No abstract

The relatively poor accessibility, high costs, long turnaround time for analysis, and lack of information about soil and plant testing in the Andean highland region (Altiplano) of Bolivia has hampered informed and timely nutrient management decisions for potato (Solanum tuberosum L.) crops. The objective of this study was to determine if the Cardy nitrate meter (Horiba Ltd., Kyoto, Japan), a low-cost, portable, and rapid field test method, could be used to improve nitrogen (N) fertility management among isolated rural indigenous communities at different elevations in this rugged semi-arid environment. Fully matured leaf petioles were sampled at blooming time from potato trials established in three communities during the 2006-2007 and 2007-2008 growing seasons. Those trials were composed of 12 fertility treatments (i.e., an unfertilized control and different combinations of sheep and cow manure, inorganic fertilizer, commercial household/urban compost, and a commercial microbial activator soil amendment) arranged in a randomized complete block design with four replications. In general, in both growing seasons and in all communities, nitrate measured in the sap of leaf petioles by the Cardy meter had relatively low but significant correlations with leaf petiole total N (ranging from r 2 = 0.07 to r 2 = 0.60 across seasons and communities) and with total fresh tuber yield (ranging from r 2 = 0.11 to r 2 = 0.50 across seasons and communities). However, some problems were encountered with being able to consistently calibrate the meter with supplied standards prior to each use of the meter. These results indicate that the Cardy ion meter might be an effective tool for potato growers or agricultural professionals working in the Altiplano of Bolivia if further research can be conducted to determine if the meter is consistent for diverse sites in the Altiplano and is practical for the cultural, economic, and environmental conditions of the region.

The objective of this study was to determine the effects of applications of organic and inorganic soil amendments on initial and residual soil chemical, physical and biological properties that may affect both short-and long-term soil fertility in a potato (Solanum tuberosum L.)-based cropping system of indigenous rural communities in the Bolivian Andean Highlands (Altiplano). Field experiments were conducted in four representative low and high elevation communities in the semi-arid Central Andean Region of Bolivia from 2006 to 2009. Treatments included a control, and applications of sheep and cow manure, a commercial household/urban compost product, a commercial biofertilizer soil amendment, urea and diammonium phosphate and combinations of these different treatments. Soil samples were taken from all the sites prior to application of treatments and planting of potatoes as well as during the growing season and prior to planting of a

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 Original Research Articleincreased 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.