Non-degraded Soils Research Articles

Impacts of long-term organic manure inputs on cultivated soils with various degradation degrees

With an increasing concern of soil health and sustainable development, organic manure application has been readdressed in recent years. In Northeast China, the agricultural industry is highly developed and organic manure resources are abundant, but soil degradation is serious due to extensive expansion of cultivation. Currently, limited information is available on how soils with various degradation degrees respond to long-term manure fertilization. Given that, a comparative study was conducted based on soil functional assessment of croplands with over 35 years of manure fertilization (maize straw compost, SA; cattle manure, CA) and various degradation degrees (none, light, moderate, and heavy). Soils in these croplands were loess-derived Mollisols and concentrated on a gentle to flat slope. Except for the difference in manure fertilization (SA and CA), similar field managements were adopted for these croplands during the past 35 years. Results showed that the impacts of erosion degradation and manure fertilization on soil physical structure lasted across the whole profile (0 ∼ 120 cm), while their impacts on soil nutrient properties were concentrated in shallow layers (<50 cm). Meanwhile, erosion degradation dominated 17.9% of the variance of soil physical structure, and soil profile depth contributed to 15.9% of soil nutrient variation. According to field validation regarding soil erosion modulus and crop yield, principal component analysis (PCA) with a nonlinear scoring method showed a good performance on the integrated soil functional index (ISI) assessment in this study area. The ISI of these croplands was found to be minimally characterized by BD, SOC, TN, AK, sand content, and CEC (R2 >0.64, p < 0.001). In addition, manure fertilization could significantly improve the ISI and maize yield for degraded soils, but had a slight impact on these two indicators for non-degraded soils. In terms of contribution to ISI improvement, SA (1.79% ∼ 283.73%) generally outperformed CA (4.53% ∼ 212.83%), while the latter was more effective in altering soil structure in deep layers (>70 cm). Generally, the ISI and maize yield were more susceptible to erosion degradation than manure fertilization. The obtained results provide useful information for a better cropland management in Northeast China.

Mycobiota in soil of different degree of degradation in perennial fruit plantations

The number and species composition of micromycetes in different types of soils with different degree of degradation in perennial plantations of Malus Mill., Juglans regia L., Corylus avellana L., Prunus domestica L., Pyrus communis L., Rubus idaeus L., Fragaria vesca L. were analyzed. The research was carried out during 2012–2022 years in enterprises of different types of ownership located at the area of the Lviv, Volyn, Vinnytsia, Drinpropetrovsk, Kharkiv and Kherson Oblasts. The obtained results confirmed the differentiation in the number of micromycetes based on the type of soil and the degree of degradation. The smallest number and species composition of mycobiota were found in slightly and severely degraded soils. In total, among the studied samples of different types of soils, 109 species of micromycetes belonging to 25 genera of two divisions Zygomycota and Ascomycota were differentiated and identified, including 14 species (almost 13%) which are pathogenic or producers of mycotoxins and present biohazard. In most cases these species were found in moderately degraded, ordinary chernozem with a low content of humus and its frequency of occurrence was 29.5–48.5%. Among 13 pathogenic species of micromycetes, in moderately degraded ordinary chernozem with a low content of humus, four species non-typical for garden agnocenoses were detected: (A. flavus Link (frequence of occurence 32.5%), A. parasiticus Speare (34.8%), A. pseudotamari Bennet and Klich (37.3%), Claviceps purpurea (Fr.)Tul. (29.5%)). In slightly degraded sod-podzolic soil, three pathogenic species Botrytis cinerea Pers ex Fr, Paecilomyces lilacinum (Thom) Samson, P. verrucosum Dierckx var. Cyclopium (Westling) Samson, Stolk, Hadlok were identified, and their frequency of occurrence was 35.7–45.2%. In non-degraded soils, 93 species of micromycetes were found, including four pathogens (Botrytis cinerea Pers ex Fr, Paecilomyces lilacinum (Thom) Samson, P. verrucosum Dierckx var. cyclopium (Westling) Samson, Stolk, Hadlok, P. expansum Lk), and their frequency of occurrence was 27.5–40.7%.

