Haplic Lixisol Research Articles

Soil properties and agronomic effects of repeated biochar amendment and fertilization in an urban horticultural system of Burkina Faso

Biochar application can improve soil quality and plant growth, particularly in combination with organic and mineral fertilization. However, data on its effectiveness in intensively managed (fertilized) gardens within the urban and peri-urban (UPA) agriculture of West Africa is sketchy. We, therefore, studied the medium-term effects of repeated biochar produced from agricultural residues, composted faecal amendments (ECOSAN), and inorganic fertilization on small-scale, intensive urban vegetable production in multiple crop rotations over four years. The experiment used a randomized factorial design comprising different soil management and irrigation practices on a Haplic Lixisol in Ouagadougou, Burkina Faso during eight cropping cycles. Biochar amendment resulted in increased soil organic carbon (SOC) on plots under farmers’ practice (cattle manure + urea). Repeated biochar application at 20 t ha−1 increased SOC by 51 %. Mineral fertilization alone decreased SOC by 32 % (from 12.7 to 8.6 g C kg−1 soil) after 6 months with a progressive decline and soil acidification over time. During this period fertilization with ECOSAN at 16–23 t ha−1 per cropping cycle increased yields and soil pH from 6.5 to 7.4. Four years after its application biochar still increased total fresh matter yield of cabbage by 32 % but showed no effect on amaranth while repeated biochar application only increased total fresh matter yields of the first crop after reapplication. Nitrogen use efficiency (NUE) was higher with mineral fertilizer (NPK) and mineral fertilizer in combination with organic fertilizer (FP) than with ECOSAN alone. The study demonstrates effect of biochar on SOC with less pronounced, crop-specific agronomic benefits.

Under a Tropical Climate and in Sandy Soils, Bat Guano Mineralises Very Quickly, Behaving More like a Mineral Fertiliser than a Conventional Farmyard Manure

In sub-Saharan Africa, soil fertility management must rely on local fertiliser resources since most smallholder farmers do not have access to industrial fertilisers. In Vilankulo, Mozambique, farmers have access to bat guano and biochar, albeit in small amounts, which makes it even more necessary to manage them correctly to maximise crop productivity. This study was carried out with irrigated maize (Zea mays L.) in a haplic Lixisol during the 2017/2018 and 2019 growing seasons. Nine treatments were established consisting of the application of 5 (G5) and 10 (G10) t ha−1 of guano at sowing, 5 (B5) and 10 (B10) t ha−1 of biochar at sowing, 5 [G5(-1)] and 10 [G10(-1)] t ha−1 of guano one month before sowing, 1 and 4 (B1G4) and 2 and 8 (B2G8) t ha−1 of biochar and guano, respectively, at sowing and an unfertilised control (C). Treatments G10 and B2G8 led to the highest maize yields (3.77 and 2.68 t ha−1 in 2018 and 5.05 and 5.17 t ha−1 in 2019, respectively), and were statistically higher than those of the control (1.35 and 1.63 kg ha−1, respectively). Apparent nitrogen recovery from bat guano was close to 100%, showing almost complete mineralisation during the maize growing season, due to its low carbon/nitrogen ratio and very favourable environmental conditions for mineralisation. Due to the fast release of nutrients, bringing forward the application of the organic amendment before sowing is not recommended, since it reduces nutrient use efficiency. Biochar did not significantly influence maize grain yield or contribute significantly to plant nutrition. To take advantage of its potential effect on some soil properties, its use in combination with other materials of greater fertilising value is recommended.

