ASSESSMENT OF SOIL CHEMICAL PROPERTIES OF OKE-OYI IRRIGATION SCHEME FOR SUITABILITY OF AGRICULTURAL PRODUCTION

Abstract

Irrigation applications have impacts on soil properties and these impacts may be negative on soil, crop and 
groundwater quality. This could be as a result of the quality of water used, method of application and the nature of the 
soil viz the chemical composition of the soil. Soil quality analysis at phase 1I of Oke-Oyi irrigation scheme was carried 
out in the study. Twelve soil sampling points were considered from different locations around the irrigation scheme. 
Soil samples were collected at the rooting depths (0-20, 20-60 and 60-100cm) of the crops planted making a total 36 
samples. The soil samples were collected in October, 2020 through September, 2021 using soil auger. A random 
sampling method was used to sample soil and the soil samples were taken to the laboratory for chemical analysis. The 
chemical analysis results revealed that the soil pH of the baseline data (2013) and the field data were moderately acidic 
to neutral. The pH of both baseline (2013) and field data ranged from 5.30 to 6.87 and 5.12 to 6.81, respectively. The 
average organic carbon (OC) for both baseline and field data ranged from 0.14 to 0.27% and 0.12 to 0.20% of the 
entire soil nutrients relating to soil fertility. There is a little decrease in the level of organic carbon compared with the 
baseline data. Available phosphorous content of the soil is high and larger from 20.276 to 28.342mg/l for the baseline 
data (2013) and for the field data, it ranged from 18.20 to 22.01mg/l. Sodium, which determines the sodicity status of 
a soil is generally low for both baseline and field data, and ranged from 0.15 to 0.65me/l and 0.12 to 0.47me/l, 
respectively. The exchangeable sodium percentage (ESP) value of both baseline and field data ranged from 5.90 to 
10.0% and 2.63 to 9.06%, slightly decreased for both data. The calcium in the soils is generally moderate and ranged 
from 4.36 to 6.22me/l and 2.86 to 4.16me/l for both baseline and field data, respectively. Magnesium which has been 
the dominant cation in the study ranged from 1.16 to 2.26me/l and 1.09 to 2.11me/l for both baseline and field data. 
The organic matter of the soil is moderate for both baseline and field data, ranging from 0.13 to 0.17% and 0.11 to 
0.16%, respectively, due to rapid rate of organic matter decomposition as a result of available moisture during 
irrigation. The cation exchange capacity (CEC) of the soil for both data ranged from 4.76 to 5.52me/l. The sodium 
adsorption ratio (SAR) ranged from 0.10 to 0.32 meg/l. In 2011, rice yield decreased from 85,000 kg to 77,000 kg in 
2012 and subsequently, decreased to 70,000 kg in 2013. Therefore, the study concluded that there is a need for proper 
monitoring of the soil condition in the irrigation scheme to prevent further deterioration of the soils since some changes 
have been observed compared to the baseline data.