Effects of technosols based on organic amendments addition for the recovery of the functionality of degraded quarry soils under semiarid Mediterranean climate: A field study

This study aims to evaluate the effects of technosols made with different organic amendments to restore degraded soils in a semiarid limestone quarry. The effects on soil quality, functionality and organic matter dynamics of the technosols amended with waste of gardening, greenhouse horticultural, stabilized sewage sludge and two mixtures of sludge with both vegetable composts were assessed. Several physical and chemical properties, humus fractions, soil respiration and molecular composition was performed after 6 and 18 months. Un-amended soils, and nearby natural undegraded soils served as reference. Amended technosols increased water retention capacity, electrical conductivity, total organic carbon and nitrogen, respect to not amended and natural soils. Humus fraction composition was not altered over time. Un-amended soils, very poor in organic matter, did not show any pyrolyzable compounds or labile soil organic matter by thermogravimetry. In contrast, the pyrochromatograms of natural soils showed lignocellulosic materials, polypeptides and a noticeable presence of alkylic compounds. In technosols with both types vegetable compost, the organic matter structure was more complex, showing compounds from lignin-derived and long-chain alkyl, polysaccharides, chlorophyll isoprenoids and nitrogen. In sludge technosol, a set of sterols was outstanding. The mixtures showed a molecular fingerprint of materials derived from the decomposition of the organic amendments that formed them. These signs of the contribution of different organic matter forms derived from the amendments were also reported by the series exothermic peaks found in the calorimetry. This short-term study indicates a clear effect of the amendments on the recovery of soil organic matter and presumably of its functionality. After the amendments application, microbial activity and soil respiration rates increased rapidly but ceased 18 months later. The molecular composition of the organic matter of the soils amended with plant compost was very similar to that of natural, non-degraded soils in nearby areas.

Measuring hydrological connectivity inside soils with different texture by fast field cycling nuclear magnetic resonance relaxometry

The locution “hydrological connectivity inside the soil” is generally used to disclose how the spatial patterns inside the soil affect the physical–chemical processes at a molecular level to influence water transfer into the soil, the surface runoff and related sediment transport. Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry has been used to measure both structural and functional connectivity by two indexes indicated as structural (SCI) and functional (FCI) connectivity index. Here, FFC-NMR relaxometry has been applied to analyze three samples: two non-degraded soils, having different grain-size distribution, and a degraded soil sampled in a badland area. Proton Larmor frequencies (νL) ranging in the 0.015–35 MHz interval were used on water suspended samples. The relaxograms (i.e., the distributions of the longitudinal relaxation times, T1) obtained by the FFC-NMR investigations were integrated. The resulting S-shaped curves were handled to obtain the aforementioned FCI and SCI parameters. Results showed that the empirical frequency distribution of the SCI index is related to soil texture and structure, while soils having similar SCI revealed different functional connectivity values. This approach allowed (i) to distinguish SCI values of degraded soils from those of non-degraded ones and (ii) to verify whether the structural connectivity index is related to soil texture and structure. The analysis also showed that the variation coefficient of SCI and FCI, achieved from the measurements done at different νL values, is minimum in the measurement range 0.015–1 MHz. The frequency of 1 MHz can be considered the optimal value to have accurate measured connectivity indexes. For the investigated samples, the obtained relationship between FCI and SCI allowed to conclude that high structural connectivity values correspond to a better functional connectivity. Finally, the hydrological connectivity inside a soil was defined as the sum of the two components representing structural and functional perspective.

Total nitrogen is the main soil property associated with soil fungal community in karst rocky desertification regions in southwest China

Karst rocky desertification (KRD) is a type of land deterioration, resulting in the degraded soil and a delicate ecosystem. Previous studies focused on the influence of KRD on the animals and plants, the impact of KRD on microorganisms, especially soil fungi remains to be discovered. This study reveals the change in the soil fungal community in response to KRD progression in southwest China. Illumina HiSeq was used to survey the soil fungal community. Results showed that the soil fungal community in the severe KRD (SKRD) was noticeably different from that in other KRD areas. Statistical analyses suggested that soil TN was the primary factor associated with the fungal community, followed by pH. Phylum Ascomycota was significantly abundant in non-degraded soils; whereas Basidiomycota predominated in SKRD. The ratio of Ascomycota/Basidiomycota significantly decreased along with KRD progression, which might be used as an indicator of KRD severity. Phylum Basidiomycota was sensitive to changes in all the soil properties but AP. Genus Sebacina might have the potential to promote vegetation and land restoration in KRD areas. This study fills a gap of knowledge on changes in soil fungal communities in accordance with KRD progression.

