Empirical analysis of dry spells during growing season with respect to maize crop in Nigeria
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ORIGINAL PAPER
Empirical analysis of dry spells during growing season with respect to maize crop in Nigeria Nnadozie O. Nnoli 1
&
Ahmed A. Balogun 1 & Jerome A. Omotosho 1 & Samuel O. Agele 2
Received: 31 May 2019 / Accepted: 10 July 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Dry spell analysis during growing season with respect to maize crop is performed in nine stations in Nigeria. The main data used are daily rainfall, temperature, relative humidity, wind speed, and sunshine hours (1971–2013) from the Nigerian Meteorological Agency (NiMet), Lagos. The same data set (excluding rainfall and sunshine hours) from 0.125° ERA INTERIM Reanalysis (1979–2013) and daily 0.25° horizontal resolution 3B42 rainfall from the Tropical Rainfall Measuring Mission (1998–2013) are obtained to serve as useful supplement to NiMet data. The daily reference evapotranspiration (ETo) is computed using the methodology described in the FAO Irrigation and Drainage Publication 56 with the Penman-Monteith equation. Dry spells frequency and average maize crop evapotranspiration (ETc) for the initial, mid-season, and late season stages for 118 day maize crop variety are computed. Critical onset dates, lengths, and trends are determined during the mid-season growth stage. MannKendall tests are performed on the onset dates and lengths to ascertain statistically significant trends. In the 9 stations, more (less) critical dry spells occurrence of lengths 5–10 and 11–15 days during the mid-season and 5–10 days only during initial stages leading to less (more) maize yield are generally associated with El-Nino (La-Nina) years. The percentage frequency of midseason spell lengths of category 5–10 days ranges from 4 to 31% for the nine stations. The number of days maize farmers in all the stations could expect first and second critical dry spell occurrences after planting ranges from 35 to 82 and 50–86 days respectively. This finding will aid strategic planning of agricultural operations for enhanced crop yield. Keywords Nigeria . Growing season . Reference and maize crop evapotranspiration . Dry spells
1 Introduction West African monsoon (which affects Nigeria) has the unique characteristics of high seasonal, monthly, and daily variability in its moisture content and (vertical) depth particularly in the lowest 1 km of the atmosphere (Omotosho 1985). The monsoon rainfall and other rain-bearing systems prevail from around March/April to October/November in southern Nigeria while in the northern part they predominate from around June/July to September/October on the average. These are associated with the inter-tropical discontinuity
* Nnadozie O. Nnoli [email protected]; [email protected] 1
Department of Meteorology and Climate Science, The Federal University of Technology, P.M.B. 704, Akure, Nigeria
2
Department of Crop, Soil and Pest Management, The Federal University of Technology, P.M.B. 704, Akure, Nigeria
(ITD) northward movement from 7° N to 22° N (March– August) and southward movement from 22° N to 7°
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