Long-term integrated soil fertility management in South-western Nigeria: Crop performance and impact on the soil fertility status

Crop response, tree biomass production and changes in soil fertility characteristics were monitored in a long-term (1986–2002) alley-cropping trial in Ibadan, Nigeria. The systems included two alley cropping systems with Leucaena leucocephala and Senna siamea on the one hand and a control (no-trees) system on the other hand, all cropped annually with a maize–cowpea rotation. All systems had a plus and minus fertilizer treatment. Over the years, the annual biomass return through tree prunings declined steadily, but more drastically for Leucaena than for Senna. In 2002, the nitrogen contribution from Leucaena residues stabilized at about 200 kg N/ha/year, while the corresponding value for Senna was about 160 kg N/ha/year. On average, the four Leucaena prunings were more equal in biomass as well as in amounts of N, P and cations, while the first Sennapruning was always contributing up to 60% of the annual biomass or nutrient return. Maize crop yields declined steadily in all treatments, but the least so in the Senna + fertilizer treatment where in 2002 still 2.2 tonnes/ha of maize were obtained. Nitrogen fertilizer use efficiency was usually higher in the Senna treatment compared to the control or the Leucaena treatment. Added benefits due to the combined use of fertilizer N and organic matter additions were observed only for the Sennatreatment and only in the last 6 years. At all other times, they remained absent or were even negative in the Leucaenatreatments for the first 3 years. Most chemical soil fertility parameters decreased in all the treatments, but less so in the alley cropping systems. The presence of trees had a positive effect on remaining carbon stocks, while they were reduced compared to the 1986 data. Trees had a positive effect on the maintenance of exchangeable cations in the top soil. Exchangeable Ca, Mg and K – and hence ECEC – were only slightly reduced after 16 years of cropping in the tree-based systems, and even increased in the Senna treatments. In the control treatments, values for all these parameters reduced to 50% or less of the original values after 16 years. All the above points to the Senna-based alley system with fertilizers as the more resilient one. This is reflected in all soil fertility parameters, in added benefits due to the combined use of fertilizer nitrogen and organic residue application and in a more stable maize yield over the years, averaging 2.8 tonnes/ha with maximal deviations from the average not exceeding 21%.     

种植Bt玉米对土壤微生物活性和肥力的影响

在温室种植比较了美国Bt玉米(34B2 4 (Mon810 ) )与同源常规玉米(34B2 3)、中国Bt玉米(12 4 6×14 82 (Cry1A) )与常规玉米(农大3138)对土壤微生物活性和肥力的影响。结果表明,两个Bt玉米品种5次取样(2 5、39、5 3、6 7、82 d)的根际土壤中都能检测到Bt蛋白,含量在2 0～80 ng·g- 1 dry soil之间。4个处理土壤硝化作用和精氨酸氨化作用强度在所有取样时期均没有显著差异;土壤蔗糖酶、土壤蛋白酶和酸性磷酸酶活性则分别只在2 5 d(农大3138<34B2 4与12 4 6×14 82 )、6 7d(34B2 4 >12 4 6×14 82和农大3138)和6 7d(34B2 4 >其它3个处理)存在显著差异;土壤脱氢酶、土壤脲酶和土壤呼吸强度则在多数取样时期多个处理间存在显著差异,说明其与玉米品种特性关系密切,其中,土壤脱氢酶和脲酶活性的差异在两个Bt玉米品种、Bt与同源常规品种(34B2 4与34B2 3)、Bt与常规品种(12 4 6×14 82与农大3138)以及常规与常规品种(34B2 3与农大3138)之间均没有一致的规律,但34B2 4与34B2 3处理的土壤呼吸作用强度高于12 4 6×14 82与农大3138,说明种植该系列品种的土壤中微生物总活性较高、土壤代谢旺盛。82 d后4个处理土壤有机质、NPK全量与速效养分含量均没有显著差异。本试验观测期种植Bt玉米并没有导致土壤微生物活性和土     

Addition of a volcanic rockdust to soils has no observable effects on plant yield and nutrient status or on soil microbial activity

Background and Aims

Rising costs and pressure on supplies of commercial mineral fertilizers and increasing markets for organically produced foods and feeds have led to a growing interest in soil amendments to supply plant nutrients. Rockdust is a by-product of quarrying and its effectiveness to supply plants with nutrients has been a contested issue and there have been no assessments of its effect on soil biota other than plants. The aim of this study was to assess the effect of a commercially-available volcanic rockdust application on crop growth and element concentrations for a wide range of macro and microelements and the response of soil microbial communities to rockdust due to the potential alteration in soil mineralogy.

