Cultivated steeplands in the humid tropics require better soil management systems to meet increasing food demands. The objective of this 4-yr study was to evaluate the following four contour soil management systems for corn (Zea mays L.) production: (i) contour moldboard plowing (CP); (ii) ridge tillage (RT); (iii) natural grass barrier strips plus moldboard plowing (GCP); and (iv) grass strips plus ridge tillage (GRT). Eight successive corn crops were grown in limed and fertilized soil from 1992 through 1995. On a total land area basis (cropped area plus the area occupied by the grass strips), the 1995 mean grain yields for RT (10.8 Mg ha1) and GRT (10.3 Mg ha1) were significantly greater than yields for CP (10.0 Mg ha1) and GCP (9.6 Mg ha1). The corn grain yields for the CP and RT systems before 1995 ranged from 1.3 Mg ha1 in 1992 to 8.4 Mg ha1 in 1993, while comparable GCP and GRT yields ranged from 1.4 to 7.6 Mg ha1 Excluding the area occupied by the grass strips, the GRT system had the highest 4-yr average corn yield (7.3 Mg ha1) followed by the GCP (7.2 Mg ha1), RT (6.9 Mg ha1) and CP (6.7 Mg ha1) systems. Yields improved during the 1994 and 1995 growing seasons when the grass was not permitted to grow as tall. The combination of contour ridge tillage and contour grass strips has potential for sustaining crop productivity on highly erodible steepland soils in the humid tropics.
Tag: oxisols
Grain crop response to contour hedgerow systems on sloping Oxisols
Farming systems that minimize the rate of soil degradation and optimize food crop yields are needed to sustain soil productivity on sloping, acid, infertile soils in the humid tropics. Research was conducted on two Oxisols with slopes ranging from 22 to 30% to evaluate the performance of several contour hedgerow systems, with and without the addition of 60 kg N ha1 per crop, on rice (Oryza sativa) and maize (Zea mays L.) production. Contour hedgerows were double rows of the tree legume Gliricidia sepium (G); Gliricidia and the native grass Paspalum conjugatum (GPas); Gliricidia and an exotic fodder grass Penisetum purpureum (GPen); double rows of Penisetum (Pen); and a conventional open field (C) farming system without hedgerows. Gliricidia prunings and all crop residues were applied to the soil surface in the alleys, but Penisetum was harvested. Food crop yields in all hedgerow treatments tended to be less than the Control for the first two years, presumably due to the displacement of land planted to the food crop. In the third and the fourth years, the rice and maize yields of Treatments G and GPas exceeded the Control, most consistently when N was not applied. Penisetum reduced food crop yields regardless of N application presumably due to nutrient removal in the fodder. The results indicate that Gliricidia in a contour hedgerow increases food crop yield on strongly acid Oxisols by recycling nutrients and partially supplementing the N demand by the food crops
Comparing Uganda’s indigenous soil classification system with World Reference Base and USDA Soil Taxonomy to predict soil productivity
This study examines three soil classification systems – Buganda, World Reference Base, and US Soil Taxonomy – in order to evaluate their relative strengths and feasibility for making linkages between them. Nine field sites and 16 pedons were considered across the soil landscapes of the Buganda catena. Each identified field pedon diagnostic horizons and characteristics were described and their soils analyzed using standard pedological techniques and measurements. To document the indigenous use of the Buganda classification system, interviews and discussions were held with farmer groups and local extension specialists. Using this local expertise, five local soil units were identified. We also identified two landscape toposequences with pedons that classified into six WRB Reference Soil Groups and five US Soil Taxonomic Suborders. While four local soil classes each mismatched with international systems’ groups, Liddugavu (black) soil corresponded to Phaeozem (WRB) and Udolls (US Soil Taxonomy) and is consistently viewed as the most productive soil due to faster weed growth, diversity of crops it supports and its stable landscape location. Statistical comparisons indicated that the Buganda classes were more homogeneous and effective at separating variability of different soil properties than those of either the WRB Reference Soil Groups or US Soil Taxonomy Suborders. Integrating soil texture, pH and bases information in indigenous system methods could locally complement international classifications and linking the best of both systems would be ideal for the generation of a hybrid system. Our findings show that using the toposequence framework assists in comparing these systems in a way that is useful for scientists and local farmers.