Carbon and nitrogen stocks and microbiological attributes of soil under eucalyptus cultivation in the Pampa biome of southern Brazil

In the south of Brazil, the intensification of eucalyptus planting can impact the local biome, characterized by grasslands that extends to Uruguay and Argentina. Thus, the objective of the study was to evaluate changes in soil carbon, nitrogen and their labile fractions and soil microbiological attributes due to the introduction of eucalyptus cultivation in the Pampa biome. The soils evaluated were Eutric Regosol (RG), Haplic Lixisol (LX), Dystric Leptosol (LP) and Pellic Vertisol (VR). For this, areas of homogeneous cultivation of Eucalyptus saligna (7 years old) and areas of grassland (native vegetation) were selected. Physical granulometric fractionation of soil organic matter (SOM) was performed in the 0–5, 5–10 and 10–15 cm soil layers, quantifying levels, stocks and distribution of total organic carbon (TOC) and total nitrogen (TN) in the labile and associated with minerals fractions, and the carbon management index (CMI) was calculated. In the 0–5 and 5–10 cm soil layers, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), basal soil respiration, metabolic coefficient, MBC / TOC, MBN / TN, MBC / MBN ratios were also evaluated. Eucalyptus cultivation increased the TOC and POC carbon stocks by 8.7 and 21.7%, respectively (0-15 cm) in compared to grassland. It was also observed that the cultivation of eucalyptus increased 6.7% and 26.0% the stocks of TN and PN, respectively, compared to grassland in the pampa biome. Carbon stocks associated with minerals were not affected by eucalyptus cultivation. The cultivation of eucalyptus increased the basal respiration and the microbial biomass carbon in relation to grassland and there is a reduction of microbial biomass nitrogen in the soil. Thus, the cultivation of eucalyptus in the Pampa biome in southern Brazil demonstrates that it is a forest crop that can contribute to the increase in total and labile carbon stocks and also the biomass and microbial activity of the soil, which are important indicators of assessment of soil quality.

Agronomic performance of urea in pastilled compositions applied on maize fertilization

Urea pastillation is a technology that allows the composite mixture with other elements like sulfur and zinc. This study aimed to provide recommendations of N rates, and to assess the agronomic performance of N fertilizers, including pastille urea and its composition associated with S and Zn, top-dressed on maize. Two experiments were set up in the harvests of 2014 and 2015 in an Acrisol and a Lixisol. The experimental design was the randomized blocks with three replicates in a split-plot arrangement and an additional treatment (no N). In the plot, three N applications rates were tested (75, 150 and 300 kg ha-1); while in the subplots, seven fertilizers were tested, including conventional and pastilled ones. The greater was the N rate applied, the higher were the leaf N content and grain yield of maize. The S content in the leaves increased with the increasing S doses applied with the tested fertilizers. Yields with ammonium sulfate were higher than with prilled urea, pastille urea and pastille urea with elemental S in the harvest mean on the Haplic Lixisol. The rate that corresponded to the maximum economic efficiency for UR was 128 and 119 kg N ha-1 for Haplic Acrisol and Haplic Lixisol, respectively. The recommended dose of ammonium sulfate was 119 kg ha-1, since it provided the greater incomes for both sites.

Interactive effects of conservation tillage, residue management, and nitrogen fertilizer application on soil properties under maize-cotton rotation system on highly weathered soils of West Africa

Loss of topsoil, enriched with nutrients, reduces soil fertility, and is one of the major impediments to sustainable crop production in West Africa. Appropriate management practices can lead to a stable restoration of land’s capacity to provide adequate ecosystem services. Thus, our study aimed to investigate the impact of alternative management practices and their interactions on topsoil (0–20 cm) organic carbon (SOCd), nutrient stocks [total nitrogen (STNd), phosphorus (SPd) and potassium (SKd)] under a maize-cotton rotation system on highly weathered soils of West Africa. To this end, on-farm trials were set up on four sites in the sub-humid Savanna of West Africa (2 in Benin (St1 and St2), and 2 in Burkina-Faso (St3 and St4)) in a strip-split plot layout, where 2 levels of tillage (contour ridge tillage, Ct and reduced tillage, Rt) were considered as main plot factor, and sub-plot factors included 2 levels of crop residue management (removed, CRr and incorporated, CRi), and 2 levels of N fertilizer (control, N0 and recommended rate, Nr). In 2016, after 5 cycles of annual maize-cotton rotation (2012–2016), the largest pool of soil nutrients was recorded on St3 (Haplic Lixisol, footslope in Benin), while the lowest content was observed on St1 (Ferric Lixisol, footslope in Burkina). When comparing the treatments, we found that Ct combined with CRi improved soil nutrient stocks in upslope sites, St2 (Eutric Plinthosol, upslope in Burkina) and St4 (Plinthic Lixisol, upslope in Benin), which are more prone to erosion. At the same time, footslope sites (St1 and St3) benefited from Rt coupled with CRi. CRi promoted an increase in SPd and SKd on all sites except St1 (Haplic Lixisol on footslope). The application of recommended dose of N fertilizer improved STNd under the Ct system in upslope regions and under the Rt system in footslope regions. However, no significant difference was observed for soil pH among the treatments across all sites. In summary, the efficiency of practices for conservation of soil nutrient stocks was closely related to landscape position of the field, which was correlated with soil moisture, textural class, and gravel content. Consequently, site-adapted tillage practices combined with residue incorporation are crucial for sustainable soil fertility management and crop productivity under maize-cotton rotation in smallholder production systems in West Africa.