Methods

A three-year controlled outdoor-growing experiment was conducted on three different soil types with two wheat cultivars in the first year following rockdust application and with forage species in the third year.

Results

Our results show that the tested rockdust had no positive or negative effect on plant growth or nutrient composition. In addition, the microbial response to added substrates, a sensitive measure of changes in soil environment, were unaltered by the rockdust.

Conclusions

As the rockdust had no nutrient or toxic effect it can probably be considered as an inert material which at least causes no harm but equally has no demonstrable ecological or agricultural benefit.     

Long-term effect of re-vegetation on the microbial community of a severely eroded soil in sub-tropical China

The long-term (18 years) effects of re-vegetating eroded soil on soil microbial biomass, community structure and diversity were investigated in a forest soil derived from Quaternary clay in the Red Soil Ecological Experimental Station of the Chinese Academy of Sciences. Large areas of land in this region of China have been subjected to severe soil erosion, characterised by the removal of the fertile surface soil and even the exposure of parental rock in some areas due to a combination of deforestation and heavy rainfall. The effects of planting eroded or uneroded soil with Pinus massoniana, Cinnamomum camphora or Lespedeza bicolor on the soil microbial community and chemical properties were assessed. Total soil microbial community DNA was extracted and bacterial 16 S rRNA gene fragments were amplified by PCR and analysed by terminal restriction fragment length polymorphism (T-RFLP). Microbial biomass carbon (C_mic) was measured by chloroform fumigation-extraction. Following the restoration there were significant increases in both C_mic and bacterial diversity (Shannon index), and significant changes in bacterial community structure. Erosion factors were significant only in minor dimensions suggesting that the restoration had been largely successful in terms of bacterial community structure. Compared with uneroded soil, C_mic recovered in L. bicolor and P. massoniana restored eroded plots and was significantly greater under these tree species than C. camphora, although soils in C. camphora restored plots displayed the highest bacterial diversity. The recovery of microbial biomass and diversity in the eroded plots was, to large extent, accompanied by the development of the same bacterial community structure as in the uneroded plots with erosion having relatively little effect on bacterial community structure.     

蚯蚓对土壤微生物及生物肥力的影响研究进展

蚯蚓被称为“生态系统工程师”,可以通过改善微生境(排粪、作穴、搅动)、提高有机物的表面积、直接取食、携带传播微生物等方式影响土壤微生物结构、组成和功能.蚯蚓活动形成的大孔隙(洞穴)、中、微空隙(排泄物)可以增加土壤孔隙度和通气性,有助于改善微生物微环境,促进其生长和繁殖.蚯蚓还通过取食、粉碎、混合等活动使复杂有机质转变为微生物可利用的形式,增加土壤微生物与有机质的接触面积,促进微生物对有机质的矿化作用,对土壤中碳、氮、磷养分循环等关键过程产生影响,最终促进土壤养分循环和周转速率,提高土壤生物肥力.     

Interactive effects of soil fertility and herbivory on Brassica nigra

Soil nutrient availability may affect both the amount of damage that plants receive from herbivores and the ability of plants to recover from herbivory, but these two factors are rarely considered together. In the experiment reported here, I examined how soil fertility influenced both the degree of defoliation and compensation for herbivory for Brassica nigra plants damaged by Pieris rapae caterpillars. Realistic levels of defoliation were obtained by placing caterpillars on potted host plants early in the life cycle and allowing them to feed until just before pupation on the designated plant. Percent defoliation was more than twice as great at low soil fertility compared to high (48.2% and 21.0%, respectively), even though plants grown at high soil fertility lost a greater absolute amount of leaf area (38.2 cm² and 22.1 cm², respectively). At both low and high soil fertility, total seed number and mean mass per seed of damaged plants were equivalent to those of undamaged plants. Thus soil fertility did not influence plant compensation in terms of maternal fitness. However, the pathways used to achieve compensation in seed production were different at low and high soil fertility. At low soil fertility, relative leaf growth rates (area added per inital area per day) of damaged plants were drastically reduced over the second week of caterpillar feeding. Damaged plants recovered the leaf area lost to herbivory in the two weeks following insect removal by increasing leaf relative growth rates above the levels seen for undamaged plants, but the replacement of leaf tissue lost to herbivory came at the expense of stem biomass. At high soil fertility, relative leaf growth rates of damaged plants were similar to those of undamaged plants both over the second week of caterpillar feeding and following caterpillar removal, and stem biomass was not affected by herbivory. These results suggest that higher levels of soil nutrients increased the ability of plants to stay ahead of their herbivores as they were being eaten. Because damaged plants at high soil fertility were able to maintain leaf growth rates to a greater extent than damaged plants at low soil fertility, they did not fall as far behind undamaged plants over the period of insect feeding and did not have as much catching up to do after feeding ended to compensate for herbivory.     

