistent. Among the fertilizers the concentration of trace elements in the shoot was also not significantly different. It was concluded that the plant growth and nutrient concentration of shoot could depend upon N source and level of salinity. The mixed application of both ammoniacal and nitrate forms of N could possibly be conducive to plant growth in salt affected soils.

Effect of drought on ear and flag leaf photosynthesis of two wheat cultivars differing in drought resistance

We investigated net photosynthetic rate (PN) of ear and two uppermost (flag and penultimate) leaves of wheat cultivars Hongmangmai (drought resistant) and Haruhikari (drought sensitive) during post-anthesis under irrigated and non-irrigated field conditions. The PNof ear and flag leaf were significantly higher and less affected by drought in Hongmangmai than in Haruhikari. The rate of reduction in stomatal conductance (gs) was similar for the two cultivars, but intercellular CO2concentration (Ci) in the flag leaf of Hongmangmai was lower than that of Haruhikari in non-irrigated treatment. No differences were observed in leaf water potential (ψ1) and osmotic adjustment of the flag leaf of the cultivars. These results imply that differences in photosynthetic inhibition on the flag leaf at low leaf ψ1between the cultivars were primarily due to non-stomatal effects. Hence the main physiological factor associated with yield stability of Hongmangmai under drought stress may be attributed to the capacity for chloroplast activity in the flag leaf, which apparently allows sustained PNof flag leaf during grain filling under drought stress. The higher PNof ear in Hongmangmai under drought could also be related to its drought resistance.

Nitrogen Mineralization Under Saline Conditions

Abstract The conversion of soil nitrogen (N) from its organic into inorganic forms has been the subject of several investigations, but information on N mineralization in saline soil is scanty. The study was therefore carried out to observe trends in N mineralization in saline soils amended with manure and urea. The electrical conductivity (ECe) of saline soils was 0.2 (S0), 4.1 (S1), and 11.4 dSm−1 (S2). The N sources were applied at the rate of 300 kg N ha−1 and incubated for 8 weeks at 25°C. The pattern of N mineralization was a function of both soil salinity and N sources. The amount of NH4‐N released was significantly higher in S0 than S1 or S2, especially in urea treated soils. The NH4‐N release varied in the order of urea>manure>control with a peak period of release at the 4th week of incubation. Nitrification of NH4‐N to NO3‐N was reduced by salinity treatments. Patterns of NO3‐N release during incubation were opposite that of NH4‐N. Total mineralized N was highest in the urea treatment. Manure application increased ECe of soil by 18%.

Nitrogen transformation in four Japanese soils following manure+urea amendment

Understanding the effects of manure amendment on soil nitrogen (N) mineralization is crucial for a better assessment of N supplying potential of manure to maximize crop yield and minimize possible contamination of surface and belowground water resources. The effects of manure amendment on N mineralization were therefore studied under laboratory conditions. Surface (0–30 cm) samples of four Japanese soils: Andosol, red-yellow soil, masatsuchi, and sandune soil were each treated with chicken manure (PM), cattle manure (CM), swine manure (SM), ostrich manure (OM), and urea, and incubated for 8 weeks at 25°C. Nitrogen mineralization was studied in a 2 M KCl extract of samples collected at weekly intervals. The results showed that N mineralization was affected by both soil and manure types. NH4-N was found to be the dominant form of mineral N while appreciable increases in NO3 levels were observed during the 7th week. The rate of net N mineralization was highest in urea-treated soils, and the stimulating effect of urea on soil N mineralization was noted in the soils. Nitrogen mineralization from manure-treated soils was very low, suggesting that their N effect in the short-run should not be overvalued. In Andosol, CM and OM treatments exhibited negative N fertilizer effects. Ostrich and chicken manures showed high potentials for raising the pH of masatsuchi and sandune soils.

Effect of Foliar Application of Urea on Reproductive Abscission and Grain Yield of Soybean

