Effects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China

The effects of selected land management practices （cross-sloping tillage, ridge culture, organic manure, and straw mulch） on soil water conservation in a southwestern mountainous area, China, were studied during November 2002 to November 2004. The experimental field is divided into three parts based on soil layer depths, 0-60 cm （part Ⅰ）, 0-40 cm （part Ⅱ）, and 0- 20 cm （part Ⅲ）, and they all had the same slope azimuth （SE）, slope （10°）, and slope type （linear）. The experimental plots were subjected to the following treatments： cross-sloping tillage （CST）; cross-sloping tillage with organic manure （CST/ OM）; cross-sloping tillage with straw mulch （CST/SM）; contour ridge culture （CRC）; contour ridge culture with organic manure （CRC/OM）; and contour ridge culture with straw mulch （CRC/SM）, to identify the effects of management practices on soil water. Water contents were determined for soil samples collected, using a 2.2 cm diameter manual probe. Soil water was monitored once every five days from Nov. 20, 2002 to Nov. 20, 2004. The results indicated that, in the study stages, an integration of rainfall, evaporative losses, and crop transcription controlled the basic tendencies of profile （mean） soil water, while land management practices, to a certain extent, only modified its amount, distribution, and routing. Moreover, these modifications also mainly focused on the first 20 cm depth of topsoil layer. When each management practice was compared with control treatment, season changes of profile （mean） soil water were pronounced, while interannual changes among them were not significant. More comparisons indicated that, in the study stages, contour ridge culture had better effects than cross-sloping tillage. And under the same tillage, the combination of organic manure could achieve more than straw mulch. These management practices should be recommended considering the effectiveness of soil and water management techniques in the southwestern mountainous area, China.

SOIL AGGREGATE AND ITS RESPONSE TO LAND MANAGEMENT PRACTICES

This paper provides a broad review of the existing study on soil aggregate and its responses to land management practices. Soil aggregate is used for structural unit, which is a group of primary soil particles that cohere to each other more strongly than other surrounding particles. The mechanism of soil particle aggregation may be expressed by a hierarchical model, which is based upon the hypothesis that macroaggregates （〉250μm） are collections of smaller microaggregates （〈250μm） held together with organic binding agents. Primary particles form microaggregates and then macroaggregates. Carbon （C）-rich young plant residues form and stabilize macroaggregates, whereas old organic C is occluded in the microaggregates. The interaction of aggregate dynamics with soil organic carbon （SOC） is complex and embraces a range of spatial and temporal processes within macroaggregates and microaggregates. The nature and properties of aggregates are determined by the quantity and quality of coarse residues and humic compounds and by the degree of their interaction with soil particles. The mechanisms resulting in the binding of primary soil particles into stable aggregates vary with soil parent material, climate, vegetation, and land management practices. Land management practices, including tillage methods, residue management, amendments, and soil fertility management, enhance soil aggregation. However, there is still much uncertainty in the dynamics of organic matter in macroaggregation and microaggregation, and research is still needed to understand further the mechanisms of aggregate formation and its responses to human activities.

Factors that influence the implementation of sustainable land management practices by rural households in Tigrai region, Ethiopia

Background:Sustainable land management is considered as one of the useful approaches to combat the threat of various forms of land degradation in Ethiopia.Despite this,there is scant information regarding households’decision towards the implementation of sustainable land management practices.This paper,therefore,looks into the determinants for the continued use and choice of the sustainable land management practices by smallholder farmers and its productivity effect in three randomly chosen districts in Tigrai region,Ethiopia.The study uses data from household survey and key informant interviews.The paper employs a binary logit to analyze the determinants for the decision of continued use of sustainable land management practices,and a multivariate probit to analyze the simultaneous adoption decision of sustainable land management practices using cross sectional data collected from 230 randomly selected households.The impact of sustainable land management practices was also evaluated using propensity score matching.Results:Farming techniques,wealth status,agro-ecological variations,and plot level characteristics were found to be associated with the implementation decision of sustainable land management practices by rural households.Besides,institutional supports and access to basic infrastructures influenced the overall continued use of sustainable land management practices and the preference of households toward these practices.The study also finds that the value of crop production of sustainable land management users was on average 77–100%higher than that of nonusers.Conclusions:The results of the current study confirm that the implementation of various sustainable land management practices are influenced by farming technologies deployed by rural households,agro-ecological variations,plot characteristics,and institutional supports.The findings also affirm that most of the sustainable land management practices are complementary to one another,and implementing two or more sustainable land management practices on a given plot is highly associated with higher value of crop production.Such complementarity highlights that the productivity effect of a given sustainable land management practice is enhanced by the use of the other ones.