Changes in soil carbon, nitrogen, and phosphorus contents, storages, and stoichiometry during land degradation in jasmine croplands in subtropical China

AbstractSoil degradation is characterized by loss of soil organic matter, decline in fertility, imbalance in elemental content, deterioration of soil structure, and overall a deterioration of soil environment. According to the classification method of Pieri et al. (1992), the soil is classified into different degradation classes by calculating the soil structural stability index (St) of each sample point. We aimed to investigate changes in the contents, storages and stoichiometry of soil carbon (C), nitrogen (N), and phosphorus (P) together with changes in soil physical traits along a soil degradation gradient in jasmine croplands in Fuzhou area (China). The content and storage of soil C and N decreased with increasing intensity of land degradation. Soil organic C content was 15.4%, 32.3%, and 38.8% lower, respectively, in the low, medium, and high degree of degradation soils, than in the nondegraded soils. The soil C:N ratio was 18.5% higher in soils in the middle degree of degradation than in the nondegraded soils. Compared with nondegraded soils, the bulk density of the degraded soils increased and water content decreased. The decrease of soil pH coupled with salinity (conductivity) and the loss of aggregate stability are the main traits that distinguish degraded from nondegraded soils. We also detected a general N and P deficiency that is aggravated by the degradation process. Unreasonable management easily leads to degradation associated with a loss of organic C and total soil nutrients, thus impairing even more a general N and P deficiency in this area. Therefore, higher inputs of organic fertilizer should be added to alleviate the lack of organic matter, and appropriate burial should be conducted to reduce nutrient loss. Moreover, a rise of N and P fertilizer application is also advisable.

Analysis of Degraded and Non-Degraded Soils in Irepodun Local Government Area of Kwara State, Nigeria

Analysis of Degraded and Non-Degraded Soils in Irepodun Local Government Area of Kwara State, Nigeria

Response of common bean (Phaseolus vulgaris L.) to nitrogen, phosphorus and rhizobia inoculation across variable soils in Zimbabwe

Common bean is an important crop with potential to curb malnutrition in poor Sub-Saharan African populations. Yields of common bean (Phaseolus vulgaris L.) are, however poor, limited by low soil phosphorus (P), nitrogen (N) and poor biological N2-fixation. On-farm experiments were carried out to study the effect of N, P and rhizobia inoculation on common bean yield and yield components during the 2014/2015 and 2015/2016 cropping seasons in Eastern Zimbabwe. Experiments were conducted on five farmers’ fields located in two agroecologies; three fields were considered to be degraded with soil organic carbon (SOC) < 4 g kg−1 and available P < 6 mg kg−1, while the two non–degraded sites had SOC > 7 g kg−1 and available P > 15 mg kg−1. Two common bean varieties (Gloria and NUA45) were tested in a split-plot arranged in randomized complete block design. The main plot factor was the combination of N (0 and 40 kg ha−1) and P (0 and 20 kg ha−1), and the sub-plot factors were variety (Gloria and NUA 45) and inoculation with Rhizobium tropici strain CIAT899 (+/− inoculum). At planting, both N and P were applied at 20 kg ha−1, with an additional 20 kg ha−1 N top dressing applied at flowering. Analysis of variance indicated common bean did not respond to rhizobia inoculation (P > 0.05) whilst P significantly increased the number of nodules and active nodules per plant (P < 0.001), and grain yield. Application of 40 kg ha−1 N significantly increased the number of pods per plant, number of seeds per pod, and grain yields. A significant NP interaction was only observed on grain yield for non-degraded soils. Co-application of N and P in non-degraded sites increased grain yields from 0.27 to 1.48 Mg ha−1during the first season and from 0.37 to 2.09 Mg ha−1during the second season. On degraded sites, NP application resulted in uninspiring grain yield gains of 0.09 to 0.19 Mg ha−1 during the first season, and from 0.16 to 0.28 Mg ha−1 in the second season. In general, effects of N or P were not significantly different, suggesting that farmers could invest in either of these nutrients for increased common bean grain yields. Strategically, P investments would be more logical as residual P effects to rotational cereals improve overall cropping system performance. The response of common bean to inoculation in Zimbabwe still needs to be widely investigated for these and other varieties.

