Years Of Continuous Cultivation Research Articles

Effects of an efficient straw decomposition system mediated by Stropharia rugosoannulata on soil properties and microbial communities in forestland

Cultivation of Stropharia rugosoannulata with straw in forestland is effective for straw biodegradation and can prevent the waste of straw resources and environmental pollution and generate economic benefits. However, there is a lack of systematic evaluation of spent mushroom substrate (SMS) input into forestland, such as soil properties and microbial succession. In this experiment, 0 (CK), 10 (SA), 20 (SB), 30 (SC), 40 (SD), and 50 (SE) kg/m2 straw were used to cultivate S. rugosoannulata, and two soil layers (0–10 cm, 10–20 cm) of the cultivated forestland were analyzed. The results indicated that SMS significantly promoted nutrient accumulation in forestland. The bacterial alpha diversity in the SC treatment group was greater than that in the control and gradually decreased to the control level with interannual changes, while the trend of fungal alpha diversity was opposite to that of bacterial alpha diversity. Furthermore, the SC treatment group positively affected soil nitrogen metabolism-related microorganisms for two consecutive years and significantly promoted tree growth. Habitat niche breadth and null model analysis revealed that bacterial communities were more sensitive than fungal communities after SMS input. Linear mixed model (LMM) analysis revealed that SMS supplementation significantly positively affected bacteria (Gammaproteobacteria and Bacteroidota) and significantly negatively affected fungi (Coniochaetales). The constructed fungal-bacterial co-occurrence networks exhibited modularity, and the five types of bacteria were significantly correlated with soil organic matter (SOM), soil organic carbon (SOC), available potassium (AK), available phosphorus (AAP) and available nitrogen (AN) levels. The structural equation model (SEM) showed that bacterial diversity responded more to changes in soil nutrients than did fungal diversity. Overall, 30 kg/m2 of straw decomposition and 2 years of continuous cultivation were beneficial to soil health. This study provides new insights into the rational decomposition of straw and maintenance of forestland ecological balance by S. rugosoannulata.

Distribution of Soil Chemical Properties of Smallholder Farms on Derelict Mined-Sites of Jos South LGA, Jos Plateau, Nigeria

Tin mining environments have constituted a degrading challenge to smallholder farmers whose lands have been overtaken. Attempts by smallholder farmers to restore the lands to farming are faced with soil productivity constraints. Yet, these farmers struggle to cultivate farms in-between the mined lands to meet up with subsistence food requirements. To date, the farmers have identified areas with low and high potentials due to years of continuous cultivation. This study was conducted in an environment that had undergone mining on a larger scale and is now undergoing surface mining on a small scale. Thirty-one (31) soil samples were taken at a depth of 0-20cm to investigate the spread of soil chemical properties on smallholder farms. Coordinates of the samples were acquired using GPS to create georeferenced continuous surfaces. The results indicated that the majority of the soil's chemical properties varied moderately. Organic matter (0.89-1.74%) and nitrogen (0.045 - 0.096%) needed mostly by crops were very low due to uninformed distribution of soil chemical properties. Geostatistics was used to generate continuous surfaces through Kriging. The small nugget effect showed spatial continuity between the neighboring points. Strong spatial dependence occurred for all soil nutrients tested, due to intrinsic soil properties such as soil parent material, topography, texture, and mineralogy. Generally, the spread of soil nutrients on the smallholder farm coincides with the smallholder farmers' identified potential areas. The study suggests that for proper nutrient interventions on the farms, distribution of soil nutrients on the farms should be done to avoid excesses and shortages of inorganic and organic interventions.

Insecticide contamination in organic agriculture: Evidence from a long-term farming systems comparisons trial

Synthetic pesticides applied in conventional agriculture to control pests tend to compromise ecosystem services, and their residues may contaminate organic agriculture. To understand the significance of this contamination, also in small-scale farming systems in sub-Saharan Africa, quantitative data is required. Therefore, we compared synthetic insecticide and botanical/biopesticide residues in conventional and organic agricultural production systems after nine years of continuous cultivation of a maize-based crop rotation system at two sites in Kenya. Our results show high detectable concentrations of synthetic insecticide residues (imidacloprid, acetamiprid, chlorpyrifos, and chlorantraniliprole) in conventional plant produce and soil. Furthermore, the organophosphate chlorpyrifos was detected at concentrations above European Union Maximum Residue Limits (MRL) for plant produce, indicating potential risks for human health. Additionally, we detected imidacloprid, acetamiprid, chlorpyrifos, and chlorantraniliprole concentrations in the soil, indicating potential environmental harm. No residues of biopesticide/botanicals were detected in any of the production systems. However, we detected imidacloprid and chlorantraniliprole in organic plots. The findings indicate that the MRLs can be crossed even if synthetic insecticides are applied according to or below the recommended rates on the conventional plots. Thus, synthetic insecticides potentially risk human health and the environment, while botanicals and bio-pesticides represent a safe alternative.