Soil tillage, residue management and site interactions affecting nitrogen use efficiency in maize and cotton in the Sudan Savanna of Africa

Nitrogen (N) fertilizers applied to agricultural lands are often lost due to improper management practices. It is important to manage applied N fertilizers efficiently in order to promote sustainable crop production. In a two year (2013–2014) on-farm trial in the Sudan savanna of Benin (Dassari village) and Burkina-Faso (Dano village), we assessed the single and interactive effects of tillage and crop residue management on nitrogen uptake (NU) and nitrogen use efficiency (NUE) of cotton and maize in four different sites [S1 (Ferric Lixisol, footslope in Dano), S2 (Eutric Plinthosol, upslope in Dano), S3 (Haplic Lixisol, footslope in Dassari), and S4 (Plinthic Lixisol, upslope in Dassari)]. Two tillage practices, i) contour ridge tillage, and ii) reduced tillage, were considered as main plot factors, while the sub-plots consisted of two levels of crop residue management, i) with residue, and ii) without residue, and two levels of N fertilizer, i) control, and ii) recommended level of N fertilizer (45 kg ha−1 for cotton and 60 kg ha−1 for maize). We selected three indices, nitrogen fertilizer recovery efficiency (NFR), agronomic efficiency (AE), and partial factor productivity (PFPn) to describe the NUE of crops.Compared to reduced tillage, contour ridge tillage significantly improved NU and NUE indices of both cotton and maize on all sites except S3. When averaged across sites, implementation of contour ridge tillage instead of reduced tillage resulted in increase in NFR, AE and PFPn of cotton by 32.6%, 18.6%, and 20%, respectively. Also, NFR, AE, and PFPn of maize were increased by 29.4%, 25.8%, 1.7%, respectively under contour ridge tillage.Additionally, retention of crop residue significantly affected mainly NFR of cotton and maize, when averaged across sites. It increased NFR of cotton and maize by 14.6% and 14%, respectively, and enhanced NFR of cotton, yet not significantly on all sites.We concluded that increased soil N availability due to restricted horizontal soil water movement and improved soil water content is the primary contributor to increased NUE of both cotton and maize under the contour ridge tillage and crop residue retention across sites. However, such an effect was not notable on S3 as this site possesses improved soil hydrological properties a priori.

Soil physicochemical and hydraulic properties of petroleum-derived and vegetable oil-contaminated Haplic Lixisol and Rhodic Nitisol in southwest Nigeria.