长期土壤肥力因子变化及其与植被指数耦合关系

以广西南宁、崇左地区作为典型区,利用AVHRR和MODIS NDVI遥感影像数据,以及1981年、2011年的土壤数据,分析归一化差异植被指数(NDVI)与土壤肥力因子及其变化之间的相互关系.结果表明:近30年来,土壤pH极显著下降,全氮、速效磷、速效钾含量显著上升;同时,NDVI变化整体呈现缓慢上升趋势,且NDVI变化与土壤有机质变化及土壤全氮变化呈显著正相关.因此,NDVI时间序列数据能够在一定程度上反映土壤有机质和土壤全氮含量的变化,这为土壤肥力长期变化监测提供了一种可行的方法.     

Potato-legume intercropping on a sloping terrain and its effects on soil physico-chemical properties

Plant and Soil - The objective of this paper was to develop a method based on infrared spectroscopy to compare mineral content in soils and apply it to evaluate soil mineralogical variations in...     

Temporal variations in some plant and soil P pools in two pasture soils of widely different P fertility status

Temporal variations in plant production, plant P and some soil P (and N) pools were followed over 21 months in two New Zealand pasture soils of widely different P fertility status. Plant growth rates, and herbage composition at the high-fertility site, were closely linked to soil water use, with growth rates falling when soil water deficits exceeded 60 mm. Herbage P concentrations reflected P fertility, and varied with season, being generally higher in winter and lower in summer. A similar temporal pattern was also observed for labile organic P (NaHCO₃-extractable P₀) in both soils. In the low-fertility soil in spring, net mineralization was especially strong, but from early winter net immobilization occurred. Surprisingly, Olsen P also changed temporally in the high-fertility soil. The microbial biomass remained fairly constant throughout the year, whereas the P content of the biomass varied seasonally. Although microbial biomass was not a useful index of soil fertility, highest microbial P₀ contents coincided with periods of maximum labile P₀ mineralization, when herbage production was also at a peak. Net N-mineralization in the low-fertility soil, in contrast to the high-fertility soil, was low but varied seasonally, under standardised incubation conditions. Soil P and N dynamics were apparently synchronised in the low-fertility soil through soil microbial processes, with mineral N being negatively correlated with microbial P₀ in samples collected two months later. The results of this investigation suggest that the demands of rapid and sustained pasture growth in spring and early summer can best be met by maximising the build-up of organic matter during the preceding autumn and winter. This practice could help to alleviate the common problem of feed shortage in North Island hill country pastures in late winter-early spring.     

红壤酶活性与肥力的关系

对供试红壤的基本化学性质、微生物量以及酶活性进行分析.结果表明,红壤脲酶、蔗糖酶、磷酸酶及过氧化氢酶与土壤有机碳、全氮及全磷显著相关或极显著相关,这些酶活性反映了红壤肥力水平的差异.土壤酶活性聚类分析结果与根据土壤化学、生物学性质所得结果基本相似.酶活性可用于评价红壤肥力质量.新鲜土样的酶活性不仅高于风干土样,且与土壤肥力质量联系更为密切.     

Insecticidal effects on soil microorganisms and their biochemical processes related to soil fertility

Among the four insecticides under study, hexachlorocyclohexane (BHC) followed by phorate significantly stimulated the populations of (total) bacteria, actinomycetes, fungi, aerobic non-symbiotic N2-fixing bacteria and P-solubilizing microorganisms in soil. Carbofuran significantly stimulated total as well as N2-fixing bacteria. Fenvalerate had no effect on P-solubilizers. All the insecticides stimulated the proportion of Penicillium in soil. Similarly, Pseudomonas with BHC, Sarcina with phorate, Corynebacterium, Azotobacter and Streptomyces with fenvalerate were also stimulated. On the other hand, Erysipelothrix with BHC, Staphylococcus with phorate, Staphylococcus, Nocardia and Fusarium with fenvalerate were inhibited. Almost all the insecticides reduced the proportions of Micrococcus and Rhizopus in soil. Insecticides also augmented the non-symbiotic N2-fixing and P-solubilizing capacities of the soil and the augmentation was more pronounced with BHC followed by phorate.     