Untargeted metabolomics reveal rhizosphere metabolites mechanisms on continuous ramie cropping.

Ramie is an important fiber feed dual-purpose crop in China and plays an important role in the national economy. However, ramie yield and quality can be reduced after many years of continuous cultivation. Currently, relatively little research has been conducted on rhizosphere metabolites and their pathways in continuous ramie cropping. Therefore, a healthy group (CK) and obstacle groups (XZQG, JZ, DJY, and GXD) with 8 years of continuous cultivation were selected for the study. LC-MS and GC-MS untargeted metabolomics were used to explore and analyze ramie rhizosphere metabolites and pathways. The results revealed that significant differences in the agronomic traits of ramie occurred after 8 years of continuous cultivation, with dwarfed plants and decreased yields in the obstacle groups. Metabolomic analysis identified 49 and 19 rhizosphere metabolites, including lipids, organic acids, phenols, and amino acids. In addition, four differential metabolic pathways (phenylpropanoid biosynthesis, fatty acid metabolism, amino acid metabolism, and ascorbate and aldarate metabolism) were elucidated. It was also clarified that sinapic acid, jasmonic acid, glutamine, and inositol might be the main metabolites affecting ramie continuous-cropping obstacle groups, and they were significantly correlated with ramie agronomic traits and physiological indicators. This provided important insights into the mechanisms affecting continuous ramie cropping. Accordingly, it is expected that the increase or decrease of sinapic acid, jasmonic acid, glutamine, and inositol in the soil will alleviate obstacles to continuous ramie cropping and promote the healthy development of the ramie industry in the future.

Changes in soil fertility and microbial communities following cultivation of native grassland in Horqin Sandy Land, China: a 60-year chronosequence

BackgroundGrassland conversion to cropland is a prevailing change of land use in traditionally nomadic areas, especially in the Mongolian Plateau. We investigated the effects of grassland conversion followed by continuous cultivation on soil properties and microbial community characteristics in Horqin Sandy Land, a typical agro-pastoral transition zone of Northern China. Soil samples were collected from the topsoil (upper 20 cm) across a 60-year cultivation chronosequence (5, 15, 25, 35 and 60 years) and unconverted native grassland. Soil physico-chemical properties were determined and high-throughput sequencing was used to assess microbial community diversity and composition.ResultsGrassland cultivation resulted in changes to soil properties in both the short and longer term. Initially, it significantly increased soil bulk density (BD), electrical conductivity (EC), soil total nitrogen (TN), available phosphorus (AP) and available potassium (AK) concentrations, while reducing soil water content (SWC) and soil organic carbon content (SOC). Over the next 35–55 years of continuous cultivation, the trend for most of these characteristics was of reversion towards values nearer to those of native grassland, except for SOC which remained highly depleted. Cultivation of grassland substantially altered soil microbial communities at phylum level but there was no significant difference in microbial α-diversity between native grassland and any cropland. However, soil bacterial and fungal community structures at phylum level in the croplands of all cultivation years were different from those in the native grasslands. Heatmaps further revealed that bacterial and fungal structures in cropland tended to become more similar to native grassland after 15 and 25 years of cultivation, respectively. Redundancy analysis indicated that SOC, EC and BD were primary determinants of microbial community composition and diversity.ConclusionsThese findings suggest that agricultural cultivation of grassland has considerable effects on soil fertility and microbial characteristics of Horqin Sandy Land. Intensive high-yield forage grass production is proposed as an alternative to avoid further native grassland reclamation, while meeting the grazing development needs in the ethnic minority settlements of eco-fragile regions.

Changes in rhizospheric microbiome structure and soil metabolic function in response to continuous cucumber cultivation.