Soil pH Is the Primary Factor Correlating With Soil Microbiome in Karst Rocky Desertification Regions in the Wushan County, Chongqing, China.

Karst rocky desertification (KRD) is a process of land degradation, which causes desert-like landscapes, deconstruction of endemic biomass, and declined soil quality. The relationship of KRD progression with above-ground communities (e.g. vegetation and animal) is well-studied. Interaction of soil desertification with underground communities, such as soil microbiome, however, is vastly unknown. This study characterizes change in soil bacterial community in response to KRD progression. Soil bacterial communities were surveyed by deep sequencing of 16S amplicons. Eight soil properties, pH, soil organic matter (SOM), total and available nitrogen (TN and AN), total and available phosphorus (TP and AP), and total and available potassium (TK and AK), were measured to assess soil quality. We find that the overall soil quality decreases along with KRD progressive gradient. Soil bacterial community compositions are distinguishingly different in KRD stages. The richness and diversity in bacterial community do not significantly change with KRD progression although a slight increase in diversity was observed. A slight decrease in richness was seen in SKRD areas. Soil pH primarily correlates with bacterial community composition. We identified a core microbiome for KRD soils consisting of; Acidobacteria, Alpha-Proteobacteria, Planctomycetes, Beta-Proteobacteria, Actinobacteria, Firmicutes, Delta-Proteobacteria, Chloroflexi, Bacteroidetes, Nitrospirae, and Gemmatimonadetes in this study. Phylum Cyanobacteria is significantly abundant in non-degraded soils, suggesting that Cyanobacterial activities might be correlated to soil quality. Our results suggest that Proteobacteria are sensitive to changes in soil properties caused by the KRD progression. Alpha- and beta-Proteobacteria significantly predominated in SKRD compared to NKRD, suggesting that Proteobacteria, along with many others in the core microbiome (Acidobacteria, Actinobacteria, Firmicutes, and Nitrospirae), were active in nutrient limiting degraded soils. This study demonstrates the relationship of soil properties with bacterial community in KRD areas. Our results fill the gap of knowledge on change in soil bacterial community during KRD progression.

National approaches to evaluation of the degree of soil degradation

Approaches to evaluation of the degree of soil degradation and the related normative documents applied by specialists from state institutes for land management of the former Soviet Union in the course of largeand medium-scale soil surveys in the 1960s–1990s are analyzed. It is shown that the types and rates of soil degradation were specified without proper consideration for the taxonomic position of particular soils. Reference (nondegraded) soils were not clearly defined, which made it difficult to judge the degree of soil degradation by means of a comparative analysis of degraded and nondegraded soils. Such reference soils are suggested for several types of soil degradation (dehumification, compaction, depletion of nutrients, etc.). Additional diagnostic criteria of the degree of soil degradation caused by wind and water erosion, waterlogging, swamping, and other adverse processes are specified. The study of qualitative and quantitative changes in the soil properties during the post-Soviet period is important for the development of land monitoring system and for the analysis of economic aspects of land degradation. To ensure reliability of data on changes in the soil properties and soil cover patterns, possible errors related to incorrect comparison of the data obtained by traditional and modern approaches should be taken into account.

