Weather variability in derived savannah and rainforest agroecologies in Nigeria: Implications for crop yields and food security

Weather variability and its effects on agricultural and food systems are burgeoning global concerns. This study examined the effects of weather variability in the derived savannah and rainforest agroecologies, on crop yields in Southwest Nigeria, and what it portends for food and nutrition security in the region. The trends in the distribution of rainfall and temperature were analysed using the Sens method. The effects of weather variability on crop yield and inferences on what it portends for food security were determined using a stepwise regression model. The results revealed that rainfall fluctuations decreased the yields of cassava ( Manihot esculenta ) and yam (Dioscorea spp.) in the derived savannah; while a decrease in temperature may support improved yields for maize ( Zea mays ), sorghum ( Sorghum bicolor ) and cowpea ( Vigna unguiculata ). The increase in yields of cocoa ( Theobroma cacao ) and cocoyam ( Colocasia esculenta ) would be hampered by increasing maximum temperatures in the rainforest agroecology. Increasing rainfall and temperature would impact warmer conditions that support rapid crop putrefaction, flooding, droughts, challenging postharvest crop management, pest and disease proliferation, and ultimately, reduced crop yields. On the other hand, perpetually low rainfall and temperature conditions will cause poor seedling emergence and growth, seed and total crop loss. It is, therefore, imperative that effective climate adaptation and mitigation mechanisms be put in place across the agroecologies in the region.La variabilit\ue9 m\ue9t\ue9orologique et ses effets sur les syst\ue8mes agricoles et alimentaires sont des pr\ue9occupations mondiales en plein essor. Cette \ue9tude a examin\ue9 les effets de la variabilit\ue9 m\ue9t\ue9orologique dans les agro\ue9cologies d\ue9riv\ue9es de la savane et de la for\ueat tropicale humide sur les rendements des cultures dans le sud-ouest du Nigeria, et ce qu\u2019elle pr\ue9sage pour la s\ue9curit\ue9 alimentaire et nutritionnelle dans la r\ue9gion. La tendance de la distribution des pr\ue9cipitations et de la temp\ue9rature a \ue9t\ue9 analys\ue9e \ue0 l\u2019aide de la m\ue9thode Sens. Les effets de la variabilit\ue9 m\ue9t\ue9orologique sur le rendement des cultures et les d\ue9ductions sur ce qu\u2019elle pr\ue9sage pour la s\ue9curit\ue9 alimentaire ont \ue9t\ue9 d\ue9termin\ue9s \ue0 l\u2019aide d\u2019un mod\ue8le de r\ue9gression progressive. Les r\ue9sultats ont r\ue9v\ue9l\ue9 que les fluctuations des pr\ue9cipitations diminuaient les rendements du manioc ( Manihot esculenta ) et de l\u2019igname (Dioscorea spp.) dans la savane d\ue9riv\ue9e ; tandis qu\u2019une diminution de la temp\ue9rature pourrait favoriser l\u2019am\ue9lioration des rendements du ma\uefs ( Zea mays ), du sorgho ( Sorghum bicolor ) et du ni\ue9b\ue9 ( Vigna unguiculata ). L\u2019augmentation des rendements du cacao ( Theobroma cacao ) et du cocoyam ( Colocasia esculenta ) serait entrav\ue9e par l\u2019augmentation des temp\ue9ratures maximales dans l\u2019agro\ue9cologie de la for\ueat tropicale. L\u2019augmentation des pr\ue9cipitations et de la temp\ue9rature aurait un impact sur des conditions plus chaudes qui favorisent la putr\ue9faction rapide des cultures, les inondations, les s\ue9cheresses, la gestion des cultures post-r\ue9colte difficile, la prolif\ue9ration des ravageurs et des maladies et, en fin de compte, la r\ue9duction des rendements des cultures. D\u2019autre part, les pr\ue9cipitations et les conditions de temp\ue9rature perp\ue9tuellement basses entra\ueeneront une mauvaise \ue9mergence et croissance des semis, des semis et une perte totale de r\ue9colte. Il est donc imp\ue9ratif que des m\ue9canismes efficaces d\u2019adaptation et d\u2019att\ue9nuation du climat soient mis en place dans les agro\ue9cologies de la r\ue9gion

