Improvement of the physical fertility of a degraded Alfisol with planted and natural fallows under humid tropical conditions

Abstract. Topsoil (0–15 cm) bulk density, aggregate stability, soil dispersibility, water retention and infiltration were measured between 1989 and 1996 on an Alfisol under rehabilitation in southwestern Nigeria. The planted leguminous species were Pueraria phaseoloides, Senna siamea, Leucaena leucocephala, Acacia leptocarpa and A. auriculiformis. Also, plots with natural fallow and maize/cassava intercropping were included. Level (minimum) and mound tillage with hoes was adopted for the cultivated areas under study after 4 and 6 year fallow periods. Under fallow, the soil bulk density decreased from1.56 to 1.11 t m73.The continuously cropped treatment (level tillage) had significantly higher bulk density than the fallowed subplots after 6 years. Mean soil penetrometer resistance ranged from 75 to 157 kPa for fallowed plots and from 192 to 295 kPa for the continuously cropped (level tillage) subplot. Surface soilwater contentswere similar for all the treatments during the soil strength measurements. Although soil aggregates were generally of low stability and not well formed, they were improved by fallowing.
Soil structural improvement by planted fallows was similar to that by natural fallow, but the trees were more promising for long-term fallow (>6 years) than the herbaceous P. phaseoloides. However, the improvement in soil structure after 4 or 6 year fallow could not be maintained in subsequent cropping. Furthermore, the significant improvement in soil bulk density caused by A. auriculiformis and natural fallow was more rapidly lost on the cultivated subplots compared with other fallow treatments. Thus, soil structure recovery under a fallow does not imply a sustained improvement when stress is applied to this soil. Post-fallow soil management options such as residue incorporation and tillage to ameliorate compaction or soil strength will be necessary to enhance the improvements by fallow species.     

Plant nutrients in a degraded soil treated with water treatment sludge and cultivated with grasses and leguminous plants

The objective of this work was to evaluate rates for applications of water treatment sludge (WTS) as a nutrient source for grasses and leguminous plants cropped in a soil degraded by tin mining in the Amazon Region (Natural Forest of Jamari, Rondonia State, Brazil). The treatments consisted of three rates of nitrogen supplied by WTS (100, 150 and 200 mg kg⁻¹ soil), five combinations of plants, two controls (absolute control, without fertilization; and chemical control, soil+lime+chemical fertilizers). WTS modified the contents of macro and micronutrients in the degraded soil, but it was not, as used in the present study, sufficient for the rehabilitation of the degraded area.     

Influence of Potassium Fertilizer on Yield of Plantain Intercropped with Cassava on an Oxic Paleustalf in Southwestern Nigeria

Abstract

There is very little literature on the influence of plantain–cassava intercropped on this soil type. Therefore, an experiment was conducted in 1993 and 1995 cropping seasons on the influence of potassium (K) fertilizer on the yield of the two crops on a soil classified as Oxic paleustalf (or Ferric Luvisol) in the rain forest agroecological zone of Nigeria. Four rates of K fertilizer (120, 240, 360, and 480 kg K ha^?1) and control were evaluated on the yield and yield components of these two crops in sole and intercropping. The experimental design was a randomized complete block (RCBD) replicated four times. Results showed that the soil is acidic and the exchangeable cations contents were suboptimal when compared with the optimum required for a sustained cultivation of plantain. Furthermore, the plantain–cassava intercropped yields responded significantly (p<0.05) to fertilizer applied in terms of the yield and yield components of both crops in sole and intercropping. Highest bunch weight of plantain and tuber yield of cassava was recorded at 360 and 240 kg K ha^?1 (taking the mean of both years). Potassium fertilizer after this point resulted in lower yields of both crops when intercropped.     