Influence of two bacterial isolates from degraded and non-degraded soils and arbuscular mycorrhizae fungi isolated from semi-arid zone on the growth of Trifolium repens under drought conditions: Mechanisms related to bacterial effectiveness

The limited growth and nutrition of plants growing in semi-arid zones may be overcome by the inoculation with selected soil microorganisms [bacteria or arbuscular mycorrhizal fungi (AMF)]. In this article we investigate how autochthonous AM fungi and the two most abundant cultivable bacterial groups, isolated from dried degraded (B1) and non-degraded (B2) soil, affect Trifolium repens growth under water limiting conditions. On the other hand, and with attempt to characterize biochemically both isolates, we also analysed the indole acetic acid (IAA) and proline production as well as the antioxidant response of both isolates subjected to an increasing osmotic stress degree caused by Polyethylene glycol (PEG). When the bacteria were grown in axenic culture at increasing osmotic stress caused by PEG levels (from 0 to 30%) they show different osmotic response. B2 produced the highest IAA and proline amount under the strongest stress condition (30%). Similarly, under 30% PEG, B2 showed 6 times less CAT and two times more APX than B1 while SOD resulted similar in both strains. Bacterial CAT and APX activities were more sensitive than SOD to osmotic stress which is an indication of bacterial response to drought and reflect the diversity and intrinsic osmotic stress tolerance of these both bacteria. AMF or bacterial inoculated plants widely decreased stomatal conductance and increased the relative water content, both values are important for plants growing in soil with water limitation.

Assessing air-drying and rewetting pre-treatment effect on some soil enzyme activities under Mediterranean conditions

Soil enzyme activities are useful indicators of soil quality as they are very sensitive to disturbance. Sample storage or pre-treatments could affect the results in these assays, which are normally determined in fresh samples, kept cold or frozen. The objectives of this study were to (i) evaluate the effect of air-drying or air-drying and rewetting on β-glucosidase, acid phosphatase and urease activities in soils from different locations, degradation status and sampling seasons, and (ii) assess if air-drying or air-drying and rewetting is an accurate sample storage and pre-treatment procedure for enzyme activities in soil quality evaluations under semiarid Mediterranean conditions. Our results showed that urease, phosphatase and β-glucosidase activities were hardly affected by air-drying of degraded and non-degraded soils from the two locations studied in all seasons. Short incubations (4, 8 and 12 d at 23 °C) of rewetted air-dried soil at 55% of water-holding capacity showed different patterns depending on the enzyme studied. Urease and β-glucosidase activities were relatively stable during incubation, with several significant ( P<0.05) shifts up and down in some soils and samplings. However, acid phosphatase showed an increase in activity with incubation, of between 5% and 50% relative to air-dried samples. These increases followed no pattern and were unrelated to soil characteristics or sampling date. Hence, urease, phosphatase and β-glucosidase activities determined in air-dried soil samples seem to be representative of those obtained under field-moist conditions. In contrast, short incubations of rewetted soil samples can produce fluctuations in these enzyme activities, mainly of acid phosphatase, and estimations in these conditions are not so representative of field-moist soil values.

Carbon Stocks in Pampean Soils: A Simple Regression Model for Estimation of Carbon Storage Under Nondegraded Scenarios

Using published data from a soil survey, a carbon (C) inventory of Pampean soils was performed. As a mean, carbon storage in the 0–20 cm soil layer is 40 t C/ha for the region, decreasing to about half in the 20–50 cm depth. In the 0–50 cm stratum stored, carbon is 3.3 109 t corresponding to a surveyed area of 57 Mha. By multiple‐regression analysis, an explanatory model of carbon content at different depths could be adjusted that accounts for 92% of variability of carbon levels in nondegraded soils. Climate, texture, and depth were the independent variables included in the model. When comparing carbon stored in the 0–20 cm layer of degraded soils belonging to the Rolling Pampa, an area subjected to cultivation since the nineteenth century, predicted carbon by the model averaged 60 t C/ha, and observed carbon content rounded 40 t C/ha. So this area lost around one‐third of the stored carbon in the upper soil layer by cropping. A similar estimation of carbon losses may be performed by other methodologies. Regression appeared to be a suitable tool for predicting soil degradation and carbon sequestration potential.