Various daily human activities can result in the release of pollutants of different chemical constituents and specific gravities into natural soils. Pollution of natural soils is a recurring occurrence in the environment and it contributes greatly to the alteration of soils properties. The results of an assessment of the effects of selected petroleum-derived and vegetable oils on soil physicochemical and hydraulic properties are presented in this work. Topsoil samples at a depth of 0-20 cm of the same textural class were collected from the order Lixisols and Nitisol within Ogun State, southwest Nigeria. Surface soil samples were collected and treated with petrol, diesel and palm oil at two different volumes (50 and 100 ml). Investigated soil properties include particle size distribution, soil pH, bulk density (BD), total porosity (TP), saturated hydraulic conductivity (Ksat), available water capacity (AWC), total carbon (TC), total nitrogen (TN), organic matter (OM) content, cation exchange capacity (CEC), potassium, sodium, and soil resistivity. Analysis of variance and Pearson's correlation were used to study the variations of the relationship of analyzed soil properties under different soil types and treatments. The regression analysis shows that all the generated models for predicting Ksat values under different soil treatments had R2 values ranging from 0.999 to 1.000. Results showed that treatment with either petroleum-derived or lipids has no effects on soil pH and textural class. Results further revealed that palm oil contamination at 50 ml recorded least values of Ksat in the two soil types. In all cases, BD and Ksat of the contaminated soils of the two sampling locations were reduced compared with their control values. Correlation coefficient showed expected strong negative correlation between TP and BD as well as between any two of organic parameters (TC, TN, and OM) and soil resistivity, TC, and TN at 1% level in both soil types. Two-way ANOVA showed that there were significant differences at 5% level between the two locations with respects to BD, TP, and CEC while significant differences in Ksat, pH, TC, TN, and OM occur between soils from the two locations under various treatments at 5% level.

Biochar application and wastewater irrigation in urban vegetable production of Ouagadougou, Burkina Faso

In West Africa population growth and fast urbanization challenge food security for which urban and peri-urban agriculture plays an increasing role. Adding biochar to soils depleted in soil organic carbon may improve soil quality but its effectiveness in high input systems, such as urban horticulture in West Africa, is unknown. We studied the effects of fertilization, amended biochar from agricultural waste, irrigation water quality and quantity on small-scale urban vegetable production in a multi-factorial split-plot experiment on a Haplic Lixisol in Ouagadougou, Burkina Faso. A single application of corn cob biochar at the rate of 20 t ha−1 was used in a 2-year study covering eleven cropping cycles. Biochar significantly improved total fresh matter yields of two amaranth cycles by 39% and 17%, lettuce by 7% and carrot by 11%. Repeated measures analysis showed that biochar increased average total biomass by 9% and marketable yield by 6%. Biochar was effective on fertilized plots while plant growth on unfertilized plots was limited by nutrients, most likely nitrogen (N). A 33% reduction in irrigation water caused yield declines of 4–23% which was more pronounced in fertilized plots with higher water consumption by the larger plants. Biochar increased potassium (K) concentrations while wastewater reduced phosphorus (P) in plant tissue. The study showed a positive effect of biochar on crop yields and nutrition while wastewater effects were limited to nutrient deficient plots.

Assessment of the Physical and Chemical Properties of Three Contrasting Soils Under Different Land Use Systems

This study was undertaken to evaluate the physical and chemical properties of three contrasting soils under four land use systems. The soil types considered were Vertic Cambisol, Haplic Lixisol and Ferric Luvisol while the land use types studied are cocoa plantation (CP), grazing land (GL), fallow land (FL) and cultivated land (CL). Soil samples were collected at 0-15cm and 15-30cm depths respectively from each of the locations. The soil samples were air dried and passed through a 2mm sieve and taken to the laboratory for analysis. The result of the study showed a higher sand content being recorded in Haplic Lixisol (CL) and Ferric Luvisol 2 (FL) followed by that of Vertic Cambisol (CP) and Ferric Luvisol 1 (GL) in the upper 0 to15 cm depth and lower 15-30 cm. The soil pH within the soil types and depths could be categorized as slightly acidic to moderately alkaline. The organic carbon content of the soils was generally low; it varied from 0.18% to 1.29 % for 0 to 15 cm depth with Vertic Cambisol (CP) having the highest value. The mean available P content was not significantly (P≤0.05) different among the soil and land use types. The total nitrogen recorded was generally low 1.006 - 1.304% at 0-15cm while at the lower depth it ranged between 0.566 – 0.768%. The exchangeable bases also decreased following cultivation. The result of the study shows that continuous cultivation without adequate management practices causes a decline in the physical and chemical properties of the soil.