Effect of Land Management on Soil Hydraulic Conductivity in Gidan Kwano, Niger State, Nigeria

Hydraulic conductivity is one of the most important parameters for flow and transport related phenomena in soil and also a criterion for measuring soil ability to transfer water. There is concern arising from the suitability, efficiency and ease of the different measuring methods use under different land management practices. The purpose of this paper is to determine and evaluate soil hydraulic conductivity under different land management practices which include forest land (teak and Melina plantation), grassland and maize cultivated land using the constant head method. The measurement is at different depth of 0 - 15 cm, 15 - 25 cm, 25 - 50 cm, 50 - 75 cm. The limited means of each land use were used to compare the result obtained through statistical means. All tests were carried out using SPSS at a significance level of 0.05. An ANOVA test was conducted to check if each of the land use is significantly different. The soil in forest zone (Teak plantation and Gmalina plantation) had a significantly high bulk density as 1.7533 cm-3 and 1.6967 cm-3 respectively at depth 50 - 75 cm compared to the low bulk density in the grass, maize cultivated land as 1.5000 cm-3 and 1.4833 cm-3 respectively at depth 50 - 75 cm. However, soil hydraulic conductivity was significantly high in the grass site or soil at the surface with 2.8833 cm·h-1. Results obtained from the different land use serve as Knowledge of variability of soil that can assist in defining the best strategies for sustainable soil management through the provision of vital information for estimating soil susceptibility to erosion, hydrological modelling and efficient planning of irrigation projects.

Assessment of soil microbial and enzyme activity in the rhizosphere zone under different land use/cover of a semiarid region, India

Background:Land use/cover and management practices are widely known to influence soil organic matter(SOM)quality and quantity.The present study investigated the effect of different land use,i.e.,forests viz.mixed forest cover(MFC),Prosopis juliflora(Sw.)DC-dominated forest cover(PFC),and cultivated sites viz.agriculture field(AF),vegetable field(VF),respectively,on soil parameter,microbial activity,and enzymes involved in soil nutrient cycle in a semiarid region of India.Results:The results showed a significant reduction(P<0.05)in soil carbon(SC),soil nitrogen(SN)content(~30–80%)and consequently the soil microbial biomass carbon(SMBC)(~70–80%),soil basal respiration(SBR),soil substrate-induced respiration(SSIR),and soil enzyme activities(β-glucosidase,acid phosphatase,and dehydrogenase)under cultivated sites in comparison with forest sites.Pearson’s correlation showed that a positive correlation of SC with SMBC,SBR,SSIR(P<0.01),and enzymatic activities(i.e.,β-glucosidase,dehydrogenase)(P<0.05)may imply the critical role of SC in regulating microbial and enzymatic activity.Also,a positive correlation of soil moisture with urease activity(P<0.01)was found suggesting it as a significant abiotic factor for soil biological functions.Additionally,based on the PCA analysis,we observed the clustering of SMBC/SC ratio and qCO_(2) nearby AF.Conclusion:Our study suggests that soil microbial parameters(SMBC,SBR,SSIR,SMBC/SC,qCO_(2))and enzyme activity are key indicators of soil health and fertility.Land use/cover alters the SOM content and soil microbial functions.The management strategies focusing on the conservation of natural forest and minimizing the land disturbances will be effective in preventing soil carbon flux as CO_(2) and maintaining the SC stock.