Amelioration of a highly degraded tropical alfisol by planting I. Changes in soil physical and chemical properties 1989-91

This paper examines soil amelioration by planting 15 leguminous and graminaceous plant species, including herbaceous annuals, perennials and biennials, and woody perennials and biennials. Disturbed and undisturbed natural regrowth were planted with leguminous species, in some cases with fertilizer applied at planting (400 kg ha⁻¹ of 15:15:15 NPK). The studies were made on two highly degraded sites in southwestern Nigeria which had been subjected to intensive mechanized cropping for a period of 10 years. Changes in soil physical and chemical properties were monitored from 1989 to 1991. Acacia difficilis, Brachiaria lata and Mucuna utilis had the lowest survival rates by the following growing season. Soil fertility and compaction levels differed between sites. Planting had no effect on the latter. The decreases in compaction (i.e. macroporosity) between 0.00 and 0.10 m depth at both sites one month before and five and 17 months after planting were 43, 59 and 61 per cent, respectively were attributed to exclusion of heavy machinery from the sites. Large decreases in fertility occurred at both sites and were attributed to a combination of nutrient extraction and to leaching. Between fallow species, exchangeable Ca, pH and the cation-exchange capacity (CEC) were greater and total acids lower for herbaceous cover compared with woody perennials, and was attributed to a higher Ca demand by the latter. Highest and lowest values of Ca, CEC and pH occurred in plots where plant material was returned to the soil (i.e. by cutting or die-back) and in cropped plots, respectively. Natural regrowth was as effective or better than planted species in improving soil physical and chemical properties. Therefore the use of exotic plant species for ameliorating highly degraded alfisols is unnecessary. Amelioration of highly degraded alfisols may be best effected by allowing natural regrowth to occur while excluding all mechanized traffic from the site.     

炭化生活污水污泥对酸化红壤的改良效果

从南京市、马鞍山市和丹阳市的3个污水处理厂采集污泥,在500℃下热解制备炭化污泥,测定了污泥和炭化污泥的性质和重金属含量,研究了污泥和炭化污泥对酸性红壤改良效果,并探讨了炭化污泥中重金属的环境风险。结果表明,污泥和炭化污泥中含有一定量的碱,添加炭化污泥可提高红壤的p H和交换性钙、镁和钾含量,降低土壤交换性铝和交换性H+含量。但污泥中大量铵态氮的硝化作用释放质子,抵消了污泥对红壤酸度的改良作用。添加污泥和炭化污泥提高了土壤有机碳、有效磷和速效钾的含量,提高了土壤肥力。污泥炭化后重金属含量有所增加,但大部分重金属的有效态含量下降,说明热解过程可以降低部分有毒重金属的活性。与对照相比,添加炭化污泥会增加土壤中部分重金属有效态含量,特别是有效态锌含量显著增加,因此炭化污泥农业利用存在一定的环境风险。建议将炭化污泥用于酸化的森林红壤的改良。     

武汉市典型地区土系的研究

本文以典型区土壤详查和环境研究为基础 ,采用《中国土壤系统分类》(修订方案 1 995)的标准划分了土壤的高级分类单元 ;探讨了土系的划分原则、依据及土系的描述方法 ,并拟定了区域土系检索系统 .为土系的研究和土系制的应用提供范例     

Rehabilitation of degraded lands by means of fallowing in a semi-arid area of northern Nigeria

Land degradation in semi-arid regions of Nigeria is a very serious problem and therefore rehabilitation of degraded lands is essential. This article reports the results of an investigation which was carried out to assess the extent to which fallowing rehabilitates degraded lands in a semi-arid area in northern Nigeria. An inferential approach was used which involved side-by-side comparison of plots located within an area of uniform climatic, geologic and geomorphic characteristics, but which have been under fallow for different periods of time (2, 5, 10 or 15 years). Using a systematic sampling procedure, topsoil and subsoil samples were collected from each of the fallow plots and also from a plot under a plant community of well over 80 years of age which was chosen to serve as the control (fairly natural vegetation). The extent to which the land of each fallow plot had been rehabilitated could be assessed by comparison with the condition of the control plot. The samples were analysed for texture, bulk density, water-stable aggregates greater than 0.50 mm, moisture content, organic matter, pH, cation exchange capacity (CEC), total nitrogen, available phosphorus and exchangeable bases. An analysis of variance (ANOVA) technique was used to test for significant differences amongst the fallow plots, while Student's t-test was used to compare the mean values of the soil properties of the control with the same properties under each of the fallow plots. The results obtained varied considerably, but in general it was observed that there were decreases in the coarsening of soil texture and bulk density, but increases in other soil properties with increases in the length of the fallow period. However, the changes were generally found to be more significant under the older fallows (10 and 15 years) than under the newer fallows (2 and 5 years). The causes of these trends and their implication for sustainable land development in the area are discussed. It is concluded that for land rehabilitation to be effective in this area, either fallow times must be quite long, or ways of improving the soil's recuperative capacities under short-term fallow should be sought.     