Abstract Soybean (Glycine max L., Merr.) is considered to have relatively high level of reproductive abscission, but research information on how fertilizer use influences this problem is scanty. Field trials were therefore carried out for two seasons (1996 and 1998) to investigate the abscission levels of three soybean cultivars (TGX 536‐02D, TGM 579, and Samsoy 11) as affected by foliar application of urea during the early reproductive stages. Flowering was not significantly increased by urea application, although all fertilized plants had fewer flower abortions than control. Fertilizing twice at full‐flowering and pod‐setting (R2–R3) or thrice at first‐flowering, full‐flowering, and pod setting (R1–R2–R3) stages gave the least flower abortion. In TGX 536‐02D the average flower abortion was 61% in 1996 and 57% in 1998. The abortion rate was about 60% for TGM 579 in 1996 and Samsoy 11 in 1998, respectively. Percentage pod abortion was generally reduced especially at the R1–R2–R3 stage, while the proportion of aborted grains was highest in the unfertilized plants. Fertilizing at R2–R3 and R1–R2–R3 reduced seed abortion by about 8% in TGX 536‐02D. The grain yield of fertilized soybean was between 6 and 68% higher than the control. These increases were attributed to higher number of pods and meaningful reductions in flower and pod abortions. Foliar applied urea at R2–R3 gave satisfactory results but the best stage of application was R1–R2–R3.

Effect of sowing dates on the incidence of bacterial blight and yield of cotton

Abstract Bacterial blight (BL) is a common disease affecting the growth, development and yield of cotton in Sudan. Field trials were conducted for two seasons to determine the influence of four sowing dates (July 15 and 31, August 15 and September 1), representing heavy and low rainfall periods, on disease incidence and growth of two cotton cultivars (Barakat 90 and Barac (67)B. For the two cultivars, the incidence of BL decreased with delayed sowing. However, the number of cotton bolls was significantly decreased and seed cotton yield was reduced by an average of 12, 20 and 33% in the last three sowing dates compared with sowing in mid July. Fiber bundle strength and micronaire readings were also markedly reduced by delayed sowing while fiber length was unaffected. Bacterial blight reduced chlorophyll concentration (on dry leaf weight basis) by 80, 52, and 19% in severe, moderate and low disease infections, respectively. However, chlorophyll concentration of uninfected leaves was increased by delayed sowing. When sowing was delayed to mid August and early September, the total soluble carbohydrate of uninfected leaves of Barakat 90 was significantly reduced compared with mid and late July sowing. Our results indicate that sowing date is a more important factor that determines cotton yield and yield components than disease incidence and severity. Bakterielle Fleckenkrankheit (BL) ist eine weitverbreitete Krankheit, die Auswirkungen auf das Wachstum, die Entwicklung und den Ertrag von Baumwolle im Sudan hat. Uber zwei Wachstumsperioden wurden Feldversuche durchgefuhrt, um den Einfluss von vier Aussaatterminen (15. und 31. Juli, 15. August und 1. September) auf die Erkrankung und das Wachstum von zwei Baumwollsorten (Barakat 90 und Barac (67)B) zu bestimmen, die Perioden mit starken und geringen Niederschlagen reprasentieren. Bei beiden Sorten nahm das Auftreten von BL mit verzogertem Saattermin ab. Die Anzahl der Baumwollsamenkapseln war jedoch signifikant verringert und im Vergleich zur Aussaat Mitte Juli war die Baumwollsaat-Ernte durchschnittlich um 12, 20 und 33% bei den letzten drei Aussaatterminen verringert. Die Faserbundelstarke und Micronaire-Werte wurden ebenso deutlich durch die verzogerte Aussaat verringert, wahrend die Faserlange nicht beeinflusst wurde. Bakterielle Fleckenkrankheit reduzierte die Chlorophyllkonzentration (auf Blatt-Trockengewicht-Basis) um 80, 52 und 19% bei schweren, gemasigten und geringen Krankheitsinfektionen. Die Chlorophyllkonzentration nicht infizierter Blatter war jedoch durch die verzogerte Aussaat erhoht. Wurde die Aussaat bis Mitte August und Anfang September verzogert, waren die gesamtloslichen Zucker bei nicht infizierten Blattern der Sorte Barakat 90 im Vergleich zu den Aussaaten Mitte bis Ende Juli signifikant reduziert. Unsere Ergebnisse lassen vermuten, dass der Aussaattermin ein wichtigerer Faktor fur die Bestimmung der Baumwollernte und die Erntezusammensetzung ist als das Auftreten und die Schwere der Krankheit.