With the increasing reliance on intensive arable agriculture, analysis of the problems associated with continuous cropping has become a global research focus. Here, high-throughput sequencing and nontargeted metabolomics were used to evaluate the responses of soil microbial community structure and soil metabolic function to continuous cucumber cultivation (from 1 to 18 years of continuous cultivation) in greenhouses. Continuous cucumber cropping resulted in increased soil nutrient concentrations, but decreased concentrations of available nutrients. The abundance of several bacterial genera associated with nutrient cycling, such as Bacillus and Sphingomonas, was reduced by continuous cucumber cultivation. The abundance of several beneficial fungal genera, including pathogen antagonists (e.g. Chaetomium, Mortierella, Aspergillus, and Penicillium), were found to gradually decrease in response to the increased duration of continuous cropping. 3-amino-2-naphthoic acid and L-valine increased initially and then decreased as the cropping continued, which were related to fatty acid metabolism and amino acid biosynthesis. We also confirmed a close association between microbial community structure and soil metabolites. This study linked the changes in microbial community structure and metabolites in the rhizosphere soil and provided new insights into soil-microbial interactions in continuous cucumber culture systems.

Intercropping of wheat alleviates the adverse effects of phenolic acids on faba bean.

After years of continuous cultivation of faba beans (Vicia faba L.), autotoxic substances accumulate in the soil, leading to a high incidence of Fusarium oxysporum (FOF) wilt. Faba bean-wheat intercropping is often used to alleviate these problems. The goal of this research was to explore the role of benzoic acid and cinnamic acid in promoting the occurrence of faba bean Fusarium wilt and the potential mechanism of faba bean-wheat intercropping to control the occurrence of this disease. We established a field experiment and a hydroponic experiment that involved the inoculation of FOF and the exploration of exogenous addition of cinnamic acid and benzoic acid at different concentrations, the effects on the degree of peroxidation, resistance system, and ultrastructure of faba bean roots. In addition, the antioxidative response of faba bean-wheat intercropping against the autotoxicity of benzoic acid and cinnamic acid was examined. In the field experiment, compared with monoculture, faba bean-wheat intercropping effectively controlled the occurrence of Fusarium wilt, significantly reduced the contents of H2O2 and O2 - in faba bean roots, increased the expression and activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), maintained cell stability, and significantly reduced the contents of benzoic acid and cinnamic acid in faba bean rhizosphere. In the pot experiment, it was found that compared with the control, different concentrations of benzoic acid and cinnamic acid (50, 100, and 200 mg·L-1) significantly increased the content of H2O2 and O2 - in faba bean, decreased the activity and gene expression of antioxidant enzymes SOD and CAT, and damaged cell membrane structure. Furthermore, it promoted the occurrence of Fusarium wilt of faba bean. The faba bean-wheat intercropping alleviated the stress. Benzoic acid and cinnamic acid can increase the content of hydrogen peroxide and superoxide anions in faba bean plants, reduce the enzymatic activity and expression of antioxidant enzyme genes, damage the cell membrane structure, and promote the occurrence of faba bean Fusarium wilt. The faba bean-wheat intercropping can effectively alleviate the autotoxicity of benzoic acid and cinnamic acid and reduce the occurrence of faba bean Fusarium wilt.

Study on Microbial Community Structure and Soil Nitrogen Accumulation in Greenhouse Vegetable Fields with Different Planting Years

Soil microbial communities are an important part of the soil ecosystem in greenhouse vegetable fields, where ammonia-oxidising microorganisms play a key role in nitrogen conversion. The health and stability of the ecological environment of greenhouse vegetable fields are affected by the number of years of continuous cultivation. We used real-time PCR amplification and 16S rRNA gene sequencing to analyse the changes in soil microbial community structure and diversity in different planting years (0, 3, 9, and 13). The content of environmental factors increased with the increase of planting year; the NO3−-N content in the 0–20 cm soil layer showed a cumulative trend, peaking to 1290–1390 mg/kg in year 13. The abundance of operational taxonomic units (OTUs) in the microbial community gradually decreased, and the OTUs of 0–20 cm soil layer in year 13 decreased by 52.2% compared to year 0. The Shannon and Simpson indices indicated a substantial decrease in microbial diversity after year 9. The dominant phyla in the soil microbial community mainly included Firmicutes (23.6%), Actinobacteria (23.2%), Proteobacteria (17.6%), Crenarchaeota (83.4%), and Euryarchaeota (2.7%). Nitrosopumilus and Nitrososphaera in the ammonia-oxidising archaeal (AOA) community and Nitrolancea and Nitrospira in the ammonia-oxidising bacterial (AOB) community dominated the ammonia-oxidising microorganisms. With the increase in planting years in greenhouse vegetable fields, the structure of soil microbial community changed significantly, with soil biomass and diversity significantly decreasing in years 9 and 13. Reasonable fertilization and planting year would improve microbial activity and provide a basis for sustainable utilization and high-quality production in greenhouse vegetable fields.

