Pedological characterization, classification and evaluation of the potential for maize production of Solomon Mahlangu Campus farm Morogoro, Tanzania
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Date
2016
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Sokoine University of Agriculture
Abstract
In Tanzania, limited attention has been channeled towards the assessment of the fertility status of the soils in areas perceived as suitable for agricultural activities, mainly crop production. In the absence of reliable soil fertility data and information, agricultural land use, and in particular crop production has resulted in very low yields of most of the crops, with subsequent land degradation. The Solomon Mahlangu Campus (SMC) farm – Sokoine University of Agriculture, which is used mostly for crop production, mainly maize and pastures, as well as teaching and research, has not been critically assessed with regard to its soil fertility status, and hence its agricultural potential. This study was carried out with an overall objective of developing the best management packages for the improved maize crop production of Solomon Mahlangu Campus farm. Specifically the study aimed at i) to characterize and classify the soils of the study area using the criteria of the Soil Taxonomy and World Reference Base for Soil Resources soil legend. ii) to establish and evaluate the suitability of soils of the SMC farm for maize production and; iii) to determine the response of maize to different levels of N, P and FYM iv) to identify the limiting factors in different soil units.
The study was conducted in the 300 ha of the uncultivated portion of the Solomon Mahlangu Campus farm, Sokoine University of Agriculture. Grid survey at detailed level (scale, 1:7,500) was carried out to select observation and sampling points. At the beginning of the survey, an initial reconnaissance survey of the study area was conducted, followed by transect walks; auguring and selection of representative transect sampling points. Four mapping units’ were thus delineated and identified in the study area. A total of four representatives profile pits (1.5 m x 1.5 m long x 2 m deep/limiting layer) were excavated, studied, described and sampled. Description of the soils and landforms was done comprehensively following standard procedures as outlined in the FAO (2006) guidelines for soil description. Surface soil samples were collected from the 0-30 cm for general soil fertility evaluation. All soil samples collected were mixed properly, air – dried, grounded, sieved using a 2 mm sieve, bagged and labeled, for general chemical and physical analysis. The samples were analyzed according to laboratory manual for soil analysis by Moberg (2000) in the Department of Soil and Geological Sciences at SUA Morogoro. The data of the physical and chemical characteristics of soils were summarized using descriptive statistics. The soils were classified to family level according to Keys to Soil Taxonomy (Soil Survey Staff, 2014) and to WRB soil name- Tier 2 according to the World Reference Base for Soil Resources [IUSS Working Group WRB (2015)]. The land suitability evaluation was done using the FAO Guidelines on land evaluation for rain fed agriculture (FAO, 2006). Screen house studies were also conducted at the Department of Soil and Geological Sciences screen house to determine the effects of different levels of N, P and FYM on the growth response, nutrient uptake and dry matter yields of maize. The experiments were 33 factorial in a completely randomized design (CRD) with three replications. The treatments used consist of three levels of nitrogen (0, 75 and 150 kg N ha-1), three levels of phosphorus (0, 40 and 80 kg P ha-1) and three levels of farmyard manure (0, 5 and 10 t FYM ha-1). Parameters determined included plant height, number of leaves; stem girth, dry matter yields (DMY) and nutrients uptake (N and P). The data collected were analyzed using the analysis of variance (ANOVA) technique and means were separated using the New Duncan’s Multiple Range Test (NDMRT) at 5% level of probability with the Genstat software package 14th edition.
The results of this study revealed that: all the soils belong to the soil order Ultisols and Ustalfs at suborder level in the Soil Taxonomy while Alisols in the Reference Soil Group (RSG) - Tier 1 for the World Reference Base for Soil Resources soil legend. At great group and subgroup levels, P1 was classified as Rhodustults and Typic Rhodustults, P1 and P2 as Haplustults and Typic Haplustults, whereas, P4 was classified as Haplustults and Arenic Haplustults (Soil Taxonomy), which correspond to Haplic RhodicAlisols, HaplicAlisols, Haplic Chromic and HaplicAlisols (World Reference Base) in the Tier 2 for RSG soil name for P1, P2, P3 and P4, respectively. Results obtained also indicated that soils were sandy loam to silt loam in texture with a slightly acidic to mildly alkaline soil reaction (pHwater = 5.96 - 7.27). The mean values for organic carbon (0.29%), total nitrogen (0.04%), available phosphorus (9.0 mg kg-1), cation exchange capacity (9.84 cmol.kg-1), base saturation (21.2%) and exchangeable bases (Ca=0.7, Mg=0.85, K=0.31 and Na=0.21 cmol.kg-1) were low in all the mapping units.. The mean EC value (0.03 ds/m) was low indicating that the soils were naturally non-saline. The evaluation of the soils revealed that all the soils of the four mapping units are currently moderately suitable (S2) for maize production. The major limitations in the study area are low soil fertility status and soil moisture content. The results for the screen house studies show that application of different rates of N, P and FYM had significant influence (P < 0.05) on the growth, nutrients uptake and dry matter yields of maize.
To improve soil productivity and sustain production of the test crop in the area under investigation, the following recommendations were made: i) an integrated nutrient management system should be adopted which embraces a holistic approach of integrated use and management of organic and inorganic nutrient sources in a sustainable way. ii) Periodic soil tests are very imperative to properly monitor the soil fertility indices and prevent soil fertility decline and degradation. iii) The low TN & OC contents in the soils needs to be amended through an integrated nutrients management (INM) iv) Thus, for enhanced performance of maize in the study area; application of a combination of nitrogen, phosphorus and farm yard manure fertilizers at reduce rates (75 kg N ha-1, 40 kg P ha-1 plus FYM 5 t ha) would be sufficient for maize growth, dry matter yields and nutrients content (N and P) in the test soil.v) Further studies are needed in similar abandoned farms in other agro-ecological zones for sustainable maize production in Tanzania.
Description
A THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN SOIL SCIENCE AND LAND MANAGEMENT OF SOKOINE UNIVERSITY OF AGRICULTURE. MOROGORO, TANZANIA.
Keywords
Solomon Mahlangu Campus, Soil fertility evaluation, Soil characterization, Farm yard manure, Soil physico- chemical properties, Morogoro