Soil physical and hydraulic properties modification under Arachis cultivation in the derived savanna agroecological zone of southwestern Nigeria

Conservation of soil moisture is one of the major limiting factors to crop production. Improvement of soil physical properties could enhance soil moisture conservation, improve crop productivity and reduce food insecurity in sub Saharan Africa. A field study was carried out to determine the effects of 3 plant densities (33333, 66667 and 83333 plants/ha)on soil properties and water loss through evaporation from soils under 2 cultivars of Arachis hypogaeaL. (SAMNUT 10 and SAMNUT 21) and Arachis pintoi(PINTOI) in Ibadan, south western Nigeria. The experiment was a split plot in randomized complete block design with Arachis varieties as the main plot and plant densitiesas subplot with three replications. Data were collected on daily soil water evaporation, bulk density, saturated hydraulic conductivity, particle size, total porosity and permeability. The Soil was loamy-sand and marked reductions in soil water evaporation were observed in surfaces under Arachis varieties compared to bare soil. Reductions in soil water evaporation were 44.5%, 41.1% and 34.7% under SAMNUT 21, PINTOI and SAMNUT 10 respectively. Significant (p= 0.05) improvement on soil structure and hydraulic conductivity was observed under Arachis varieties. Plant density of 66667 plants/ha showed the best positive effect on the improvement of soil physical structures. The cultivation of SAMNUT 21at 66667 plants/ha and PINTOI at 83333 plants/haalong with other measures of sustainable soil water conservation are recommended.Key words: Arachis species, Plant densities, Evaporation,Soil hydrological properties, Food insecurity

EFFECT OF SOIL MANAGEMENT PRACTICES ON EVAPORANSPIRATION OF SORGHUM PLOT

The trial was conducted to quantify soil water loss under sorghum at Samaru (11o 11’N, 7o 36’E, 686m above mean sea level) on the Northern Guinea Savanna Ecological Zone of Nigeria during 2005/06 rainy seasons. The treatments, which consisted of two soil management practices, mulched soil and bared soil, were replicated four times in a randomized complete block design. Microlysimeters were installed at 8 weeks after sowing (WAS) for daily reading of potential evapotranspiration . Data were analyzed using the two way analysis of variance, and Pearson correlation analysis. Results from the two seasons indicated that there was a significant positive correlation between the yield, yield components and potential evapotranspiration under mulched soil. Under bare soil, water loss was not significantly correlated with the yield and yield components

Seasonal water use and water productivity of millet-based cropping systems in the Nigerian Sudan savanna near Kano

Quantification of resource use in dominant millet–cowpea (M–C) and millet–sorghum–cowpea (M–S–C) intercropping systems in peasant agriculture was carried out using farmers' practices, under the low rainfall and poor nutrient supply situations of the semi-arid zone of Nigeria. On-station trials were conducted at Minjibir near Kano during the 1994 and 1995 rainy seasons to determine the components of the water balance and compare water use (WU) and water productivity of millet planted sole (SM) at the recommended optimum densities and intercropped at farmers' planting densities under two levels of soil fertility. Infiltration rates were generally high, with an overall mean in the porous sandy soil of 17 cm h-1. Deep drainage losses accounted for 15 f annual rainfall in a low rainfall season (1995) and an estimated more than 20 n the wet 1994 season. Additional top dress NPK fertilizers (OM IF) to cereals prior to the commencement of reproductive stages, increased soil water extraction in the intercrops in the drier year, for which soil water status was, therefore, higher in plots where only organic manure (OM) was applied. The relatively higher annual rainfall in 1994 generally increased soil water use. Later maturity of sorghum in the M–S–C intercrop increased WU of this cropping system, particularly in 1995. SM produced significantly (P<0.01 in 1994 and P<0.05 in 1995) higher total dry matter (TDM) than the intercrops, a trend shown over the complete growing season most of the time, with the exception of OM SM in 1995. The total grain yield was significantly (P<0.01) higher in SM in the wet 1994 season. Millet, particularly when intercropped, used water more efficiently for grain production in 1995 along with other limiting resources. It showed better adaptation to moisture stress by producing similar (P=0.79) harvest indices (HIs) in sole and intercropped millet. HIs of the sole cereals and the OM M–C were relatively higher in the 1995 than in the wet 1994 seaso