The effect of phosphorus and nitrogen fertilizers on grain yield, nutrient uptake and use efficiency of two maize (Zea mays L.) varieties under rain fed condition on Haplic Lixisol in the forest-savannah transition zone of Ghana

Low soil fertility is recognized as the major constraint to food production and food security in Ghana. An important practice that restores some level of fertility is long fallow, however this is no longer practiced due to increased pressure on land for other purposes. This has resulted in decline in crop yields in areas (forest-savannah transition zone or Sub-humid Ghana) which are known to be one of the major food baskets for the country. The soils are generally poor and require mineral fertilizer to increase crop productivity. In order to increase food production and crop productivity, the use of mineral fertilizer is required other than the expansion of arable land. The aim of this paper is to assess the influence of Phosphorus and Nitrogen fertilizers on the yield of two maize varieties and nutrient use efficiency in the forest-savannah transition zone of Ghana. Experimental data from two maize varieties (Zea mays L.) grown under four concentrations of nitrogen (N) and three concentrations of phosphorus (P) in the 2008 major and minor seasons at two sites in Ejura, Ghana, were used to assess the influence of P and N on the yield, nutrient uptake and use efficiency in the forest-savannah transition zone of Ghana. Analysis of variance showed a statistically significant effect of N and P on grain yield, total biomass, grain N uptake and apparent N recovery. Increasing N concentration significantly increased grain yield, grain N uptake and total dry matter production irrespective of application of P fertilizer. The application of P fertilizer increased N use efficiency with grain yield ranging from 918 (control) to 4953 kg ha−1 (N4P2) and 824 (control) to 4267 kg ha−1 (N4P2) for Obatanpa and Dorke maize, respectively. The two cultivars were significantly different from each other with higher grain yield produced by Obatanpa than Dorke. The application of inorganic P fertilizer increased the efficient utilization of inorganic N fertilizer by the plants in grain yield and total biomass production. Hence, P nutrition of soils is critical for the efficient use of inorganic N fertilizer in the area. Inorganic fertilizer use in the study area was agronomically efficient, though generally more efficient at the Ejura farm site (Experiment 1 and 3) than the Agricultural College site (Experiment 2 and 4). Owing to the spatial variability in soil nutrients in the study area, site-specific fertilizer testing is needed to increase nutrient use efficiency and crop productivity. To improve the rate of fertilizer adoption and use by farmers, the government should subsidize the cost of fertilizer to make it affordable for farmers to purchase to increase crop productivity.

PERMANENCE OF WATER EFFECTIVENESS IN THE ROOT ZONE OF THE CAATINGA BIOME

ABSTRACT Soil is an important water compartment into a watershed scale, mainly due to its role in providing water to plants and to the influence of antecedent moisture on the runoff initiation. The aim of this research is to assess the permanence of water effectiveness in the soil under preserved-vegetation constraints in the Caatinga biome, in the semiarid northeastern Brazil. For this purpose, hourly soil moisture measurements were collected with TDR and analyzed between 2003 and 2010 for three soil-vegetation associations in the Aiuaba Experimental Basin. The results showed that in nine months per year soil moisture was below wilting point for two associations, whose soils are Chromic Luvisol and Haplic Lixisol (Abruptic). In the third association, where the shallow soil Lithic Leptosol prevails, water was found non-effective four months per year. A possible reason for the high water permanence in the shallowest soil is the percolation process, generating sub-surface flow, which barely occurs in the deeper soils. In situ observations indicates that the long period of soil moisture below the wilting point was not enough to avoid the blooming season of the Caatinga vegetation during the rainy periods. Indeed, after the beginning of each rainy season, there is a growth of dense green vegetation, regardless of the long period under water shortage.

