Landscape positions dictating crop fertilizer responses in wheat-based farming systems of East African Highlands

Amede, Tilahun; Gashaw, Tadesse; Legesse, Gizachew; Tamene, Lulseged; Mekonen, Kindu; Thorne, Peter; Schultz, Steffen

doi:10.1017/s1742170519000504

Cited by 30 publications

(57 citation statements)

References 38 publications

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“…There is a wide variability in actual crop yields (Affholder et al, 2013) within smallholder agricultural landscapes attributed to soil and topographic variations (Amede et al, 2020;Diarisso et al, 2016;Tamene et al, 2017). The yield variability is also associated with resource availability and nutrient use efficiency (Tittonell et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Sorghum yield response to NPKS and NPZn nutrients along sorghum-growing landscapes

Desta¹,

Amede²,

Asrat³

et al. 2022

Ex. Agric.

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Summary Grain sorghum [Sorghum bicolor (L.) Moench] is the major cereal crop used as staple crop in the arid and semi-arid regions of Ethiopia. Low sorghum yields are attributed to soil, climate and topographic factors. We investigated sorghum yield response to factorial combination of nitrogen and phosphorous (NP) as well as potassium (K), sulphur (S) and zinc (Zn), and how the position of farmers’ fields belonging to different landscape positions (i.e., upslope, mid-slope, and foot slope) could explain fertilizer response and yield variability. The analysis in this study made use of dataset from two sets of on-farm experiments where trials were set at two farmers’ fields for NPKS and three farmers’ fields for NPZn experiments in each landscape position. The experiments were implemented at two sorghum-growing locations (i.e., Hayk and Sirinka) in parts of the north-eastern Amhara region in Ethiopia. Sorghum yield response to fertilizer application was strongly linked to the spatial variation along landscape positions and varied over locations. Fertilizer response was significantly higher at foot slopes compared to mid-slopes and upslope positions, where fields at foot slopes exhibited relatively homogeneous responses. Application of combined nitrogen (N) and phosphorus (P) fertilizers, landscape position and the interaction of fertilizer application and landscape positions strongly affected sorghum yield. There was a linear and significant increase in sorghum yield with the increase in the NP rates. The combined application of NP with different levels of KS as well as NP with Zn fertilizer rates did not result in significant yield difference. The results indicated that local factors were much more influential when accounting for the heterogeneity in sorghum yield response to fertilizer. This further acknowledges the importance of a landscape-based fertilizer management approach to respond yield potential variability related with the farmers’ fields and landscape environment. Further investigation is needed to develop homogeneous fertilizer response units based on spatial variability of soil and topographic attributes along the landscape.

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Section: Introductionmentioning

confidence: 99%

Sorghum yield response to NPKS and NPZn nutrients along sorghum-growing landscapes

Desta¹,

Amede²,

Asrat³

et al. 2022

Ex. Agric.

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“…And though the AEZ-based approach provided relatively refined fertilizer recommendations, it did not take into account the several micro-factors that influence crop response to nutrients, and hence still results in a coarse recommendation that can lead to sub-or supraoptimal fertilizer applications for farmers. Amede et al (2020) showed the effect of local-scale topography on yield response to fertilizer, and developed a topography-based fertilizer recommendation. However, this approach, too, has ignored other important sources of fertilizer response determinants and hence is not suited for holistic, site-specific fertilizer recommendations.…”

Section: Introductionmentioning

confidence: 99%

A data-mining approach for developing site-specific fertilizer response functions across the wheat-growing environments in Ethiopia