Nitrogen use efficiency by maize as affected by a mucuna short fallow and P application in the coastal savanna of West Africa

Maize is the primary food crop grown by farmers in the coastal savanna region of Togo and Benin on degraded (rhodic ferralsols), low in soil K-supplying capacity, and non-degraded (plinthic acrisols) soils. Agronomic trials were conducted during 1999–2002 in southern Togo on both soil types to investigate the impact of N and P fertilization and the introduction of a mucuna short fallow (MSF) on yield, indigenous N supply of the soil, N recovery fraction and internal efficiency of maize. In all plots, an annual basal dose of 100 kg K ha−1 was applied to the maize crop. Maize and mucuna crop residues were incorporated into the soil during land preparation. Treatment yields were primarily below 80% of CERES-MAIZE simulated weather-defined maize yield potentials, indicating that nutrients were more limiting than weather conditions. On degraded soil (DS), maize yields increased from 0.4 t ha−1 to 2.8 t ha−1 from 1999 to 2001, without N or P application, in the absence of MSF, with annual K application and incorporation of maize crop residues. Application of N and P mineral fertilizer resulted in yield gains of 1–1.5 t ha−1. With MSF, additional yield gains of between 0.5 and 1.0 t ha−1 were obtained at low N application rates. N supply of the soil increased from 10 to 42 kg ha−1 from 1999 to 2001 and to 58 kg N ha−1 with MSF. Application of P resulted in significant improvements in N recovery fraction, and greatest gains were obtained with MSF and P application. MSF did not significantly affect internal N efficiency, which averaged 45 kg grain (kg N uptake)−1. On non-degraded soils (NDS) and without N or P application, in the absence of MSF, maize yields were about 3 t ha−1 from 1999 to 2001, with N supply of the soil ranging from 55 to 110 kg N ha−1. Application of 40 kg P ha−1 alone resulted in significant maize yield gains of between 1.0 (1999) and 1.5 (2001) t ha−1. Inclusion of MSF did not significantly improve maize yields and even reduced N recovery fraction as determined in the third cropping year (2001). Results illustrate the importance of site-specific integrated soil fertility management recommendations for the southern regions of Togo and Benin that consider indigenous soil nutrient-supplying capacity and yield potential. On DS, the main nutrients limiting maize growth were N and probably K. On NDS, nutrients limiting growth were mainly N and P. Even on DS rapid gains in productivity can be obtained, with MSF serving as a means to allow farmers with limited financial means to restore the fertility of such soils. MSF cannot be recommended on relatively fertile NDS.

Economic impacts on cotton production due to land degradation in the Gediz Delta, Turkey

Soil salinity and waterlogging and other forms of land degradation reduce the agricultural productivity and farm income , while threatening the sustainability of agriculture in many areas. The purpose of the study is to estimate the economic impacts of land degradation on cotton production in the Gediz Delta, Turkey, where salinization and waterlogging threaten the sustainability of irrigated agriculture. Salinity and waterlogging have developed over time in the region, due to unfavorable use of irrigation water and inadequate drainage. We use data collected in a survey of farmers in the region to estimate regression models for cotton production on degraded and non-degraded soils. We conclude that cotton yields are reduced by 34.4% and gross margins are reduced by $860.2/ha, as a result of land degradation.

Performance of Pepper (&lt;i&gt;Capsicum Fructescens&lt;/i&gt; L.) on simulated degraded and non-degraded soils as affected by mycorrhiza inoculation and organomineral fertilizer

Performance of Pepper (&lt;i&gt;Capsicum Fructescens&lt;/i&gt; L.) on simulated degraded and non-degraded soils as affected by mycorrhiza inoculation and organomineral fertilizer

Explaining yield gaps on farmer-identified degraded and non-degraded soils in a Sahelian irrigated rice scheme