Nitrogen leaching and indirect nitrous oxide emissions from fertilized croplands in Zimbabwe

Agricultural efforts to end hunger in Africa are hampered by low fertilizer-use-efficiency exposing applied nutrients to losses. This constitutes economic losses and environmental concerns related to leaching and greenhouse gas emissions. The effects of NH4NO3 (0, 60 and 120 kg N ha−1) on N uptake, N-leaching and indirect N2O emissions were studied during three maize (Zea mays L.) cropping seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. Leaching was measured using lysimeters, while indirect N2O emissions were calculated from leached N using the emission factor methodology. Results showed accelerated N-leaching (3–26 kg ha−1 season−1) and N-uptake (10–92 kg ha−1) with N input. Leached N in groundwater had potential to produce emission increments of 0–94 g N2O-N ha−1 season−1 on clay soil, and 5–133 g N2O-N ha−1 season−1 on sandy loam soil following the application of NH4NO3. In view of this short-term response intensive cropping using relatively high N rate may be more appropriate for maize in areas whose soils and climatic conditions are similar to those investigated in this study, compared with using lower N rates or no N over relatively larger areas to attain a targeted food security level.

Effects of organic and mineral fertilizer nitrogen on greenhouse gas emissions and plant-captured carbon under maize cropping in Zimbabwe

Optimizing a three-way pact comprising crop yields, fertility inputs and greenhouse gases may minimize the contribution of croplands to global warming. Fluxes of N2O, CO2 and CH4 from soil were measured under maize (Zea mays L.) grown using 0, 60 and 120 kg N hm-2 as NH4NO3-N and composted manure-N in three seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. The fluxes were measured using the static chamber methodology involving gas chromatography for ample air analysis. Over an average of 122 days we estimated emissions of 0.1 to 0.5 kg N2O-N hm−2, 711 to 1574 kg CO2-C hm−2 and−2.6 to 5.8 kg CH4-C hm−2 from six treatments during season II with the highest fluxes. The posed hypothesis that composted manure-N may be better placed as a mitigation option against soil emissions of GHG than mineral fertilizer-N was largely supported by N2O fluxes during the wet period of the year, but with high level of uncertainty. Nitrogen addition might have stimulated both emissions and consumption of CH4 but the sink or source strength depended highly on soil water content. We concluded that the application of mineral-N and manure input may play an important role with reference to global warming provided the season can support substantial crop productivity that may reduce the amount of N2O loss per unit yield. Confidence in fluxes response to agricultural management is still low due to sporadic measurements and limited observations from the southern African region.

A comparison of surface applied granulated biosolids and poultry litter in terms of risk to runoff water quality on turf farms in Western Sydney, Australia

A simulated rainfall study was carried out on couch ( Cynodon dactylon cv) turf on a Haplic Lixisol soil at Camden in South Western Sydney, Australia, to compare surface applications of a new granulated biosolids product with poultry litter (the current turf farm practice) in terms of runoff water quality impacts. The granulated biosolids were surface applied to the turf at a total N loading of 240 kg N ha −1, equivalent to the current turf farm practice of applying 18.9 m 3 ha −1 of poultry litter. One week after the application of the organic fertiliser treatments, simulated rainfall was applied to each plot at an intensity of 90 mm h −1 for a period of 0.5 h, and all runoff water was collected and analysed for a range of important water quality parameters. The most significant result from this study was the finding that runoff water samples from the poultry litter treatment plots were found to contain 10 times more total P (12.3 mg l −1 compared to 1.2 mg l −1) and dissolved P (8.3 mg l −1 compared to 0.6 mg l −1) than that found in the runoff water samples from the biosolid treatment. The relationship between application total P loading (TPA) and runoff water total P concentration (RO-P) was significantly ( P < 0.05) different between the biosolids (RO-P:TPA ratio = 0.01) and poultry litter (RO-P:TPA ratio = 0.16) products, reflecting the importance of the chemical nature of the applied P in addition to the total loading. The phosphorus in the poultry litter was much more easily mobilised and transported in runoff than the biosolids P. For surface applications of these organic wastes, bicarbonate extractable P loading provided a better indication of runoff P contamination risk in the first flush of runoff, than total P loading. The runoff from the biosolid treatment plots also had lower levels of NH 4-N and salinity than the poultry litter plots, although both treatments had moderate levels of dissolved organic carbon in their runoff. Heavy metal levels in the runoff were below guideline limits for both organic amendments, while runoff pathogen levels were highly variable. Our findings highlight the potential benefits of using granulated biosolids as an alternative surface applied organic N fertiliser on turf farms for its lower risk to surface water quality as compared to poultry litter, the current practice.

