Effects of Soil Salinity on Agronomics Performances of Onion (Allium cepa L.) Varieties Cultivated in Tahoua Region, Niger

Soil salinity is a major constraint for irrigated agriculture, particularly in vegetable crop production such as onion crops.The main objective of this study is to evaluate the effects of soil salinity on the agronomic performance of onion varieties cultivated in the Tahoua region of Niger country.The study, conducted using block factorial design on soil pots, tested 3 varieties of onion (V1=local variety, V2=Perma variety, and V3= purple Galmi variety) with four (04) levels of soil electrical conductivity, EC (S0=control soil; S1=soil with EC of 4 dS/m, S2=soil with EC of 8 dS/m, and S3=soil with EC of 12 dS/m) to assess growth of onion plants as well as biomass and bulb yields.The results showed that the number of leaves, height, and diameter of onion plants decreased with increasing soil salinity levels under all varieties.Furthermore, an early cessation of growth evolution by plant wilting was observed on soil with high salinity (S3, CE=12 dS/m) at 60, 48, and 56 days after transplanting (JAR) under V1, V2, and V3 respectively.In addition, onion bulb yield, between 896 and 8000 kg/ha, decreases significantly with the increase in soil EC.Compared to control soil salinity (0.68 dS/m), an increase in soil salinity levels (3-16 dS/m) caused a reduction in onion bulb yield of 43 to 88%, particularly under local (V1) and Galmi violet (V3) varieties.Under local variety, bulb yield under control soil (7832.0kg/ha) is respectively 3.2 and 8.7 times higher than that under S1 (2406.2kg/ha) and S2 (896.4kg/ha).However, V2 appears to be more tolerant to soil salinity than V1 and V3 in plant growth and bulb production.Thus, this study shows that soil salinity is a threat to onion crop production in Niger.