International Journal of Plant & Soil Science

A three-year study to determine the initial and residual effects of inorganic and organic fertilizers on potato (Solanum tuberosum L.) and subsequent quinoa (Chenopodium quinoa, Willd) crop performance was conducted in four indigenous communities in the central Bolivian Andean Highland region starting in 2006. The objectives of this research were to identify conventional and alternative fertilizers and combinations of those nutrient sources that improve potato growth and yields and to assess the residual effect of nutrient amendments applied to a previous crop on quinoa as a subsequent crop in the rotation. On-farm trials using local crop management practices had an unfertilized control and separate and combined treatments of local conventional and alternative organic sources (i.e., composted cow and sheep manure, household/urban compost and Biofert, a solid biofertilizer), and inorganic fertilizer (diammonium phosphate + urea). Treatments including inorganic fertilizer alone or combined with cow and sheep manure significantly increased potato tuber yields 67, 68, 79 and 74% over the yield observed in the control plots. The residual effect of these treatments also increased quinoa grain yield 61, 58, 44 and 58% over that of the control. These results are possibly due to the more rapid nutrient availability of applied inorganic fertilizers compared to the application of organic amendments. Increased use of inorganic fertilizers in this region may be necessary because of the reduced availability of organic amendments and the need for improved crop production in both the initial potato crop and subsequent quinoa phase of the crop rotation that depends on residual soil fertility.