Biosolids with different loading rates were applied to soil planted with rainfed barley to study the effects of applying biosolids on soil and on barley’s straws and grains yield. Randomized Complete Block experimental design was employed with 5 treatments. This included a control and four replicates to test the null hypothesis which states that there is no significant difference between treatment means on crop and soil parameters vs. the research hypothesis which states applying biosolids to land planted with rain-fed barley affects both soil and crop parameters. Biosolids loading rates were 0 as a control, 2, 4, 6, and 8 metric tons/ha. Soil at the testing site had a high clay content in the sub-soil and relatively lower clay content on the surface, probably due to wind erosion. The soil was slightly calcareous with lime content increasing with depth and with a slight alkalinity. Organic matter and phosphorus contents of soil were low with colors that varied from reddish brown to yellowish brown. At harvesting time, there was no significant differences in grain yields at different biosolids loading rates with a p-value of 0.52. Average grain yields of 2.86, 3.37, 3.4, 3.57, and 3.20 tons/ha were measured at biosolids loading rates of 0, 2, 4, 6, and 8 tons/ha, respectively. Average grain yield of 3.00 for a recommended inorganic fertilizer rate of diammonium phosphate and Urea traditionally applied at rates of 90 kg/ha and 20 kg/ha, respectively, showed a yield higher than the 0 biosolids loading rate. However, it was lower than all other biosolids loading rates. It was determined that applying biosolids to soils planted with rain-fed barley significantly increased straw yield and straw protein content. No significant increase in grain yield or in grain protein content was measured. It was also determined that a statistical significant decrease in the thousand grain weight occurs as biosolids loading rates increased with a p-value <0.000001. This has negative effects on barley’s grain quality. No significant increase in heavy metals in the crop or the soil was observed in the biosolids treated plots. However, increases in soil organic carbon, total Kjeldahl nitrogen and salt concentrations were increased with increasing biosolids loading rates. The null hypothesis tested in this study showed that applying biosolids to soils planted with rain-fed barley had positive effects on the crop with no effects on the soil in comparison with no application of biosolids and the application of inorganic fertilizer.
ASJC Scopus subject areas
- Environmental Chemistry
- Environmental Engineering
- Waste Management and Disposal