间作豆科作物对山药田土壤化学和生物学性质的影响

采用田间小区试验方法,探讨了山药与苜蓿和三叶草两种豆科绿肥作物间作对土壤化学性质和生物学性质以及土壤综合肥力的影响.结果表明: 与山药单作相比,间作苜蓿和三叶草提高了0～20 cm和20～40 cm土层硝态氮、速效磷和速效钾含量,降低了山药根茎膨大初期和膨大盛期土壤pH和电导率.间作有助于提高山药整个生育期0～20 cm和20～40 cm土层土壤脲酶、碱性磷酸酶和过氧化氢酶活性以及土壤呼吸,但对蔗糖酶和脱氢酶活性影响不明显.采用隶属函数模型和主成分分析相结合的方法对间作山药收获期的土壤肥力进行综合分析,结果表明,间作两种豆科作物均具有显著提高山药田0～20 cm和20～40 cm土层土壤综合肥力的效果.通过间作豆科绿肥作物增加山药田的生物多样性是培肥山药田土壤、改善山药田土壤生态环境、缓解连作障碍的有效途径.     

Long-term maize-Desmodium intercropping shifts structure and composition of soil microbiome with stronger impact on fungal communities

Plant and Soil - Push–pull is an intercropping technology that is rapidly spreading among smallholder farmers in&nbsp;Sub-Saharan Africa. The technology intercrops cereals with Desmodium...     

Long-term effects of mineral versus organic fertilizers on activity and structure of the methanotrophic community in agricultural soils

Agricultural practices, such as mineral nitrogen fertilization, have an impact on the soil's ability to oxidize methane, but little is known about the shifts in the methanotrophic community composition associated with these practices. Therefore, the long-term effect of both mineral (NH4NO3) and organic (manure and GFT-compost) fertilizer applications on the soil methanotrophic community activity and structure were investigated. Both high and low affinity methane oxidation rates were lower in the soil treated with mineral fertilizer compared to the other soils. An enhanced nitrate concentration was observed in the mineral fertilized soil but nitrate did not show a direct affect on the high affinity methane oxidation. In contrast, the low affinity methane oxidation was slowed down by increased nitrate concentrations, which suggests a direct effect of nitrate on low affinity methane oxidation. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments specific for methanotrophs revealed a distinct community between the mineral and organic fertilized soils as extra Type I methanotrophic bands (phylotypes) became visible in the organic fertilized soils. These phylotypes were not visible in the patterns of the added organic fertilizers suggesting an indirect effect of the organic fertilizers on the methanotrophic community. Additionally, a molecular analysis was performed after the low affinity methane oxidation test. The enhanced methane concentrations used in the test enriched certain low affinity methanotrophs in the organic fertilized soils but not in the mineral fertilized soil. Supporting the molecular and functional observations, fatty acids characteristic for methanotrophs were less abundant in the soil treated with mineral fertilizer compared to the soil treated with compost. In conclusion, the function and molecular and chemical composition of the methanotrophic community are all altered in soil fertilized with mineral fertilizer.     

Dairy manure and tillage effects on soil fertility and corn yields

Organic amendments have received renewed attention to improve soil fertility for crop production. A randomized complete block split plot experiment was conducted to evaluate the dairy manure (DM) amendments of soil for corn (Zea mays L. cv. Monsanto 919) production under different tillage systems. Main plot treatments were no-till (NT), conventional tillage (CT), and deep tillage (DT), and subplot treatments were chemical fertilization (DM(0)), and DM at 10Mgha(-1)yr(-1) (DM(10)) and 20Mgha(-1)yr(-1) (DM(20)) with supplemental chemical fertilization. Results show that tillage and DM had significantly reduced bulk density (rho(b)) with greater porosity (f(t)) and hydraulic conductivity (K(fs)) than soils under NT and DM(0). Manuring was effective to improve soil physical properties in all tillage treatments. While manure significantly increased C sequestration, the N concentration was influenced by both tillage and manure with significant interaction. The CT significantly increased P as did the addition of manure. However, with manure, K was significantly increased in all tillage treatments. While tilled soils produced taller plants with higher grain yields, and water-use efficiency than NT soils, manuring, in contrast, increased corn harvest index. Manure exerted significant quadratic effect on corn biomass N and K uptake. The variable effects of tillage and dairy manuring on soil properties and corn growth are most probably related to "transitional period" in which soil ecosystems may have adjusting to a new equilibrium.     