Nutrient availability and cocoyam yield under different tillage practices

Research information on the effect of tillage systems on cocoyam (Xanthosoma sagittifolium (L.) Schott) growth, nutrient status and yield is lacking in Africa. The effects of zero tillage with mulch, zero tillage without mulch, manual mounding, manual ridging and conventional tillage on cocoyam yield, growth and nutrient availability were compared during 2 years on an Alfisol (Oxic Tropuldaf) at Owo in the rainforest zone of Nigeria. The surface soil (0–20 cm) was chemically analyzed before and after crop harvest and selected soil physical properties were determined. Concentration of soil organic C, N, P, K and Mg and the leaf N, P and K were significantly influenced (p = 0.05) by tillage, with zero tillage with mulch being the most effective treatment in conserving the fertility of the surface soil (0–20 cm). Soil fertility, as indicated by organic C, N, P, K, Ca and Mg, declined significantly (p = 0.05) over time in all tillage systems, but this decline was more pronounced in the conventional tillage. Zero tillage with mulch, zero tillage without mulch, manual mounding, manual ridging and conventional tillage reduced the soil organic C concentration by 20, 23, 23, 24 and 33%, respectively over the 2-year period. The decreases in soil N concentration were 25, 31, 31, 38 and 56%, soil P concentration were 13, 15, 17, 16 and 26%, and soil K concentration were 16, 26, 31, 37 and 53%, respectively. Tillage did not affect corm and cormel yields in the first year. In the second year, due to the elimination of ploughing, significant differences were obtained in the cormel yield but not of corm yield. In 2005, zero tillage with mulch produced the highest cormel yield (13.5 mg ha⁻¹) of cocoyam followed by zero tillage without mulch (13.2 mg ha⁻¹), manual mounding (12.7 mg ha⁻¹) and manual ridging (12.5 mg ha⁻¹). The lowest cormel yield (9.5 mg ha⁻¹) of cocoyam was produced by conventional tillage. Soil water contents in zero tillage with mulch and zero tillage without mulch were significantly higher (p = 0.05) than in the other tillage systems. Soil bulk density ranging from 1.21 to 1.40 mg m⁻³ correlated positively with leaf nutrient concentration and yield. Cocoyam can be grown successfully on zero tillage, with mulch and without mulch or minimum tillage systems on an Alfisol of the humid tropics.     

Amelioration of a calcareous saline-sodic soil by gypsum and forage plants

A field experiment was carried out at the University of Agriculture, Faisalabad (Pakistan) during 1988–90 to evaluate the comparative efficiency of chemical and biological methods for the reclamation of a calcareous saline-sodic soil (pHs

1 pHs = pH of saturated soil paste

= 8.2–8.6; ECe

2 ECe = Electrical conductivity of the saturation extract

= 7.4–9.0 dS m⁻¹; SAR

3 SAR = Sodium adsorption ratio

= 55.6–73.0 for upper 30 cm layer). Five treatments were assessed, three involved cropping: sesbania (Sesbania aculeata), sordan (Sorghum bicolor x Sorghum sudanese), and kallar grass (Leptochola fusca) and two were non-cropped (control and gypsum at 100.0 per cent GR-15·0 cm) were employed. Water of low electrolyte concentration (EC = 0.27 dS m⁻¹) was used for irrigation and leaching. Sesbania and kallar grass were found to be effective biotic materials for soil reclamation. These plant species produced substantial biomass and also improved the soil environment by lowering the EC and SAR of the soil. Sordan was relatively less-effective due to its sensitivity to high temperature and sodicity during germination and early seedling stages. After two cropping seasons, wheat (cultivar LU 26S) was sown as a test crop. Efficiency of treatments as indicated by wheat grain yield was in the order: sesbania = gypsum > kallar grass > sordan > control.     

