Abstract

Decline in farmland soil fertility due to nutrient depletion is a concern for smallholder farmers in the highlands of Ethiopia. In this study we tested if long-term addition of compost, either alone or in combination with nitrogen (N) and phosphorous (P) fertilizer, affected available soil nutrient status, grain/tuber harvests, agronomic N use efficiency, and plot level N and P nutrient balances. The on-farm experiments were conducted on four farm fields for up to 6 years in Beseku, Ethiopia. A randomized complete block design was used, with four treatments: full dose of compost applied alone at 2.4 t ha(-1) DW organic matter (C); full dose of fertilizer (F); half compost and half fertilizer (CF); and, unfertilized control. In the upper 10 cm of the surface soil, several Mehlich-3 extractable nutrients (B, Ca, K, Mg, P, S, and Zn) had significantly higher concentrations in the C treatment (P < 0.01), and some in the CF treatment (P < 0.05) than in the control. Phosphorus was the only nutrient with a higher concentration in the F treatment than the control. Maize and faba bean showed added benefits (synergy) in terms of yield increase in the CF treatment and a better agronomic efficiency for added N. Plot level N balances were negative for all treatments except C, with strong depletion in the control (-76 kg N ha(-1) yr(-1)) and F (-65 kg N ha(-1) yr(-1)) treatments. When the N balance was compared to measured change in soil N, the F and control treatments were significantly (P < 0.05) lower than zero. N in the CF and C treatments was close to steady-state, i.e., the input of N in organic matter compensated for the loss of N through mineralization. The control treatment had a negative P balance of 11 kg P ha(-1) yr(-1), with moderately negative balance of 4 kg P ha(-1) yr(-1) in the C treatment. The CF and F treatments had positive P balances. Thus, the addition of compost, both alone or in combination with mineral fertilizer, can prevent N and reduce P mining and improve the nutrient status of the soil. When only NP fertilizer was used, the crop utilized all N that was mineralized indicating that the crop was N limited. (C) 2015 Elsevier B.V. All rights reserved.

Keywords

Soil fertility; Compost; Nutrient balance; Micronutrients; Macronutrients; Ethiopia

Published in

Agriculture, Ecosystems and Environment
2016, Volume: 218, pages: 220-231
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Chala, Workneh Bedada

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Karltun, Erik

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss


UKÄ Subject classification

Soil Science


Publication identifier

DOI: https://doi.org/10.1016/j.agee.2015.11.024

Permanent link to this page (URI)

https://res.slu.se/id/publ/71873