Bioavailability of Micronutrient Cations in Rice as Influenced by Inorganic Nitrogen Dynamics in Soil under Typic Haplustepts

ABSTRACT Crop establishment methods play a vital role in the predominance of nutrient forms. Nitrogen dynamics in the soil can alter micronutrient availability and uptake. Four treatments each replicated thrice, comprising of three methods of rice establishment viz., puddled transplanted rice (PTR), unpuddled transplanted (UPTR), and direct seeded rice (DSR) in different combinations of rotation with conventionally tilled lentil (CTL) and zero till lentil (ZTL) were compared for their effect on inorganic nitrogen in the soil and its consequent effect on the micronutrient availability in soil and their uptake by rice grain. As per the results obtained from the study, the different establishment techniques with associated treatments after 7 years of continuous cultivation did not have any significant effect on general soil properties like pH, electrical conductivity (EC), organic carbon (OC), and cation exchange capacity (CEC). Treatments had a significant effect on soil nitrogen content and uptake and on soil micronutrient status and their uptake by rice as estimated after harvest of the rice crop. UPTR-ZTL crop rotation with crop residue management and biopriming with Azotobacter was found to be the most efficient management practice and performed better than the conventional crop establishment techniques like PTR and CTL systems. Nitrogen content in soil and plant N uptake showed positive correlations with micronutrient uptake by the rice grain. Significant positive correlations were obtained with the uptake of Fe, Mn, and Zn. Nitrogen dynamics (irrespective of crop establishment methods) in soil especially ammoniacal N, had a positive effect on the cationic micronutrient uptake by the crop, but results were not conclusive enough to suggest the role of N forms on uptake and translocation of micronutrient cations.

Changes in plant species diversity as affected by shading conditions and continuous agricultural practices in kiwifruit orchards

The environmental impact of commercial Mediterranean kiwifruit 'Hayward’ orchards was assessed after ten years of continuous cultivation. Species diversity seems to be influenced both by the subcanopy photosynthetically active radiation (PAR) budget, and the usual agricultural practices in conventional orchards. The largest reduction of species diversity (~64%) was observed in kiwifruit orchards with pergola canopy structure followed by that in T-bar canopy structure (~34%) in comparison with new installed kiwifruit orchards. In excessive shading conditions and particularly in well irrigated kiwifruit orchards with the synergistic effect of the above variables, the highest reduction of plant species has occurred. The continuous herbicides application and the soil compaction are strongly correlated with the reduction of taxa, while the long-term agricultural practices, such as inorganic fertilizers and Cu-fungicides application, have a negative impact on plant species diversity in kiwifruit orchards.

No tillage and residue mulching method on bacterial community diversity regulation in a black soil region of Northeastern China.

Soil microorganisms are important components of agricultural ecosystems; they are important in agricultural soil nutrient cycle and are easily affected by soil tillage. The response of soil microbial community to tillage is very complex, and the effect of the no tillage and residue mulching method on soil microbial diversity remains unclear. In 2019, the soil was collected from an experimental field after 10 years of continuous cultivation in the black soil area of the Sanjiang Plain in Northeastern China. In this study, the diversity and composition of the soil bacterial community and their relationship with soil properties were explored via high-throughput sequencing under no tillage with four residue mulching treatments. No tillage with 60% residue mulching (NTR3) significantly increased the alpha diversity of the rhizosphere soil bacteria and changed the composition of the bacterial community—consistent with changes in soil physicochemical properties. Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla in the sample soil. Soil physicochemical properties explained 80.6% of the changes in soil diversity and composition, of which soil organic carbon, soil pH, and soil temperature were the principal contributors. Our results suggest that no tillage and residue mulching is conducive to increasing soil organic carbon and soil nutrient content, which is a beneficial conservation tillage measure for black soil protection in Sanjiang Plain of Northeast China. The no tillage with residue mulching, especially 60% residue mulching, alters soil bacterial community and highlights the importance of soil physicochemical properties in shaping the diversity and composition of the soil bacterial community. Our findings contribute to a broad understanding of the effects of no tillage and residue mulching on bacterial community differences and provide a scientific basis for the optimization of no tillage measures and sustainable utilization of the black soil of the Sanjiang Plain in Northeastern China.

