Examining the Impact of Polyacrylamide and Other Soil Amendments on Soil Fertility and Crop Yield in Contrasting Agroecological Environments

This study aims to investigate the effects of polyacrylamide (PAM) alone or integrated with other soil amendments on soil fertility and Teff (Eragrostis tef (Zucc.) Trotter) yield. A field experiment was carried out for 2 years in three contrasting agroecological zones of the Upper Blue Nile basin, Ethiopia, using a randomized complete block design with 3 replicates. The amendments applied were PAM (40 kg ha−1), biochar (B, 8 t ha−1), lime (L, 4 t ha−1), gypsum (G, 5 t ha−1), farmyard manure (FYM, 5 t ha−1), PAM + B, PAM + L, and PAM + G, and control. The results showed that PAM + L, PAM + B, and L treatments noticeably improved pH, available phosphorus (Pav), total nitrogen (TN), organic carbon, and water infiltration in the Aba Gerima and Guder soils, whereas the PAM + B, B, and FYM treatments expressively increased soil water content, Pav, and TN in the Dibatie soil. Likewise, compared with the control, teff yield significantly (p < 0.05) increased by about 25 to 37% at Guder, 25 to 32% at Aba Gerima, and 20 to 31% at Dibatie. The partial-budget analysis showed that PAM + L at both Guder and Aba Gerima, and PAM + B at Dibatie were more profitable, with net benefits of 1056, 1663, and 1975 USD ha−1, respectively. Applying PAM in combination with lime on moderately to strongly acidic soils, and with biochar on slightly acidic soils could have a synergistic effect, leading to improved soil properties and crop yield.