Toshimasa Honna

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.

RICE GROWTH AND NUTRIENT UPTAKE AS AFFECTED BY LIVESTOCK MANURE IN FOUR JAPANESE SOILS

One of the measures being adopted for relieving environmental problems arising from agricultural production is to recycle animal manure and other organic products as fertilizers and soil amendment. In Japan, this is a usual practice among farmers. In this study, we evaluated the effects of chicken manure (PM), cattle manure (CM), swine manure (SM) and mixed manure (MM = PM + CM + SM) on the growth, dry matter yield, and nutrient [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] uptake of rice (Oryza sativa Var. koshihikari). Four naturally infertile soils, andosol (A), red-yellow soil (RY), sandune soil (SD), and masatsuchi (M), were amended with 100 Mg ha−1 (dry weight) of each of the manure and allowed to stabilize for 4 weeks before rice was seeded. Changes in rice growth as indicated by plant height and number of leaves and tillers were monitored for 6 weeks, and the biomass yield was determined. Shoot samples were also analyzed for nutrient uptake. The amended A and RY soils produced the best effects on all the rice parameters studied. However, the number of rice leaves were significantly higher in RY than A. The manure effects on rice growth and biomass yield were ranked as CM > MM > SM > PM. Amending the soils with manure significantly delayed seedling emergence. Andosol amended with CM and MM produced significantly greater roots than with other manures. Masatsuchi amended with PM had lower shoot and root biomass than even the control. Among the manures, the uptake of all nutrients was highest in CM. The higher dry matter yield of rice in soils amended with CM and MM may be due to better nutrient balance and relatively lower levels of toxic factors in the material.

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.

SODIUM-CALCIUM EXCHANGE SELECTIVITY AS INFLUENCED BY CLAY MINERALS AND COMPOSITION

Knowledge of exchangeable cation chemistry can provide clues about tendencies toward either soil dispersion or flocculation as exchangeable sodium accumulates. The accumulation of sodium might be influenced by soil texture and degree of salinity. The effects of clay minerals, composition, and salinity of solution on Na-Ca exchange selectivities of montmorillonite and illite were studied. Regression equations for the exchangeable sodium ratio (ESR)-sodium adsorption ratio (SAR) differed according to clay minerals, composition, and salinity of equilibrated solutions. The experimental Na-Ca exchange selectivities in this study differed from the values reported by U.S. Salinity Laboratory Staff. Our values were influenced by clay minerals, composition, and salinity of equilibrated solutions. Compared with montmorillonite, the affinity of illite for Na was high and decreased with increasing clay content. This phenomenon was obvious at the low SAR and high salinity of equilibrated solutions, based on colloidal properties. These findings suggest that the affinity of the soil for Na increases with soil salinization. In soil with low clay contents, Na adsorption/Ca release in the soil colloids was enhanced, as was soil sodicity. Therefore, the exchangeable sodium percentage of the soil increased rapidly, leading to the formation of sodic soils. Conversely, Na adsorption/Ca release in the soil colloids was comparatively suppressed in soil with high clay contents. The affinity of the soil for Na increased with increasing salinity of soil solution through the accumulation of salt in the soil. It can therefore be concluded that sodic soils are formed during the process of soil salinization in soil with high clay contents.

Changes in Humic Substances and Phosphorus Fractions During Composting

The behavior of humic substances (HS) and phosphorus (P) fractions in livestock manure co-composted with rice straw was studied by chemical and spectroscopic analyses. Composting was accompanied by a decrease in the levels of carbon (C) and nitrogen (N) as well as HS and fulvic acid (FA) fractions. The elemental content (weight %) of humic acid (HA) extracted from the compost showed a high C content and low oxygen (O) content, possibly due to a low degree of oxidation. The N/C and H/C ratios of HA decreased as the compost matured, whereas the O/H and O/C increased. The decline in the H/C ratio from 1.24 at 0d to 1.0 at 195d indicated an increase in the aromatic structure of the HA. The absorbance curve for the HS showed a decrease in the slope with time, up to 42d. The optical density of HS increased with time of composting with a peak at 42d. Also the Δ log K values of FA increased appreciably with time of composting whereas those of HS and HA were little changed. Water-soluble and HCl-soluble-P were the dominant fractions of P in the compost, and ranged between 18 and 39% and 18 and 36%, respectively. However, the former declined progressively with time of composting, while the latter increased, indicating transformation of the more vulnerable water soluble P to the more recalcitrant HCl-extractable P.

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%.

