Effects of four organic amendments on some soil physical and chemical properties were investigated in Awka, Anambra State in southeastern Nigeria. Over the years, use of synthetic materials in crop production has been a common practice globally. The attendant detrimental effects of the chemicals used in the formulation of these synthetics on animal and human health as well as the environment has made researchers to look out for a better agronomic practice that would not only improve productivity but at the same time sustain a healthy environment. Sole maize, sole cowpea and maize-cowpea intercrop (study area conventional practices) were planted using four soil organic amendments viz: cassava peel (CP), poultry manure (PM), pig waste (PW) and rice husk (RH) at the rate of 20 t ha–1 with the fifth as the control. The treatments were laid out in a 3 × 5 factorial in randomized complete block design and replicated four times. Data on the treatments’ effects on the selected soil physical properties (bulk density, total porosity, soil moisture) and chemical properties (soil pH, available phosphorus, cation exchange capacity (CEC), organic carbon, exchangeable bases and exchangeable acidity) were subjected to factorial analysis of variance using GenStat 2006 Edition. Results indicated that for sole maize, the amendments had significant effect onexchangeable Al3+and Na+; organic carbon, soil pH, available phosphorus and CEC but had no significant effect on Ca2+, H+, Mg2+ and K+ as compared to the control. For sole cowpea, compared to the plots with no amendment (control), all the chemical parameters analyzed differed significantly except organic carbon. Whereas, for maize-cowpea intercrop the treatments had no significant effect on Al3+, Na+, K+ and available phosphorus but differed significantly in exchangeable H+, Ca2+, Mg2+, organic carbon, soil pH, and CEC. There was a decrease in bulk density following the amendment. For sole maize, sole cowpea and maizecowpea intercrop; bulk density, total porosity and moisture content of the amended plots were significantly (p< 0.05) influenced. Organic amendments also significantly improved the growth and yield of maize and cowpea in both the sole and intercrop systems. Generally, poultry manure resulted in higher plant height,number of leaves and leaf area for maize; vine length, number of branches for cowpea as compared with other amendments. Hence, poultry manure was the most effective organic amendment in improving the soil physical and chemical properties as well as the growth and yield of cowpea and maize. Key words: Growth, maize-cowpea intercrop, soil physical and chemical properties, soil organic amendments
Soil organic carbon (SOC) and total soil nitrogen (TSN) dynamics have both pedological and agronomic basis. Knowledge of their retention within aggregate hierarchies of varying soil textures as influenced by land use change is limited. The capacity of loam (L), clay loam (CL), sandy loam (SL) and sandy clay loam (SCL) soils to retain SOC and TSN in water-stable aggregate (WSA) at 10-cm intervals of 0-30 cm topsoil depths under cultivated and bushfallow/ uncultivated systems was investigated. The soils showed high dispersion ratio and great variations in aggregate silt and clay indices (CL > L > SCL > SL) under both land uses. Across soil depths, the uncultivated CL, SL and SCL soils had moderate to high > 2.00 mm WSA whose reduction due to cultivation impact was more pronounced in SL than in CL soil. Across soil depths and land uses, SOC content seemed higher in the macro- (> 0.50 mm) than in the micro- (< 0.50 mm) aggregates of all the soils while the reverse marked aggregate TSN content in almost all the soils. Cultivation mostly reduced macro-aggregate-associated SOC and TSN in L > CL > SL and in L > SL > CL > SCL soils, respectively. However, cultivation showed no reduction influence on micro-aggregate-associated SOC of all the soils. Cultivation-related reduction in micro-aggregate-associated TSN was more pronounced in the generally more ‘clayey’ CL and SCL than the L and SL soils. So, the potential of bush-fallowing to enhance micro-aggregateassociated TSN storage and stabilization against adverse influence of cultivation depends on soil texture.
Soils on coastal plain sands of southeastern Nigeria have hitherto been referred to as fragile sandy and acidic soils of low base saturation, cation exchange capacity (CEC) and fertility, as evidenced by the extensive land degradation evident in the region. This underscores the need for the characterization of the soils for sustainable use. Three profile pits were therefore dug on the upper, middle and bottom slopes of three towns in the rainforest belt underlain by the coastal plain sands. The results showed that the topsoil of the soils was generally sandy, with relatively more clayey subsoil. The pH ranged from extremely acidic (< 4.4) to slightly acidic (6.1- 6.5). They had low organic matter, low total nitrogen, low effective CEC, low Al saturation and moderate base saturation. The soils of the upper and the middle slopes were classified as Arenic Kandiudult by the United States Department of Agriculture’s (USDA) Soil Taxonomy or as Chromic Acrisols by the World Reference Base (WRB) for Soil Resources classification system, while that of the bottom slope was classified as a TypicDystrudept (USDA Soil Taxonomy) / Dystric Cambisol (WRB classification system). The upper slope had a USDA land capability class of IIes and a United States Bureau for Reclamation (USBR) land capability class of 2v/C. The middle slope and the bottom slope both had USDA and USBR capability class of IVs and 3v/C, respectively. Though moderately to marginally irrigable, the soils can still produce increased and sustainable agricultural yield if the appropriate land use and husbandry practices are adopted. Key words: Coastal plain sands, land use planning, soil characterization, toposequence, tropical rainforest
This work was carried out in collaboration between all authors. Author JCN designed the study, wrote the protocol and wrote the first draft of the manuscript. Author AOO managed the literature searches;analyses of the study performed the spectroscopy analysis. Author CAI managed the experimental process and author TW identified the species of plant. All authors read and approved the final manuscript.
We investigated the tillage and residual effects of some organic amendments on aggregate -associated soil carbon (C WSA) and yield of maize and cowpea intercrop in an Ultisol, Southeastern Nigeria. A land area of 0.1125 ha was planted to sole cowpea, sole maize and maize-cowpea intercrop using minimum tillage (NT) and conventional tillage (CT) with poultry droppings (PD), pig waste (PW), and Cassava peels (CP) as amendments at the rates of 20, 90, 100 t/ha respectively and a control. The experimental design was a split -split plot in a Randomized Complete Block Design (RCBD) with three replications. The same crops, treatments, and replications were maintained for two experimental years (2011 and 2012), after that the residual effect of the amendments on aggregate-associated soil carbon (C WSA) and yield of the test crops was investigated in 2013. Consecutive application of organic amendments for the two years necessitated great improvement on aggregate-associated soil carbon (C WSA) for aggregate sizes > 0.25mm. However, when the amendments were withdrawn, there was a reduction in C WSA values though still significant except for aggregate sizes 1-0.5mm. Pig waste was observed to perform better than all the other amendments followed by Poultry Droppings in aggregating the soil. Tillage had a significant effect on C WSA for aggregate sizes >0.05mm, CT performed better than NT. Organic amendments significantly influenced cowpea and Maize both as sole and intercrop, however, it was observed that the intercrop had a tremendous improvement at the residual compared to the previous years.
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