Residual effect of leguminous crops and inorganic fertilizer on soil properties and maize grain yield

Soil management practices that utilize organic matter have great potential to increase productivity in sub-Saharan Africa. Field studies were carried out between September 1995 and August 1998 to determine the effects of three leguminous crop species: velvet bean ( Mucuna pruriens var. utilis ), groundnut ( Arachis hypogaea L.) and cowpea ( Vigna unguiculata (L.) Walp), and inorganic fertilizer on the soil properties and succeeding maize grain yield when grown in rotation on a sandy soil classified as Haplic Lixisol in the forest-savannah transition zone of Ghana. The legumes were established in the minor seasons and maize in all the plots in the major cropping seasons. A 2 × 3 factorial design laid out in a randomized complete block was used. The main plots consisted of three leguminous crop residues and the sub-plots of two fertilizer levels (0 and 45 kg N ha −1 , 19 kg P ha −1 , 19 kg K ha −1 ). The control consisted of maize following maize with the recommended fertilizer rate (90 kg N ha −1 , 37 kg P ha −1 , 37 kg K ha −1 ). On average the Mucuna plots added 4.0 t ha −1 of crop residue to the soil in a season and cowpea 1.0 t ha −1 . The preceding crops had little effect on the soil properties. Leaf area index, total dry matter and maize grain yields were significantly affected by fertilizer. The best maize grain yield (6787 kg ha −1 ) was recorded in the first year on Mucuna plots with half the recommended rate of fertilizer. The cropping sequence with Mucuna residue was the most efficient. The gap in maize grain yield between the fertilized and unfertilized treatments widened each successive year. The interaction between organic matter and fertilizer may have been limited due to the surface application of the organic residue.

Cattle manure effects on structural stability and water retention capacity of a granitic sandy soil in Zimbabwe

The evaluation of soil aggregate stability and water retention is important in the assessment of soil management options. A 3-year study was conducted in 1999 to determine the effects of two cattle manure application methods on soil aggregate stability and water retention capacity of a sandy soil (Haplic Lixisol). Manure application increased soil organic C by 10–38% in the 0–10 cm layer. Compared with the control, manure management treatments increased the aggregate stability of soil as measured by the mean weight diameter (MWD) and aggregates between 2 and 10 mm (AGG2) indices from 0.243 to 0.733–0.926 mm, and from 27.3 to 128.3–148.3 g kg −1, respectively. The readily available water (RAW) capacity of the soil was significantly increased by manure addition, whereas the increase in AWC was not significant. The increase in water retention capacity in the soil was more affected at low suctions and this was related to the effects of manure on macroporosity. It was concluded that cattle manure was beneficial to the structural stability and water retention of this soil.

Effect of termites and mulch on the physical rehabilitation of structurally crusted soils in the Sahel

The effectiveness of mulch and termite activity in the rehabilitation of the physical properties of crusted soil was studied in northern Burkina Faso (Province de Bam). A split plot design was used with three replications each being on one soil type. The soil types were Ferric Lixisol, Haplic Lixisol and Chromic Cambisol. The main factor was termite activity, and to this end dieldrin (0·50 kg a.i. ha−1) was used to create plots without termite activity next to plots with termite activity. The subplots consisted of Pennisetum pedicellatum mulch, wood Pterocarpus lucens mulch and composite (wood+straw) mulch, applied at rates of 3, 6 and 4 t ha−1, respectively. Two years after establishing the experiment, the combined effect of termite and mulch on the change in physical properties of the soil was measured. The parameters used for this assessment were porosity, saturated hydraulic conductivity and soil resistance to cone penetration. Soil water content was also measured. Termite activity was found to increase soil porosity, soil saturated hydraulic conductivity, improve soil water status and reduce soil bulk density and soil resistance to cone penetration. The only difference between bare plots and mulched plots without termites was in water content. This indicates that the mechanism whereby mulch improves the physical properties of crusted soil is mainly based on soil biology processes and to a limited extent on protecting soil against weather impact. © 1997 John Wiley & Sons, Ltd.

