Teff Grain Physical and Chemical Quality Responses to Soil Physicochemical Properties and the Environment

Abstract

Teff is the only cultivated cereal crop from the genus Eragrostis and it is the major staple food of Ethiopians. In Ethiopia, the quality of teff and its market price are primarily determined by its grain color. The objective of this study was to evaluate the effects of soil physicochemical characteristics across multiple locations in the two main teff growing regions of Amhara and Oromia states in Ethiopia on teff grain color and nutritional quality of a single variety. Grain and soil samples were collected from 24 field sites cultivated with the popular teff variety ‘Quncho’ (DZ-Cr-387/RIL-355). The teff grain samples collected from the 24 locations were evaluated for grain color, proximate composition, amino acid composition, and grain mineral concentration and the soil samples were analyzed for their physicochemical properties. Sample location means were considered different p < 0.05. Teff grain color indices of hue (H), saturation (S), and brightness (V), grain proximate composition, amino acid composition, and mineral concentration differed among locations (p < 0.05). There were significant negative correlations between grain S color value and soil pH, SOC, Ca, Mg, S, and Na. Soils with greater pH, SOC, Ca, Mg, and S generally had lower S values and thus, whiter color teff grains. There were considerable variations in the measured parameters for soil and teff grain physicochemical properties. The results indicated an opportunity for management interventions necessary to obtain uniformity in grain color and chemical composition for the same variety of teff grown in the two major regions in Ethiopia.

1. Introduction

Teff [Eragrostis Tef (Zucc.) Trotter] is the only cultivated cereal crop from the genus Eragrostis [1,2,3,4]. It is believed that pre-semantic inhabitants of the Ethiopian highlands domesticated teff around 4000 BC as a food crop [1,5,6] and it has served as the major staple food for Ethiopians for thousands of years.

In Ethiopia, the main teff-producing areas have been concentrated in the Amhara and Oromia regional states (the northwestern and central highlands of Ethiopia). Teff cultivation in Amhara and Oromia regional states covered 1.45 (47.8%) and 1.14 million ha (37.6%) of land, respectively, for a combined 2.59 million ha or 87.5% of the total teff cultivation in Ethiopia during the 2017 to 2018 main growing season [7]. Teff grain production from these two main cultivated regions of Amhara and Oromia states were 2.6 (48.9%) and 2.04 million tons (38.6%), respectively, for a total of 4.64 million tons or 87.5% of the total teff production in Ethiopia during the 2017 to 2018 main growing season [7]. Teff grain production ranged from 0.84 to 1.75 tons per hectare annually in Ethiopia depending on location of cultivation and agronomic practices [7]. Almost all the teff grain produced in Ethiopia is mainly used for local consumption in the form of “injera” (a thin, malleable, with many eyes, fermented bubbly spongy type Ethiopian bread) [8].

The major determinants of quality variation of cereal grains are derived from the nutrient composition and physical attributes of the grain [9]. The grain color of teff varies from pale white to ivory white, light tan to dark brown to reddish-brown purple [10,11,12] and in Ethiopia, the quality of teff grain is determined primarily by its physical attribute of color [13,14]. There are four major categories of teff grain colors specified by the Ethiopian Standard Agency (ESA) and the grains are classified as very white (magna), white (nech), mixed (sergegna) and brown (key) teff [13]. In Ethiopia, grain color is a measure of quality that also dictates the market demand and value. The very white and white teff fetches the highest price and is consumed by the wealthiest individuals whereas, the brown teff is sold at a lower price to low-income communities [8,15,16,17]. In Ethiopia, the production area and soil type which is closely correlated with grain color, are intricately linked to the market price of teff grain [8,18,19]. For example, teff cultivated on black and brown soils in Ethiopia has brighter grain color than those produced on red soils and are most preferred by consumers and traders [19]. However, even with the same grain color, there has been a wide range of variability in the nutrient content reported for teff [20,21,22].

Further, teff has been proposed as an important dietary source of mineral nutrients to combat malnutrition for the populace of developing nations [22]. In particular, the concentrations of calcium, iron, copper, zinc, carbohydrates, and fiber are generally greater than those of other cereal crops [21,23]. Micronutrients such as iron and zinc are considered the most limiting nutrients for children in many communities in developing countries [24] and teff may be the ideal crop for biofortification as a sustainable and cost-effective strategy to curtailed micronutrient malnutrition that affects approximately 2 billion people globally [25,26]. Further, among female athletes from developing nations, only Ethiopian athletes are free of anemia and this was attributed to the consumption of teff [27]. Teff has the potential in reducing iron deficiency anemia diseases by its iron richness [21,28,29] and it is also reported to have a complete set of essential amino acids with excellent composition [21,30,31,32,33] and richer in lysine than most other cereals [34].