et al. 2022

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Summary The use of chemical fertilizers is among the main innovations brought by the 1960s Green Revolution. In Ethiopia, fertilizer application during the last four decades has led to significant yield gains, yet yield remains below its potential across much of the country. One of the main challenges responsible for low yield response to fertilizer application has been the use of ‘blanket’ recommendations, whereby no tailoring of fertilizer amount and frequency is done based on soil requirements. As a result, the amount of fertilizer applied ranges widely, and can be either sub- or supra-optimal. There is thus an increasing need for site-specific fertilizer recommendations which take into account site characteristics such as climate variables (temperature, rainfall, and solar radiation); soil factors (soil organic carbon, moisture, pH, texture, cation exchange capacity, and level of macro- and micronutrients); and topographic position indices. This article reports on a data-mining approach we developed on a large dataset of 6585 wheat (Triticum aestivum) field trials. The dataset includes detailed, site-specific biophysical variables to create nutrient response functions that can guide optimal site-specific fertilizer application. The approach used a machine-learning model (random forest) to capture the relationship between nutrients – nitrogen (N), phosphorous (P), potassium (K), and sulfur (S) – and wheat yield. The model explained about 83, 82, 47, and 69% of variances of yield for N, P, K, and S omission, respectively, with consistent performance across training and testing datasets. Expectedly, for N and P omission data, the most important explanatory variables are nutrient rate, followed by soil organic carbon and soil pH. For K and S, however, climatic variables played an important role alongside nutrient rates. The site-specific yield–fertilizer response curves derived from our model are highly variable from location to location, as they are affected by the climatic, soil, or topographic conditions of the site. Importantly, using principal component analysis, we showed that the shape of the fertilizer response curves is a result of the multiple environmental factors (including soil, topography, and climate) that are at play at a given site, rather than of a specific dominant one. The research output is expected to respond to the national policy demands for a sound method to identify the optimal fertilizer rate to increase economic returns of fertilizer investments and take fertilizer utilization research one step further.

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“…Hoque et al (2016) also noted that the depletion of soil organic matter is mainly caused by high cropping intensity, especially monocropping, increased use of nutrient demanding varieties, limited availability and use of crop residues, and limited practices of green manure-based cropping patterns. Even in a situation where farmers are applying higher rates of fertilizers in nutrient depleted soils and upslope farms of the Ethiopian highlands, the nutrient use efficiency and the return per investment is very low (Amede et al, 2020), making these degraded soils nonresponsive (Vanlauwe et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Short term fallow and partitioning effects of green manures on wheat systems in East African highlands

Amede

Legesse

Agegnehu

et al. 2021

Field Crops Research

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Soil fertility depletion is a major constraint of smallholder farming in sub-Saharan Africa. We tested the aftereffects of green manures, namely vetch (Vicia sativa L.), lupin (Lupinus polyphyllus L.), and lablab (Lablab purpureus L.) incorporated into the soil compared to three fertilizer levels (0/0, 23/0, and 78/20 kg N/P ha − 1 ) and evaluated their effect on soil fertility status and wheat yield in acidic Nitisols of southern Ethiopia, for three consecutive years (2017)(2018)(2019). The treatments were laid out in a randomized complete block design with three replications. In 2017 and 2018, green manures were sown in March and April, respectively, using short rains and incorporated into the soil during late flowering stage, either (i) the whole shoot and root biomass were plowed under, (ii) shoot biomass was transferred to non-treated plots or (iii) only the below ground root biomass was used. Wheat was sown during long rains during the same growing season a month after the incorporation of green manures. In 2019, wheat was grown on the residual plots with the application of an additional 64/20 kg N/ P ha − 1 . Results revealed that in 2017 and 2018 the application of vetch and lupin green manure resulted in grain yield advantages of 49 and 32 % and 34 and 19 %, respectively, over 0/0 and 23/0 kg N/P ha − 1 , though it produced less grain yield compared to higher fertilizer rates. In 2019, the addition of vetch and lupin whole biomass treatments gave significantly higher wheat yield over fertilizer treatments, with yield advantages of 18-26 %. Similarly, root biomass only also produced a significantly higher yield than fertilized plots. The yield benefits from green manures were due to improved soil water content, improved P-availability, significantly increased exchangeable K, Ca, and Mg, and increased pH by about 0.5 units. The residual effect of green manures could compensate for up to 33 % of the recommended rate of 78 N kg ha − 1 . We conclude that niche-based integration of green manures could improve yield, enhance soil carbon sequestration and sustain croplivestock systems, whereby the above ground biomass could serve as quality livestock feed without compromising soil fertility benefits.

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Landscape positions dictating crop fertilizer responses in wheat-based farming systems of East African Highlands

Cited by 30 publications

References 38 publications

Sorghum yield response to NPKS and NPZn nutrients along sorghum-growing landscapes

Sorghum yield response to NPKS and NPZn nutrients along sorghum-growing landscapes

A data-mining approach for developing site-specific fertilizer response functions across the wheat-growing environments in Ethiopia

Short term fallow and partitioning effects of green manures on wheat systems in East African highlands

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