Farmers in the Foum Gleita irrigation scheme in southern central Mauritania experienced declining rice yields, and within a decade after its establishment 12% of the scheme's land had been abandoned. Actual rice yields (≤4.0 t ha −1) are low in comparison with potential yield (ca. 8 t ha −1) and with yields elsewhere in the Sahel (4–6 t ha −1). Farmers related the productivity problems to salt efflorescences on the soil surface. Rice yields on the ‘upper and middle slope’ soils were lower (3.4 t ha −1) than the yields on soils further down the slope (> 4.2 t ha −1). Farmers classified the ‘upper and middle slope’ soils as degraded, but following the USDA classification the soils could not be classified saline or sodic. Low yields on the ‘degraded’ soils were related to co-limitation of nitrogen (N) and phosphorus (P), which was due to low soil N supply (ca. 18 kg ha −1), low soil P supply (ca. 8 kg ha −1), occasional low N fertilizer doses (35 kg N ha −1) in combination with low N fertilizer recovery efficiency (0.3 kg kg −1), or non-application of P fertilizer. On the ‘non-degraded’ soils, soil P supply (ca. 16 kg ha −1) was higher and N deficiency prevailed despite a higher soil N supply (ca. 32 kg ha −1) and a higher N fertilizer recovery efficiency (0.4 kg kg −1). Higher contents of carbonate salts in the ‘degraded’ soils increase soil pH (> 7.5) and are, therefore, likely to contribute to low soil P supply and low N fertilizer recovery efficiency.

Sustainable land use in the Sudano-Sahelian zone of Mali: exploring economically viable options using multiple goal linear programming

Technical options in crop and animal husbandry to reduce soil nutrient mining and other forms of natural resource degradation in the Sudano-Sahelian zone should be economically attractive, if they are to be adopted. A model is presented in which agronomic and economic information and goals are combined to explore possibilities for agro-ecologically sustainable and economically viable land use in three different climatic regions in Mali and for a situation of non-degraded soils. The time frame of the study is to the year 2010. For each region, an agro-ecologically sustainable land use system (a combination of crop, livestock and pasture production systems) that maximizes income of the agricultural sector and satisfies self sufficiency targets is identified. Special attention is given to the use of chemical fertilizer in crop activities. It is shown that use of chemical fertilizer is an important element of sustainable and economically viable land use, especially in higher rainfall regions. Population size has a marked effect on optimal land use systems in the regions, but self sufficiency is not endangered even if the population is 50% higher than estimated for 2010. It is argued that results should not be used to simulate the actual situation or future developments, but to define priorities for agricultural development in the Sudano-Sahelian region.

Seed mass and light requirements for regeneration in Southeast Asian rain forest

Seed mass values are given for 140 species of primary lowland rain forest and associated secondary forests in Singapore. Among shade-tolerant species of primary forest there is a trend for a decrease in mean seed mass with tall trees &gt; woody climbers &gt; small trees &gt; shrubs &gt; herbs; the differences between tall trees and small trees or shrubs or herbs, and between herbs and small trees or woody climbers are significant. There are a few light-demanding herbs or shrubs in the primary forest; among small trees, light demanders have significantly lower seed mass values than shade tolerators. In 9 out of 13 comparisons within taxa including both shade tolerants and light demanders the former had appreciably larger seeds than the latter. Two out of 13 comparisons involved very small seeded shade tolerators, and one a notably large-seed light demander. Many shade-tolerant herbs, shrubs, and trees have seed mass values much smaller than those of trees of secondary forest conventionally regarded as small seeded, and exploit moist, litter-free sites, e.g., steep microslopes. The trees of secondary forests on degraded soils do not differ significantly in seed mass from those on nondegraded soils. Key words: seed mass, light requirement, regeneration, tropical rain forest, phylogenetic analysis.

Early Secondary Succession in an Elfin Woodland in the Luquillo Mountains of Puerto Rico

Regeneration of vegetation during the first six years on three clearcut sites and one plane-wreck site which had suffered breakage and burning in an elfin woodland was by mainly woody sprouts, ferns, and graminoids. The abundance of the latter two and the scarcity of seedlings are atypical of tropical successions on non-degraded soils at lower elevations. Ferns may be favored by the abundance of moisture and graminoids by low competition, while the scarcity of seedlings may reflect inefficient dispersal, wash-out by torrential rains, or low selective pressure for colonizing ability in an infrequently disturbed vegetation type. All aspects of regeneration were slow, suggesting a high-stress environment. A major cause of stress may be low transpiration in a saturated atmosphere, impeding nutrient distribution within plants; temperatures apparently do not become low enough seriously to retard growth, and superficial root systems seemingly adapt plants to the saturated soil. The space needed by these superficial systems may hinder coverage of the ground.