The Role of Soil Mineralogical Characteristics in Sustainable Soil Fertility Management: A Case Study of Some Tropical Alfisols in Nigeria

The pedogenic horizons of nine profile pits dug across three toposequences were studied to determine the soil mineralogical characteristics and its implications on sustainable management of the fertility of some tropical Alfisols in Nigeria. Results showed that the epipedon which were predominantly ochric had textures that ranged from sand to sandy loam, while the subsurface (B/Bt) horizons had sandy clay loam to sandy clay texture and were gravelly (31.79–83.04%). The soil reaction ranged from strongly acid to neutral (pH 5.10 to 7.05). Calcium and magnesium dominated the exchange sites and accounted for about 75% of the exchangeable bases. Illite/mica and kaolinite were the dominant minerals in the clay fractions, while quartz, mica, and feldspars dominated the fine sand and silt fractions of the soils. While the presence of illite and mica could be important for potassium nutrition in these soils, kaolinite and oxides of iron could also cause phosphorus fixation.     

A winter intercrop of faba bean and rapeseed for silage as a substitute for Italian ryegrass in rotation with maize

In order to combine the ability of legumes to fix atmospheric nitrogen and the cruciferous capacities to mobilize soil nutrients and herbicide action, the aim of this work was to evaluate an alternative winter intercrop (faba bean-rapeseed) as a replacement of Italian ryegrass culture in a rotational system with maize as summer crop. For this purpose, two adjacent plots were used during three agronomic years (2011–2012, 2012–2013 and 2013–2014) to evaluate the agronomic performance through the forage production, nutritional composition of forage and silage, and the effects on soil fertility. The Italian ryegrass was cultivated under conventional management: using chemical fertilization and recommended dosages of herbicides. The faba bean-rapeseed intercrop was cultivated under an alternative management: organic fertilization and less herbicide supply. The intercrop provides higher forage yield per hectare than Italian ryegrass, with greater protein (kg ha^?1) and similar energy (GJ ha^?1) yields. The intercrop allows reducing the inputs of chemical fertilization and herbicides, and it has a positive effect on the balance of soil nutrients, especially increasing the potassium, calcium and magnesium contents. The results show that faba bean-rapeseed intercrop could be an alternative to the Italian ryegrass as winter crop.     

休耕和种植作物对黑麻土壤肥力的影响

为了明确不同茬口土壤养分的固持残留水平,建立高效合理的轮作顺序以解决连作再植障碍问题。2018年在甘肃定西渭源县莲峰镇绽坡村随机区组设计、“S”形取样休耕1季、种植1季春小麦、马铃薯、蒙古黄芪和当归后0-20 cm层次的黑麻土壤,测定土壤全量、速效养分和阴阳离子含量。结果表明:休耕1季和种植1季蒙古黄芪增加了0-20 cm层次土壤的有机质、全氮、速效磷、速效钾、阴阳离子、Mg^2+、SO4^2-和Cl^-含量,种植1季当归降低了0-20 cm层次土壤的有机质、全氮、速效磷、速效钾、阴阳离子、Mg^2+、SO4^2-和Cl^-含量。方差分析显示,休耕1季和种植1季蒙古黄芪后0-20 cm层次黑麻土壤的有机质、全氮、速效磷、速效钾、阴阳离子、Mg^2+、SO4^2-和Cl^-含量显著高于种植1季当归。主成分回归分析发现,休耕1季和种植1季蒙古黄芪后0-20 cm层次黑麻土壤肥力综合指数为0.98和0.56,种植1季当归的综合指数得分仅为0.07。休耕1季是黑麻土壤用养结合的简便有效方法,种植1季蒙古黄芪是培肥黑麻土壤肥力的适宜作物。     

