No abstract

Drought and heat-tolerant crops, such as Pearl millet (Pennisetum glaucum), are priority crops for fighting hunger in semi-arid regions. Assessing its performance under future climate scenarios is critical for determining its resilience and sustainability. Field experiments were conducted over two consecutive seasons (2015/2016 and 2016/2017) to determine the yield responses of the crop (pearl millet variety "Okoa") to microdose fertilizer application in a semi-arid region of Tanzania. Data from the experiment were used to calibrate and validate the DSSAT model (CERES Millet). Subsequently, the model evaluated synthetic climate change scenarios for temperature increments and precipitation changes based on historic observations (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018). Temperature increases of +0.5 to +3.0 • C (from baseline), under non-fertilized (NF) and fertilizer microdose (MD) conditions were used to evaluate nine planting dates of pearl millet from early (5 December) to late planting (25 February), based on increments of 10 days. The planting date with the highest yields was subjected to 49 synthetic scenarios of climate change for temperature increments and precipitation changes (of −30% up to +30% from baseline) to simulate yield responses. Results show that the model reproduced the phenology and yield, indicating a very good performance. Model simulations indicate that temperature increases negatively affected yields for all planting dates under NF and MD. Early and late planting windows were more negatively affected than the normal planting window, implying that temperature increases reduced the length of effective planting window for achieving high yields in both NF and MD. Farmers must adjust their planting timing, while the timely availability of seeds and fertilizer is critical. Precipitation increases had a positive effect on yields under all tested temperature increments, but Okoa cultivar only has steady yield increases up to a maximum of 1.5 • C, beyond which yields decline. This informs the need for further breeding or testing of other cultivars that are more heat tolerant. However, under MD, the temperature increments and precipitation change scenarios are higher than under NF, indicating a high potential of yield improvement under MD, especially with precipitation increases. Further investigation should focus on other cropping strategies such as the use of in-field rainwater harvesting and heat-tolerant cultivars to mitigate the effects of temperature increase and change in precipitation on pearl millet yield.

This article deals with technology transfer from science to agriculture with pearl millet (Pennisetum glaucum (L.)R.Br.) in central Tanzania as example. The major question is which validity recommendations from different types of field experiments have and how geo-information (i.e. soil and landscape position) can lead to more site-specific recommendations. Tied ridging and reduced amounts of placed fertilizer during sowing were tested to increase yields on researcher-managed plots on-station, demonstration plots in villages, and farmer-managed plots on-farm. While on-station trials provided potential yield effects, physical distance to the station and differing conditions led to a higher informational value of village plots that mirror the context of local farmers. The treatments often resulted in significant yield increase. Soil and relief information and distance to settlements (i.e. gradient of management intensity) are key factors for data variability in on-farm trials. Unexplained variability is introduced through leaving degrees of freedom with respect to management to the farmer. Apart from soil and physiographic information, the latter should be part of a detailed data collection procedure in agronomic trials in large numbers addressing Sub-Saharan smallholder farming. Balanced data sets with dispersed trials on crucial soil and relief units are essential for future research.

Inadequate knowledge on appropriate number of nodes of sweet potato vines to be planted and sources of potassium fertilizer to be used are among major factors resulted into low sweet potato productivity in central part areas of Tanzania. This research aimed at evaluating the effects of four levels of nodes buried and three potash fertilizer sources on growth and yield of three sweet potato varieties. Split-split plot field experiment in complete randomized block design was conducted at Hombolo, Dodoma during 2013/2014 cropping season. Main plot were three sweet potato varieties, Kiegeya, Mataya, and Ukerewe. Sub plot were, four level of buried nodes, (two above ground), five buried nodes (three above ground), seven buried nodes (three above ground) and eight buried nodes (four above ground). The sub -subplot treatments were potash fertilizer sources i.e control no fertilizer used, Potassium chloride (KCl), Potassium nitrogen phosphate (NPK) and Farm yard manure (FYM). Results indicated that there were no significant effects on the yield among varieties used. The number of tubers increased significantly in fertilized plots compared to control. The lowest number of tuber roots (3 tubers) was from control treatment while the highest number of tuber roots (6) was from KCl treatment. The effect of potassium fertilizer sources on root yield were also significant, use of KCl resulted to highest yield (18.84 t ha -1 ), followed by NPK (17.51 t ha -1 ), FYM (11.33 t ha -1 ) and control treatment where no fertilizer applied (8.82 t ha -1 ). Plating of different number of nodes resulted into significant increase in yield where the highest yield of (15.91 t ha -1 ) was from eight buried nodes and lowest total yield (11.68 t ha -1 ) was from four buried nodes. Seven and eight buried nodes with KCl and NPK fertilizers appeared to be appropriate for optimum sweet potato growth, yield and tuberous root quality in the study area and are therefore recommended.