Tsuneyoshi Endo

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.

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.

An evaluation of aerobic and anaerobic composting of banana peels treated with different inoculums for soil nutrient replenishment.

This study sought to evaluate the efficacy of aerobic and anaerobic composting of inoculated banana peels, and assess the agronomic value of banana peel-based compost. Changes in the chemical composition under aerobic and anaerobic conditions were examined for four formulations of banana peel-based wastes over a period of 12 weeks. The formulations i.e. plain banana peel (B), and a mixture with either cow dung (BC), poultry litter (BP) or earthworm (BE) were separately composted under aerobic and anaerobic conditions under laboratory conditions. Inoculation with either cow dung or poultry litter significantly facilitated mineralization in the order: BP>BC>B. The rate of decomposition was significantly faster under aerobic than in anaerobic composting conditions. The final composts contained high K (>100 g kg(-1)) and TN (>2%), indicating high potential as a source of K and N fertilizer.

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.

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.

Soils on the Loess Plateau

Morphological characteristics of soils on the Loess Plateau are products of its distinctive physical properties and behavior of water and salt in soil profiles. Various types of soils are distributed across the plateau, where rapid environmental changes occur because of long-term artificial contributors to loessial sediments. Soil health in this region has declined, owing to the fragile environment. In a case study of the Luohui Irrigation Scheme, soil morphological characteristics and soil salinization were related to the topographic sequence of the soils. Soil salinization differed within this scheme and subsoil texture was a useful indicator of the state of salt accumulation. This information may help develop guidelines for agricultural soil management that are based on underground water dynamics and soil morphological properties. A proper conservation strategy is necessary to achieve an optimal combination of land use for soils on the Loess Plateau.

Potassium, Calcium, and Magnesium Mineralization in Manure-Treated Soils

Studies into cation release in manured soils are very limited and poorly documented. The present investigation was therefore aimed at comparing the influence of manure application on cation [calcium (Ca), magnesium (Mg) and potassium (K)] mineralization in four different soils. Four sources of livestock manure: chicken manure (PM), cattle manure (CM), swine manure (SM), ostrich manure (OM) and a control (no manure) were added to the soils (Andosol, red–yellow soil, masa soil, and sandune soil) and incubated for 8 weeks at room temperature. Soils were sampled at weekly intervals and analyzed for pH, EC, and exchangeable Ca, Mg, and K. Soil pH increases ranging between 5.8 in CM and 6.6 in OM treatments were observed. Chicken manure increased EC from the mean initial level of 4.4 to 11.8 mS/m. Cumulative mineralized Ca and Mg was highest in red–yellow soil followed by masa soil. The lowest values for Ca (1.8 cmolc kg−1) and Mg (1.3 cmolc kg−1) were in Andosol.

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.

Agronomic and Environmental Performance of Rapeseed Oilcake in the Lowland Rice Farming of Japan

The use of organic manures as an alternative to chemical fertilizers is an option for the development of sustainable farming systems in Japan. The present study examined the effect of rapeseed oilcake (RO) not only on yield and yield components of rice (Oryza sativa L.) but also on soil fertility parameters and surface water quality in a paddy field by comparing them with the effects of conventional inorganic fertilizer (IF) and a control (CR), that is, natural (unfertilized) system. The long-term field experiment from 1990 to 2006 demonstrated the indigenous sustainability of paddy systems, because husked grain yield and shoot biomass in the CR plot remained at moderate levels (ave. 323 ± 56 g m−2 and 843 ± 166 g m−2, respectively) over 17 successive years. Meanwhile, the application of RO comparatively improved grain yield (ave. 538 ± 83 g m−2) and shoot biomass (ave. 1478 ± 187 g m−2) to almost the same level as with IF (ave. 538 ± 68 g m−2 and 1511 ± 173 g m−2, respectively) during the study period. Soil fertility assessment in the last experimental year (2006) indicated that RO could improve the soil quality to the same extent as IF because major fertility parameters showed similar values between the RO and IF plots. On the other hand, the application of IF induced a substantial increase in estimated load outflows of nitrogen (N) and phosphorus (P) from the paddy surface water (2.46 g N m−2; 0.38 g P m−2) as compared to the CR plot (0.92 g N m−2; 0.06 g P m−2). Outflows from the RO plot showed relatively lesser effluent loads (2.00 g N m−2; 0.14 g P m−2) than the IF plot. From the findings of this study, we concluded that RO is agronomically similar to but an environmentally better resource material than conventional IF in the lowland rice farming system in Japan.

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.