Impact of long-term application of fertilizer, manure and lime under intensive cropping on physical properties and organic carbon content of an Alfisol

Intensive cropping with conventional tillage results in a decline of soil organic carbon (SOC) with consequent deterioration of soil physical properties. Some studies indicate that this decline in SOC can be arrested by way of organic manure application and improved nutrient management practices. This study was conducted to find out the long-term effects of inorganic fertilizer, manure and lime application on organic carbon content and physical properties of an acidic Alfisol (Typic Haplustalf) under an annual soybean-wheat crop rotation. Six treatments namely, control (CON), nitrogen fertilization (NIT), nitrogen and phosphorus (NP), nitrogen, phosphorus and potassium (NPK), NPK plus manure (NPKM) and NPK plus lime (NPKL) from a long-term fertilizer experiment continuing at Ranchi, India, were chosen for this study. Soil samples were collected from the selected treatments after 29 crop cycles and analyzed for physical and chemical properties. The results indicated that SOC content in all the treatments decreased from initial levels, but the decrease was considerably less in NPKM (8.7%) and NPKL (10.9%) treatments than that in NIT (28.3%) treatment. The SOC at 0-15 and 15-30 cm depth was lowest in NIT and CON. The NPKM, NPKL and NPK treatments up to 30 cm soil depth recorded significantly higher SOC than NIT and CON. Application of balanced fertilizer along with manure (NPKM) or lime (NPKL) improved soil aggregation, soil water retention, microporosity and available water capacity and reduced bulk density of the soil in 0-30 cm depth over CON. In contrast, soil aggregate stability, microporosity and available water capacity were significantly lower in the NIT plots than that in CON. The study thus suggests that soil management practices in acidic Alfisols should include integrated use of mineral fertilizer and organic manure or lime to maintain the organic carbon status and physical environment of soil.     

Amelioration of sodic soils by trees for wheat and oat production

Prolonged occupation of sodic soils by trees results in the latters' amelioration in terms of decreased pH and electrical conductivity and improved organic matter and fertility status. To assess whether sodic soils reclaimed by tree plantations can be used for growing agricultural crops, a greenhouse pot trial was conducted during winter of 1994–95 (November–April) at the Central Soil Salinity Research Institute, Karnal, India. Wheat (Triticum aestivum, L; cultivar HD 2329) and oat (Avena sativa, L. cultivar local) plants were grown in topsoils (30 cm) collected from 24-year-old plantations of Prosopis juliflora, Acacia nilotica, Eucalpytus tereticornis, Terminalia arjuna and Albizia lebbek that had been established in 1970 on a highly sodic soil (pH₂ 10·2–10·5), and a reclaimed sodic soil from a farm field adjacent to the plantations. The organic carbon content and nutrient status of the soil under the 24-year-old plantations was much higher than that of a reference farm soil reclaimed through gypsum in 1974. Soil amelioration was highest under Prosopis canopies (pH 7·4 and organic carbon 0·89 per cent) in topsoil and minimum in Eucalpytus canopies (pH 8·6 and organic carbon 0·56 per cent). Reduced sodicity and improved fertility resulted in much better growth reference and productivity of the wheat and oat test crops grown on the five plantation soils, than in the reference farm soil. Grain and straw yields of wheat and oats were maximum in Prosopis soil (wheat 61·7 g grains and 87·5 g straw and oats 87·9 g grains and 111·1 g straw per pot) and minimum in Eucalpytus soil (32·3 and 25·3 g, and 42·7 and 58·5 g per pot). Grain yields of both wheat and oats obtained in the Prosopis soil were 4·5 and 3·5 times more, respectively, than obtained in the reference farm soil. The phosphorus concentration in whole plant tissues of wheat and oats was highest in Prosopis soils reflecting the prevailing phosphorus status and better restoration processes of the soils. Potassium concentration was little affected due to different soil treatments. The study clearly indicated that prolonged afforestation of sodic soils by tree plantations, particularly by Prosopis and Acacia trees, may restore the productivity of abandoned soils to much above the present agricultural production levels. The results further suggest that 24 years' occupation of sodic soils by trees, such as Prosopis, Acacia, Eucalyptus, Terminalia and Albizia, did not result in a build-up or accumulation of toxic allelochemicals which could be injurious to wheat and oats cultivation on such soils. © 1998 John Wiley & Sons, Ltd.     