Precrop Effect of Red Clover (Trifolium pratense L.) and Alfalfa (Medicago sativa L.) on the Population Development of the Northern Root-Knot Nematode Meloidogyne hapla Chitwood, 1949 and on Succeeding Crops—A Pot Study

The northern root-knot nematode, Meloidogyne hapla, is a major pest of many crop species. The objective of the study was to determine how M. hapla population dynamics is affected by two precrops, i.e., Trifolium pratense and Medicago sativa, in three crop durations: one, two and three years of continuous cultivation. Moreover, we set ourselves the task of evaluating the effect of the legume precrop soil on the growth of the succeeding tomato plant (Solanum lycopersicum) and on the nematode population. The experiment was performed outdoors in pots with naturally infected soil. Both precrop species investigated were found to modify the J2 nematode population density in the soil. The galls and nematode females with egg masses were observed on the roots of both studied plant species at the end of each growing season. They appeared to be more abundant on the red clover roots than on those of the alfalfa. The obtained data indicate that the spring soil sampling is more appropriate for the estimation of the M. hapla population density in the red clover precrop soil. The legume precrop soil had a limiting effect on tomato growth and fruit yield. The nematode population negatively influenced tomato growth. The experiment revealed that tomato plants could be planted in alfalfa precrop soil following at least three years of continuous alfalfa cultivation. The same cannot be said of the cultivation of red clover as a precrop for tomatoes.

Characterization of rhizosphere microbial communities in continuous cropping maca (Lepidium meyenii) red soil, Yunnan, China

ABSTRACTContinuous cropping maca systems are widespread in Yunan Province, China. However, the relationships between continuous cropping maca systems and microbes are not well understood. The objective of this study was to determine the effects of continuous cropping maca systems (Maca with 0, 1, 2, and 3 years of continuous cultivation) on the soil microbial community. The results showed that the soil organic matter, total N, total P, and total K contents, as well as maca fresh and dry weight, decreased significantly with increased continuous cropping years. Interestingly, qPCR analysis showed that the bacterial and fungal abundance (DNA levels) decreased and active bacterial and fungal abundance (RNA levels) increased with cropping years from the first to the third cropping (p < 0.05). Moreover, the abundance of actinomycetes in the CK soil was significantly higher than that in the other maca soils. In addition, the continuous cropping system resulted in rich diversity in the fungal structure and had little effects on the bacterial and actinomycete communities. Acidobacteria (50%) and Ascomycota (58.3%) were detected in the continuous cropping maca soils. Based on the present results, continuous cropping of maca not exceeding two years could be optimal to maintain soil nutrition and microbial community.

Effect of nutrient management on soil organic carbon sequestration, fertility, and productivity under rice-wheat cropping system in semi-reclaimed sodic soils of North India.

The ever shrinking agricultural land availability and the swelling demand of food for the growing population fetch our attention towards utilizing partially reclaimed sodic soils for cultivation. In the present investigation, we compared six treatments, like control (T1), existing farmers' practice (T2), balanced inorganic fertilization (T3) and combined application of green gram (Vigna radiate) with inorganic NPK (T4), green manure (Sesbania aculeate) with inorganic NPK (T5), and farmyard manure with inorganic NPK (T6), to study the influence of nutrient management on soil organic carbon sequestration and soil fertility under long-term rice-wheat cropping system along with its productivity in gypsum-amended partially reclaimed sodic soils of semi-arid sub-tropical Indian climate. On an average, combined application of organics along with fertilizer NPK (T4, T5, and T6) decreased soil pH, ESP, and BD by 3.5, 13.0, and 6.7% than FP (T2) and 3.7, 12.5, and 6.7%, than balanced inorganic fertilizer application (T3), respectively, in surface (0-20cm). These treatments (T4, T5, and T6) also increased 14.1% N and 19.5% P availability in soil over the usual farmers' practice (FP) with an additional saving of 44.4 and 27.3% fertilizer N and P, respectively. Long-term (6years) incorporation of organics (T4, T5, and T6) sequestered 1.5 and 2.0 times higher soil organic carbon as compared to the balanced inorganic (T3) and FP (T2) treatments, respectively. The allocation of soil organic carbon into active and passive pools determines its relative susceptibility towards oxidation. The lower active to passive ratio (1.63) in FYM-treated plots along with its potentiality of higher soil organic carbon (SOC) sequestration compared to the initial stock proved its acceptability for long-term sustenance under intensive cropping even in partially reclaimed sodic soils. Among all the treatments, T4 yielded the maximum from second year onwards. Moreover, after 6years of continuous cultivation, the observed EWY (2011-2012) was found to be 41.9 and 33.1% higher in T4 as compared to FP (T2) and T3, respectively. Thus, for maintaining higher yield coupled with improved SOC sequestration and nutrient availability, T4 followed by T6 treatments would be the suitable options for long-term intensive rice-wheat system in partially reclaimed sodic soils of northern India.