Ameliorative Effect of K-type and Ca-Type Artificial Zeolites on the Growth of Beets in Saline and Sodic Soils

Abstract Beets were grown on soils with various exchangeable sodium percentages (ESP). A saline non-sodic soil (SA, ESP = 3.2), a saline sodic soil (SO, ESP = 23), and a saline high sodic soil (HSO, ESP = 78) were prepared from Tottori sand dune soil (CO). K-type and Ca-type artificial zeolites (50 g kg−1) were applied to these soils in order to evaluate their effects on the chemical properties of saturation extracts of the soils, water deficit, cation uptake and transport, and cation balance of beet plants. In the zeolite-free treatments, beet growth was accelerated in SA and SO, but was suppressed in HSO compared with CO. The addition of both types of zeolites ameliorated plant growth in all the soils studied, especially HSO. The relative dry weight of the soils treated by the K-type zeolite to the zeolitefree soil was 189% for CO, 125% for SA, 130% for SO, and 222% for HSO. For the soils treated with the Ca-type zeolite, the values were 169, 116, 132, and 341%, respectively. In SA, SO, and HSO, the addition of the K-type zeolite increased the K uptake due to the increase of the K concentration of saturation extracts of soils. The addition of the Ca-type zeolite increased the Ca uptake due to the increase in the Ca concentration of the saturation extracts of soils which was accompanied by an increase in the K uptake. The increase in the uptake of K or Ca and decreased in the transport of Na by the addition of both types of zeolites improved the cation balance of the plants. The Ca-type zeolite did not increase the water deficit even though it increased the electric conductivity in all the soils. The results indicated that both types of artificial zeolites were able to improve the growth performance of beets in saline and sodic soils and that the K-type zeolite could be used as a K-fertilizer as well.

Soil physical and micronutrient changes following clearing of a tropical rainforest

One of the options for achieving an adequate food supply in tropical Africa is by bringing more land into production. This often requires clearing and developing new vegetation areas for agricultural production. In sub-Saharan Africa, large areas of forest are being cleared for cultivation without adequate knowledge as to the consequences of the clearing method employed. This study was therefore initiated to, among other objectives, assess the effects of some forest clearing methods on soil compaction, texture, and micronutrients. Treatments were the following five clearing methods: (1) mechanical (MC), (2) semi-mechanical (SMC), (3) slash and burn (manual) (SB), (4) mechanical – no planting (MCNP), and (5) slash and burn – no planting (SBNP). After clearing, we planted maize and cowpea in every other row during the first year, and planted maize and cassava during the second year in the plots of treatments 1–3. Changes in soil texture, bulk density, and exchangeable Fe, Zn, Mn, and Cu were determined. Soil bulk density increased (with depth) in all treatments from the intitial (0–15 cm) level of 1.1 g cm−3 to between 1.27 and 1.39 g cm−3 2 years after clearing, with the highest levels occurring in the MC plots. This indicated that clearing was accompanied by soil compaction. Some changes were noted in soil textural composition, but these were not of practical significance. Exchangeable Mn, Fe, and Cu (0–15 cm) decreased markedly after clearing, especially under MC in the first year. Zinc levels changed little during the study period. The decline in micronutrient levels was paralleled by a decline in soil organic carbon.

Influence of Forest Clearing Methods on Nutrient Uptake of Some Tropical Food Crops

The adverse effects of forest clearing on crop yield have often been directly ascribed to decline in soil fertility. However, the effect of various forest clearing methods on crop nutrient uptake as reflected by the content in the leaf tissues has been the subject of few scientific investigations. A study to determine the effect of forest clearing on nutrient content of some arable crops was, therefore, carried out in the tropical rainforest of south-western Nigeria. Three forest clearing methods—mechanical, semi-mechanical and manual clearing—were used, while maize, cowpea, and cassava were the test crops. Nutrient content in the tissues of these crops was assessed by sampling maize ear leaves at silking, youngest mature leaves (YML) of cowpea at flowering and YML of 3-month-old cassava for analysis. Correlation analysis was carried out to establish the relationship between nutrient content and crop yield. The method of forest clearing had no significant effect on the nutrient content of maize and cowpea during the first cropping cycle. However, nutrient content of maize in the manually cleared plots was higher than those in the semi- and mechanically cleared plots for all elements analyzed except Mg. Nitrogen content of cowpea was much higher than that of maize. Except for P and K, the nutrient content of cassava was not markedly different among the forest clearing methods. Calcium and P content in the leaves of maize and cassava varied inversely with their levels in the soil, implying that crop uptake could have accounted for the differences in their availability within the soil. Nitrogen, P and K had significant positive correlations with maize yield (r = 0.77, 0.89, and 0.71). Potassium content also had significant positive correlation with cassava root yield (r = 0.69). This is not surprising because compared with other crops, cassava requires large amounts of K for starch formation and root development. It is concluded that differences observed in crop yields under different forest clearing methods are a function of nutrient uptake and availability within the soil. However, the uptake of some nutrients does not seem to be determined by the level of soil availability alone.