The qualitative value of teff as a gluten-free grain combined with its nutritional value and health benefits have attracted global interest in its consumption [14,35,36,37]. Compared to the other major cereal crops, the crude protein, crude fiber, fat and starch concentrations of teff grain are either similar or superior to those of maize, oat, sorghum, wheat and quinoa (false cereal) in general [38]. Globally, the demand for teff grain has increased over the last decade due to the many health benefits of this gluten-free product and as a result of the demand, the Ethiopian government has prohibited the export of teff grain raw material to ensure food security and protection of local markets in Ethiopia. However, the government of Ethiopia did not place a ban on value-added teff hence, teff bread (injera) is exported to the Middle East, Europe, and the United States of America [39].

It is possible that the reported variability in the nutrient content of teff in Ethiopia could be attributed to environmental factors (climatic and edaphic variations) rather than genetic variations. However, there are no studies that have reported on the influence of different environmental factors on variability in teff grain quality in Ethiopia. Most reported research focused on teff nutritional quality based on color [21,22,30,40] and did not address the influence of environmental factors on grain nutritional composition. Therefore, the objective of this study was to evaluate the effects of soil physicochemical characteristics across multiple locations in the main teff growing regions of Ethiopia on teff grain color and nutritional quality of a single variety.

2. Materials and Methods

2.1. Description of the Study Area

This study was carried out in 24 major teff producing areas of Amhara and Oromia regional states of Ethiopia (northwestern and central highlands of Ethiopia, respectively). The specific locations and known names listed in parentheses were Abrja (Denbia), Abshem (Debre-Elias), Adet 1, Adet 2, Akaki, Alemtena, Arerti 1 (Minjar), Arerti 2 (Minjar), Atsedemariam (Este), Bichena, Birzakani (Metekel), Bishoftu (Ad’a), Bitiejersalafo (Welenkomi), Demdengay (Gonj-Kollela), Fetlokuskuam (Yilmana Densa), Gejagedanba (Sebeta), Gumdri (Dangila), Simada (Simada), Kosheshila (Shebel), Kudmi (Mecha), Motta, Wondata (Bahir Dar), Yubodegabati (Dedi), and Zenzelima (Bahir Dar) (Figure 1).

The areas were selected based on their variability of altitude (1670–2570 m above sea level), soil types (Nitisols–Vertisols), annual rainfall amount (1000–1960 mm) and temperatures (

Table 1. Altitude, rainfall, minimum and maximum temperatures of the two main teff growing regions of Amhara (northwestern highlands) and Oromia (central highlands) in Ethiopia.

Region	Soil Type	Sites	Met Station	Altitude (m)	Annual Rainfall (mm)	Temperature (°C)
						Maximum		Minimum
						max	Ave	min	average
Amhara	Vertisols	Abrja	Gorgora	1852	1153	36.5	25.2	6.5	11.4
Amhara	Nitisols	Abshem	D/Elias	2234	2291	32.4	24.5	7.0	14.2
Amhara	Nitisols	Adet 1	Adet	2207	1372	35.5	26.8	3.0	11.0
Amhara	Vertisols	Adet 2	Adet	2174	1372	35.5	26.8	3.0	11.0
Oromia	Vertisols	Akaki	Akaki	2205	979	32.0	26.7	1.0	10.3
Oromia	Vertisols	Alemtena	Alemtena	1652	809	37.2	29.4	1.0	14.1
Oromia-Amhara	Vertisols	Arerti 1	Arerti	2152	957	35.0	28.1	4.0	13.6
Oromia-Amhara	Vertisols	Arerti 2	Arerti	2152	957	35.0	28.1	4.0	13.6
Amhara	Vertisols	Atsedemariam	Este	na †	na	na	na	na	na
Amhara	Vertisols	Bichena	Bichena	2543	1130	33.0	23.7	5.0	11.5
Amhara	Regosols	Birzakani	Chagni	1677	1856	36.2	28.6	3.0	13.4
Oromia	Vertisols	Bishoftu	Bishoftu	1887	779	39.5	27.0	−1.0	11.5
Oromia	Vertisols	Bitiejersalafo	Wolenkomi	897	na	na	na	na	na
Amhara	Regosols	Demdengay	Adet	2261	1372	35.5	26.8	3.0	11.0
Amhara	Vertisols	Fetlokuskuam	Adet	2192	1372	35.5	26.8	3.0	11.0
Oromia	Vertisols	Gejagedanba	Sebeta	2148	917	na	na	na	na
Amhara	Nitisols	Gumdri	Dangla	2218	1848	32.0	25.5	−1.5	10.5
Amhara	Vertisols	Kosheshila	Bichena	2389	1130	33.0	23.7	5.0	11.5
Amhara	Nitisols	Kudmi	Merawi	1977	1580	33.0	na	2.0	na
Amhara	Nitisols	Motta	Motta	2419	1286	32.2	24.5	1.5	10.4
Amhara	Vertisols	Simada	Simada	2574	1017	32.1	na	2.5	na
Amhara	Vertisols	Wondata	Bahir Dar	1816	1491	38.5	28.4	0.4	12.7
Oromia	Vertisols	Yubodegabati	Dedi	2172	897	na	na	na	na
Amhara	Nitisols	Zenzelima	Bahir Dar	1920	1407	38.5	28.4	0.4	12.7

† na, not available.