Changes in Soil Iron Fractions and Availability in the Loess Belt of Northern China After 28 Years of Continuous Cultivation and Fertilization

Iron (Fe) deficiency in calcareous soils of the Loess Plateau of China is a wide spread issue and primarily affects agricultural production due to the relatively higher soil pH and carbonate content. Understanding the relationships between Fe distribution in soil fractions, Fe availability, and their responses to cropping and fertilization could provide essential information for assessing Fe availability in soils and managing soils to improve Fe availability. A long-term field experiment was established in 1984 in a split-plot design using cropping systems as main plots and fertilizer treatments as subplots on a farmland in the Loess Plateau. The cropping systems included fallow, continuous wheat cropping, continuous alfalfa cropping, continuous maize cropping, and a rotation system that included a legume. Various fertilization treatments using chemical and/or manure fertilizers were included in each cropping system. Soil samples were collected from 0–10 and 20–40 cm depths in 2012. Long-term planting of crops significantly increased the concentrations of available Fe in the soils. The largest increase was observed in the continuous alfalfa cropping system. Long-term cropping significantly increased the concentrations of Fe associated with carbonates and organic matter, but decreased the concentration of Fe associated with minerals in the soils. The effect of fertilization on the distribution of Fe in the soil fractions varied with cropping system and soil depth. The fertilization treatment with manure generally increased the concentrations of Fe associated with the soil fractions. Long-term cropping and fertilization in the highland farmland significantly affected the availability of Fe and the distribution of Fe fractions in the soil.

English

Amorphophallus konjac cannot be cultivated on the same field consecutively for extended periods, but can be cultivated on the same grove. The underlying mechanism for this is unknown and may involve the rhizosphere microbial community. Therefore, the different duration and mode for konjac were researched. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) showed that microbial communities varied by cultivation duration and mode. Seven bacterial phyla were detected in the soil and Proteobacteria was the most abundant of these phyla. The microbial metabolic diversity following three years of continuous cultivation (sample QXFH3) was the highest, and this sample may have contained pathogenic and antagonistic microorganisms. There was almost no disease in the soil sample from grove conditions (QXN0), which was readily distinguishable from soils from field conditions (QXF0). Amino acids, carboxylic acids, and miscellaneous carbohydrates were the main carbon sources utilized by microbes in these soils. The microbial diversity index and multivariate analyses revealed that bacterial diversity increased with cultivation duration. &nbsp; Key words: Discontinuous cultivation, metabolic function, microbial composition, Amorphophallus konjac.

Impact of long term nutrient management on soil fertility determinants and performance of rice in terraced land

The impact of long term nutrient management practices on soil fertility determinants and performance of upland rice after thirteen years of continuous cultivation on terraced land were studied in a field experiment conducted on the experimental farm of the School of Agricultural Sciences and Rural Development under rainfed conditions. Twelve treatments involving N, P and K (NPK) fertilizers, FYM, poultry litter, forest litter, Azospirillum and Zn either alone or in combinations were applied for thirteen years and rice crop cultivated continuously. The organic C content, available N, P and K, number of productive tillers, grain and straw yield increased significantly in all the treatments. The highest accumulation of available N, P and K was observed in NPK+ poultry litter, NPK+ FYM and ½N + PK + ½N forest litter treatments, respectively. After thirteen years the rate of build up of available N, P and K in different nutrient management practices ranged from 5.2 to 16.9, 0.33 to 0.80, and 1.96 to 7.03 ha -1 yr -1 , respectively. Addition of FYM and poultry litter with NPK increased 28.7 and 25.9 per cent in grain yield and 50.3 and 49.4 per cent in straw yield, respectively as compared to NPK alone.