Comprehensive assessment of the clay mineralogical composition of lowland soils in West Africa

Abstract The clay mineralogical composition of 87 topsoil (0–15 cm) samples from inland valleys (IVs) and flood plains (FPs) in seven West African countries, namely Côte d’Ivoire, Ghana, Guinea, Mali, Niger, Nigeria and Sierra Leone, was examined using X-ray diffraction analysis to gain basic information for the development of sustainable lowland agriculture in the region. The results of the present study revealed that the clay fraction (< 2 m) of these samples consisted of 68.4% of 7 Å minerals (low-activity clays such as kaolin minerals), 26.6% of 14 Å minerals (relatively high-activity clays such as smectite and vermiculite) and 5.1% of 10 Å minerals (illite or clay micas) and showed a high variability in the composition. With respect to the soil material classification based on the relative abundance of these three types of minerals, Type 7 (rich in 7 Å minerals) accounted for 42.5% of the total samples, while 39.7% of all the samples were Type 7-10 and 7-14 with a predominance of 7 Å minerals and with negligible amounts of 10 and/or 14 Å minerals, respectively. Type 14-7 accounted for 17.2% of the total samples and was only recorded in Nigeria. The other clay mineral types (i.e. Types 7-10-14, 14, 10, 10-7, 10-14 and 14-10) that were composed mainly of 10 and/or 14 Å minerals were hardly found in the West African lowland soils, whereas Types 14 and 7-10-14 were observed in a vertic soil of Southeast Ghana and in northern Ghana, respectively. In contrast, no significant differences in the clay mineralogical composition were found between the IV and FP soils. Geographical distribution of the soil types showed that the soils in the eastern part of West Africa contained more 14 Å and 10 Å minerals than those in the western part. Although the effect of agro-climatological differences was not conspicuous, soils in the Sahel and Sudan savanna zones showed a higher percentage of 14 Å clay minerals than those in the Guinea savanna and equatorial forest zones. The findings were as follows: (1) the low fertility status of the lowland soils in the region was closely associated with their poor mineralogical characteristics (i.e. predominance of 1:1 type clay minerals and a lower amount of 2:1 type clay minerals), (2) no significant differences in the mean clay mineralogical composition were observed between the IV and FP soils, indicating that the lower fertility of the IV soils mainly resulted from the lower clay content, (3) the clay mineralogy of the West African lowland soils was more strongly influenced by the nature of the parent materials than by the climatic conditions and relief.

The Relationship Between Total and Available Heavy Metals in Composted Manure

ABSTRACT Composting of livestock manure is a viable and environmentally sound method of waste management. It is usually an aerobic process, but anaerobic composting through use of digesters is also a widely practiced waste management option, due to its cost efficiency. Although physicochemical changes during composting have been documented, information on the behavior of total and available heavy metals during composting of livestock manure is scanty. Such information is necessary for an efficient compost use and environmental management practice. In the present investigation, we compared the behavior of total and available heavy metals in a mixed cattle + swine + chicken manure which was composted for 195 days, with and without air, using rice straw as a bulking agent. Marked increases in total Fe, Zn, Cu and Mn, especially under anaerobic conditions were noted during composting. Conversely, aerobic composting significantly decreased available Fe by 36%, Zn by 50%. Cuby 14% and Mn by 27% at 195 days. The decreases could be due to complexation with other ions and/or organic matter. The available Fe increased by 59% and Zn by 87%, while available Cu decreased by 16% and Mn by 22% under anaerobic conditions. Whereas 76% and 56% of the variations in available Fe and Zn were due to the changes in their total contents under anaerobic conditions, only 14% and 2% of such variations were so attributed under aerobic conditions. For available Cu and Mn, 65% and 39% of the variations in their levels under aerobic composting could be explained by the changes in total Cu and Mn compared with only 3% and 14% under anaerobic conditions. On the basis of these results, manures from sources such as anaerobic digesters may have a higher potential for metal, especially. Fe and Zn export to the environment upon application to soils. Factors other than total content may be responsible for the availability of Fe and Zn in aerobic compost. Since aerobically composted manure had low metal levels in available forms, it could ensure a slow release upon application to soils, which could be managed to synchronise with plant requirement.

PHYSICO-CHEMICAL CHANGES IN LIVESTOCK FECES DURING COMPOSTING

The properties of livestock manure during composting were studied in order to understand the changes in physical and chemical composition. The composting was carried out in a commercial organic fertilizer plant utilizing aerobic processes, and the following parameters were measured in samples collected at different stages of composting: moisture content, temperature, total carbon (C), humic substance (HS) contents and fractions-fulvic acid (FA) and humic acid (HA), and macro- and micronutrients. Correlation analysis was carried out between these manure properties. Total C and nitrogen (N) decreased by 18 and 10% in the final manure at the end of composting. During composting, HA became progressively the dominant fraction of HS. Phosphorus (P) increased by 31%, potassium (K) by 12%, magnesium (Mg) by 11%, and calcium (Ca) by 6%, respectively. The C/N ratio decreased slightly from an initial value of 14.8 to 12.9 after the composting process. The compost was highest in iron (Fe) and lowest in copper (Cu) content. Highly significant positive correlations were found between total N and HS, implying that HS could be the major determinant of N level in the manure. Significant positive correlations were obtained between zinc (Zn) and HS and FA whereas a highly significant positive correlation was noted for manganese (Mn) and HA. Since the content of N tended to decline during composting, it could be necessary to supplement the manure with inorganic sources of N depending on soil nutrient status and crop requirement.

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.