应用水解聚丙烯腈改良黄绵土的效果研究

该文通过采用土壤结构改良剂水解聚丙烯腈处理黄绵土，以探讨幼林地土壤管理的有效措施，试验结果表明：土壤结构改良黄绵土的效果非常显著。它的使用促进了团粒结构的形成，降低土壤容重，提高土壤渗透性，而且在浓度为０．０５％￣０．４０％的范围内，对黄绵土的改良效果随其浓度的增大而升高。还初步表明：幼林地使用土壤结构改良剂，可提高土壤水分，因此，在劣质立地幼林抚育管理中应用土壤结构改良剂是适宜的。     

Agricultural and ecological aspects of a sandy soil as affected by the application of municipal solid waste composts

We present the results of a plot experiment in which the changes in physical, chemical and physico-chemical properties of a sandy soil were examined after amending the soil with two different composts produced from municipal solid wastes. Triticale (X Triticosecale), cultivated in a 3-y monoculture, was used as a test plant. Both composts differed in their concentrations of heavy metals. Composts were applied non-recurrently in the spring before sowing, at the rates of 18, 36, and 72 t dry matter ha⁻¹. The plots without fertilization, and those fertilized annually with mineral nitrogen (N), phosphorous (P), and potassium (K) were used as controls. Soil samples were collected 1 month after compost application, as well as each year after harvesting. Application of both composts improved soil physical properties, associated with increasing content of organic carbon (OC). Statistically significant increases of total porosity, field water capacity and amounts of plant-available water were found only in the short time after compost application. Despite the fact that soil OC content decreased with time, a C:N ratio clearly increased in the third year after compost application, which was explained by a depletion of N reserve. Both composts caused a large increase of plant-available P, K, and magnesium (Mg), which was observed during the entire period of the experiment. Beneficial changes were also observed in soil humic substances composition. These were confirmed by increased humic acids content and humic/fulvic acid ratios. Soil cation exchange capacity and base saturation increased in all plots amended with composts. This effect was still observed 1 year after compost application, while in the third year it remained significant only at the highest compost rates. Compost originating from industrial areas, even if applied in low amounts, caused a significant increase in total concentration of soil heavy metals. This fact did not result, however, in any substantial changes in soil quality with regard to heavy metals content.     

Management of a previously eroded tropical Alfisol with herbaceous legumes: Soil loss and physical properties under mound tillage