Fifteen-year fallow altered the dynamics of soil phosphorus and cationic balance of a savannah Alfisol

This study was designed to evaluate changes in the dynamics of soil phosphorus and cationic balances of a savannah soil subjected to 45 years of continuous cultivation under different fertilizer management and later left fallow for 15 years. It was conducted on the experimental plots at the Institute for Agricultural Research, Ahmadu Bello University, Nigeria. Treatments consisted of nitrogen (N), phosphorus (P), potassium (K), cow dung manure (D) and their combination (DNPK). Results of P fractionation and cationic distribution were compared with previous studies on the same plot 15 years ago. Organic carbon increased from a range of 3–5 g kg−1 in 1997 to 10.9 g kg−1 in 2012. Similarly, the cation exchange capacity (CEC) of the soil increased from 6.40 cmolc kg−1 in 1997 to 16.4 cmolc kg1 in the present study. The degree of saturation of the CEC by Ca2+ was 68–79% and 10–20% for Mg2+, while that of K+ was 1.5–2%. Although there was an uneven trend in depletion and enrichment of the various P pools, however, the fallow period substantially improved the CEC and the plant available P pools of the soil by more than 200% and 6–259%, respectively.

Root and time dependent soil structure formation and its influence on gas transport in the subsoil

The recovery of soil structure following intensive crop production is essential to maintain good fertility and productivity. It is well known that some crops with specific deep rooting characteristics can improve subsoil structure, but few measurements exist on the time to recovery or direct impacts on gas transport on aeration status, thus we hypothesized that root influence on soil structure formation has a significant impact over aeration. This study examined how far three crops and their different root architectures influenced soil structure and aeration by their ability to generate biopores and cracks. Effects of three crops were investigated: (i) shallow roots (Festuca arundinacea, fescue), (ii) taproot-herringbone (Cichorium intybus, chicory) and (iii) taproot-multibranch (Medicago sativa, alfalfa). They were grown in a Haplic Luvisol in a field experiment near Bonn (Germany) during years 2007–2009. Air diffusion, air permeability and air-filled porosity were analyzed as a function of crop type, crop duration (one, two and three years of continuous cultivation) and soil depth. Results of the diffusion measurements were compared with Buckingham's and Penman's estimation functions with respect to continuity and tortuosity indices.At a depth of 75cm, alfalfa showed more macroporosity than chicory and fescue with means of 13.6%, 2.5% and 3.4%, respectively, and at 90cm means of 17.8%, 2.3% and 4.4%, respectively. Measurements showed decreasing gas diffusion with depth under chicory and fescue cultivation, whereas increasing diffusion with depth under alfalfa. At 90cm depth alfalfa significantly improved diffusion with respect to chicory and fescue with means of 0.035, 0.014 and 0.009 respectively. Greater soil structure development under alfalfa was interpreted from higher tortuosity index. Under chicory, higher continuity and lower tortuosity of pores dominated the advective transport. Significant effects were observed after three years of cultivation, which suggests the time needed for structural changes. The structural changes observed are promising to extend these results to other soils with swell/shrink potential.

Evaluating long-term impact of land use on selected soil physical quality indicators

This paper presents findings of comparative evaluation of selected soil physical quality (SPQ) indicators, obtained from fields subjected to: &gt;50 years of cultivation of three perennial pasture grasses (i) Digitaria smutsii (DS), (ii) Brachiaria decumbens (BD), and (iii) Andropogon gayanus (AG); (iv) &gt;50 years of continuous cultivation (CC) of cereals–legumes; and (v) &gt;20 years of natural fallow (NF). The study was aimed at identifying the land-use system having optimal values for SPQ. Fields under CC had the highest bulk density, and the lowest total porosity (PORt) and macroporosity (PORp), field capacity (FC), and available water capacity (AWC). Perennial pasture grasses fields had significantly higher organic carbon, PORt, FC, AWC, and saturated hydraulic conductivity, and, hence, had better SPQ than CC fields and, in some instances, NF fields. The usefulness of ratios FC/PORt = 0.66 and ACt/PORt = 0.34 as additional indicators for assessing soil response to land-use systems was not proven in this study, and therefore, further studies should be conducted on the subject matter. Pasture grasses improved SPQ values relative to continuous cereal–legume cropping and fallow. The SPQ under CC and NF fields might be best improved by applying organic matter.