Soil Management and Topsoil Thickness Effects on Maize for Two Tanzanian Soils

ABSTRACT Field experiments were conducted at the research farm of the Sokoine University of Agriculture, Morogoro, Tanzania. The main objective of the study was to evaluate the impact of surface soil thickness and management practices on root distribution, plant nutrient content, soil moisture regime, and yield of maize (Zea mays). The experiment was located at two sites, Misufini and Mindu, with Haplic Lixisol and Haplic Acrisol soils, respectively. A detailed soil survey was done to determine four erosion classes based on thickness of the Ap horizon: A, least eroded with surface soil thickness of > 25 cm; B, slightly eroded with surface soil thickness of 21–25 cm; C, moderately eroded with surface soil thickness of 16–20 cm; and D, severely eroded with surface soil thickness of < 15 cm. Three management practices were applied in each erosion class: farmer's practice (control), tied ridges with no fertilizer, and tied ridges with farmyard manure (FYM). Observations on root growth and maize grain yield were made only for farmer's practice and tied ridges with FYM treatments. The root number decreased with depth, but increased with plant growth during the season. The highest number was observed in the moderately eroded class C at Misufini and severely eroded class D at Mindu site. The farmyard manure treatment produced the largest root number at all depths. Maize grain yield decreased with decreasing topsoil depth at both sites and the lowest yield was obtained in plots with topsoil depth of < 15 cm. The use of farmyard manure as a management practice produced significantly higher yields than farmer's practice. Root number was significantly correlated with grain yield for erosion class C at Mindu site, although a trend of increase in yield with increase in root number was observed for all erosion classes at both sites. Soil surface thickness significantly affected the ear leaf concentrations of N and P. The farmyard manure treatment had the highest concentration of P in plants at all stages. Soil moisture content was significantly higher in the farmer's practice treatment, which had low plant vigour. High soil moisture content was measured in the least eroded soils (erosion classes A or B) at both sites.

Classification of Soils on the Raised Coral Reef Terraces of Minami-Daito Island : I. Occurrence of Haplic Lixisol or Typic Rhodudalf in Japan

Classification of Soils on the Raised Coral Reef Terraces of Minami-Daito Island : I. Occurrence of Haplic Lixisol or Typic Rhodudalf in Japan

Characterization of cohesion, friction and sensitivity of two hardsetting soils from Zimbabwe

Hardsetting soils are defined as those which develop very high strength with little observable structure when they dry, but lose much of their strength when wet. Sandy loam soils (haplic lixisol) which showed typical hardsetting behaviour in the field were identified in a small-scale farming are in Zimbabwe. They were too hard to cultivate when dry, and produced a cloudy structure when plowed by a tractor in a slightly moist state. Samples of two sandy loam topsoils were collected, prepared at different water contents varying from saturated to field-dry and tested for stress-deformation and shear strength behavior in a direct shear box. For both soils at water contents above 10 g 100 g −1, the stress-deformation curves are of the plastic material type with continually increasing shear stress with deformation. At water contents less than 10 g 100 g −1, curves associated with more brittle material behavior resulted, with a peak shear stress reached at 3–4 mm deformation followed by a considerable loss in strength. At nearly all of the water contents, the angle of friction was 34–37° for both soils, but cohesion changed from nearly zero at saturation to well over 100 kPa in the field-dry state. The contribution of matric tension alone to soil cohesion is more than enough to account for the observed increases in strength on soil drying, and the potential role of soluble silicate cementing agents does not appear to be a factor in the case of these two soils.