西藏中部地区退化土壤秸秆还田的微生物变化特征及其影响

于西藏中部地区秸秆还田条件下,研究了土壤微生物区系及其主要生理类群的变化特征和土壤微生物对土壤肥力的影响及其相互关系。结果表明,不同秸秆还田方式,特别是秸秆覆盖和高茬方式较高的土壤水分、土壤温度及其耦合效应,为土壤微生物繁殖与活动提供了重要的土壤环境保障,有助于以细菌为主导的各类土壤微生物的相对均衡生长,对加速土壤有机残体分解,大幅度提高土壤有机质含量,促进土壤团粒结构形成和土壤养分转化均具重要作用,表明在西藏中部生态条件下,退化土壤具有在相对较短时间内实现结构重建与肥力恢复的可能性及其潜力。     

Biochar amendment to soils with contrasting organic matter level: effects on N mineralization and biological soil properties

Four biochar types, produced by slow pyrolysis of poultry litter (PL) and pine chips (P) at 400 or 500 °C, were added to two adjacent soils with contrasting soil organic matter (SOM) content (8.9 vs. 16.1 g C kg^?1). The N mineralization rate was determined during 14‐week incubations and assessments were made of the microbial biomass C, dehydrogenase activity, and the microbial community structure (PLFA‐extraction). The addition of PL biochars increased the net N mineralization (i.e., compared to the control treatment) in both soils, while for treatments with P biochars net N immobilization was observed in both soils. Increasing the pyrolysis temperature of both feedstock types led to a decrease in net N mineralization. The ratio of Bacterial to Fungal PLFA biomarkers also increased with addition of biochars, and particularly in the case of the 500 °C biochars. Next to feedstock type and pyrolysis temperature, SOM content clearly affected the assessed soil biological parameters, viz. net N mineralization or immobilization, MBC and dehydrogenase activity were all greater in the H soil. This might be explained by an increased chance of physical contact between the microbial community activated by SOM mineralization upon incubation and discrete biochar particles. However, when considering the H soil's double C and N content, these responses were disproportionally small, which may be partly due to the L soil's, somewhat more labile SOM. Nonetheless, increasing SOM content and microbial biomass and activity generally appears to result in greater mineralization of biochar. Additionally, higher N mineralization after PL addition to the H soil with lower pH than the L soil can be due to the liming effect of the PL biochars.     

不同水稻栽培模式下小麦秸秆腐解特征及对土壤生物学特性和养分状况的影响

采用尼龙网袋法于2007-2008年连续2a在水稻常规栽培和节水灌溉栽培模式下,研究小麦秸秆腐解特征、养分释放规律及对土壤微生物数量、酶活性和养分状况的影响.结果表明:秸秆还田后,在0-30d腐解较快,后期腐解速率逐渐变慢.90d时累计腐解率达到了48.9％-61.3％.秸秆中养分释放速率表现为K＞P＞N≈C.节水栽培模式下小麦秸秆还田腐解率和养分释放率均显著高于常规栽培.秸秆还田后,土壤微生物数量以及土壤脲酶、碱性磷酸酶和蔗糖酶活性均呈现“前期迅速增加,中期急剧减少,后期缓慢减少”的变化特征,而纤维素酶活性呈现“前期剧升、中期缓增、后期骤降”的变化趋势.小麦秸秆在节水栽培模式下还田土壤微生物数量和酶活性均显著高于常规栽培.适当增加秸秆用量可以提高微生物数量和酶活性,用量过高对细菌和放线菌数量有负效应.秸秆还田可显著提高土壤有机碳和养分含量.土壤有机碳、全氮、碱解氮和速效磷含量在整个试验期间均呈增加趋势.速效钾含量在秸秆还田30 d时达到最高,而后则逐渐降低.节水栽培模式下秸秆还田后土壤有机碳和养分含量的提高效应显著高于常规栽培.提高秸秆用量对土壤养分含量有显著的正效应.