A study was carried out on a previously eroded Oxic Paleustalf in Ibadan, southwestern Nigeria to determine the extent of soil degradation under mound tillage with some herbaceous legumes and residue management methods. A series of factorial experiments was carried out on 12 existing runoff plots. The study commenced in 1996 after a 5-year natural fallow. Mound tillage was introduced in 1997 till 1999. The legumes – Vigna unguiculata (cowpea), Mucuna pruriens and Pueraria phaseoloides – were intercropped with maize in 1996 and 1998 while yam was planted alone in 1997 and 1999. This paper covers 1997–1999. At the end of each year, residues were either burned or mulched on respective plots. Soil loss, runoff, variations in mound height, bulk density, soil water retention and sorptivity were measured. Cumulative runoff was similar among interactions of legume and residue management in 1997 (57–151 mm) and 1999 (206–397 mm). However, in 1998, cumulative runoff of 95 mm observed for Mucuna-burned residue was significantly greater than the 46 mm observed for cowpea-burned residue and the 39–51 mm observed for mulched residues of cowpea, Mucuna and Pueraria. Cumulative soil loss of 7.6 Mg ha⁻¹ observed for Mucuna-burned residue in 1997 was significantly greater than those for Pueraria-mulched (0.9 Mg ha⁻¹) and Mucuna-mulched (1.4 Mg ha⁻¹) residues whereas in 1999 it was similar to soil loss from cowpea treatments and Pueraria-burned residue (2.3–5.3 Mg ha⁻¹). There were no significant differences in soil loss in 1998 (1–3.2 Mg ha⁻¹) whereas Mucuna-burned residue had a greater soil loss (28.6 Mg ha⁻¹) than mulched cowpea (6.9 Mg ha⁻¹) and Pueraria (5.4 Mg ha⁻¹). Mound heights (23 cm average) decreased non-linearly with cumulative rainfall. A cumulative rainfall of 500 mm removed 0.3–2.3 cm of soil from mounds in 1997, 3.5–6.9 cm in 1998 and 2.3–4.6 cm in 1999, indicating that (detached but less transported) soil from mounds was far higher than observed soil loss in each year. Soil water retention was improved at potentials ranging from −1 to −1500 kPa by Mucuna-mulched residue compared to the various burned-residue treatments. Also, mound sorptivity at −1 cm water head (14.3 cm h^−1/2) was higher than furrow sorptivity (8.5 cm h^−1/2), indicating differences in hydraulic characteristics between mound and furrow. Pueraria-mulched residues for mounds had the highest sorptivity of 17.24 cm h^−1/2, whereas the least value of 6.96 cm h^−1/2 was observed in furrow of Mucuna-burned residue. Pueraria phas eoloides was considered the best option for soil conservation on the previously eroded soil, cultivated with mound tillage.     

Decomposition of straw in relation to tillage,moisture, and arthropod abundance in a semi-arid tropical Alfisol

The decomposition of rice straw was studied in relation to straw moisture and the abundance of soil arthropods, such as Acarina, Collembola, and miscellaneous groups dominated by termites [Odontotermes obesus (Rambur) and Microtermes obesi Holmgren], across tillage treatments (no tillage, shallow tillage, and deep tillage) in Alfisols of the semi-arid tropics in India from August 1989 to July 1990. In the straw, across the treatments, Acarina were dominant (>70% of the total arthropods), and Collembola were a minor component. O. obesus and M. obesi foraged straw together under the cover of an earthern sheet. A larger number of arthropods was recorded during the rainy season, but they were either negligible or absent during the dry season. The abundance of arthropods and mass loss of straw was greater in coarse-mesh bags than in the fine-mesh bags. Their abundance was significantly affected by tillage treatments and season (P<0.01). In the beginning, it was significantly greater in the no-tillage and shallow-tillage than in the deep-tillage treatment. The mass loss was 46% of the initial mass during the first 60 days, and more than 90% after 330 days of decomposition. Tillage had a significant effect on mass loss, particularly after 330 days, and the no tillage treatment led to a greater mass loss. Multiple linear regression analysis revealed that the moisture content of the straw and the abundance of arthropods had significantly affected the mass loss in both fine-and coarse-mesh bags across the tillage managements.Visiting Scientist (under the Rockefeller Foundation Environmental Research Fellowship in International Agriculture) in Resource Management Program at ICRISAT, India     

Chemical and microbial properties of semiarid tropical soils of short-term fallows in Burkina Faso,West Africa

In the soudano–sahelian zone of Burkina Faso, the short-term fallow effect on the soil chemical and microbial properties was evaluated. In four farm experiments, two types of fallows were compared with cultivated fields: a natural vegetation fallow and a fallow enriched with Andropogon gayanus. After 5 to 7 years of experiments, soil chemical and microbial characteristics were determined in laboratory for 0–10 cm soil depth. Soil organic carbon (+64%), nitrogen (+35%), microbial biomass (+76%), basal respiration (+141%), and β-glucosidase activity (+86%) were significantly higher in fallows plots than in cultivated fields. The metabolic quotient was not significantly different on fallows compared to the cropped plots. Also, no significant difference was highlighted between natural vegetation fallows and the A. gayanus-enriched one.