). Maximum temperatures range from 39.5 °C at Debre Elias to 29 °C at Motta with a minimum temperature of 9.8 °C at Debre Elias to −1.5 °C at Dangla. Rainfall amount varies from 1964 mm (Debre Elias) to 779 mm (Bishoftu) (Table 1). The areas were also selected from the two regions based on the information gained from Addis Ababa and other regional markets surveyed [19] and from personal communication with researchers and zonal agricultural experts.

2.2. Data Collection, Grain and Soil Nutrient Analysis

At each of the 24 field sites, the popular teff variety named ‘Quncho’ (DZ-Cr-387/RIL-355) was earmarked for grain collection due to its white grain color, adaptability to the different agro-ecological zones, and its widespread cultivation across Ethiopia [41]. The recommended fertilizer rate for Vertisols, in Ethiopia, is 60 kg N and 80 kg P₂O₅ ha⁻¹ by Debre Zeit Agricultural Research Center and for Nitisols (red soils), is 40 kg N and 60 kg P₂O₅ ha⁻¹ by Adet Agricultural Research Center (AARC) in Ethiopia. Diammonium phosphate (DAP) and urea fertilizer materials are the typical sources of the nutrients. While DAP is usually applied once at the time of sowing, split application of urea is the general N management practice, one half at sowing and the other at early tillering. However, in the study areas, the extent to which farmers follow these fertilizer recommendations is not verifiable.

Grain sampling was carried out at each of the selected field site (approximately 1 ha in size) and a total of five 1-m² quadrat samples were collected randomly along a diagonal transect across the field at fixed steps intervals at the time of harvest or physiological maturity (November to December, 2017). The five quadrats samples from each field were then stored separately in a moisture-free area in preparation for seed cleaning. The samples were hand threshed inside cloth bags in order to reduce soil contamination. The threshed grain samples were then manually cleaned by sifting and winnowing to remove dust, chaff, and other materials.

Soil samples were randomly collected down to a depth of 20 cm from each field site at the time of grain sampling using a 1.9-cm diameter probe and composited. Further, independent undisturbed core soil samples were taken for bulk density determination to help in soil characterization. The collected samples for soil nutrient analysis were air-dried while those for bulk density determination were oven-dried at 110 °C for 24 h at the Adet Agricultural Research Center Soils Laboratory. The soil samples were then ground and sieved through a 2-mm screen before chemical analysis. The soil pH, soil organic carbon (SOC) and cation exchanging capacity (CEC) were determined at the same Laboratory. Total nitrogen (TN) was determined using the Kjeldahl method [42] at Horticoop Soil and Water lab, Bishoftu, Ethiopia. The soil color at each site was determined using the Munsell color chart in dry soil bases. Each sample was analyzed in triplicates for macro and micronutrients (phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), and sodium (Na)) using the Mehlich 3 extraction method (0.2M CH₃COOH, 0.25M NH₄NO₃, 0.015M NH₄F, 0.013M HNO₃, and 0.001M EDTA adjusted to pH 2.5) [43]. The soil samples were analyzed using inductively coupled plasma atomic emission spectroscopy (Spectro CIROS ICP–AES, Spectro Analytical Instruments, Kleve, Germany).

Grain color images were captured using a Tecno-Camon mobile 24 mm pixel camera (Techno Mobile, Hong Kong). The images were first analyzed using RGB (red, green, blue) color detector free software. The RGB color was then converted to HSV (hue, saturation, and value) by RGB to HSV color converter software. The preference for HSV color space was out of the ease of understanding color with the human eyes than other color spaces [44,45]. Ibraheem et al. [45] and Deswal and Sharma [44] described HSV color space as H (hue) measures the purity of a particular color, S (saturation) measures the degree of white color embedded in a specific color and V (value or brightness) detects the intensity of colors. They also noted that V can be used as a luminance which detects what the color brightness is (brightness/lightness or darkness). The value of H is in degree and the S and V values are in percent.

In preparation for nutrient analysis, 100 g of teff grain from each field site sample was ground separately using a RIRIHONG high-speed multifunction rotary grain grinder (Shanghai Yuanwo Industrial and Trade Co. LTD, Shanghai, China). One half (50 g) of the ground sample was used for nutrient analysis [43] at the Horticoop Soil and Water Laboratory, Bishoftu, Ethiopia and the other for composition analysis (crude fiber, fat, crude protein (CP), and starch analysis at the Ethiopian Agricultural Research Institute (Addis Ababa, Ethiopia). Grain proximate and amino acids composition were analyzed using 3 g of homogenized teff flour in duplicate. The flour samples were scanned using a Near Infrared Reflectance Spectrophotometer (NIRS) spinning system (FOSS, Model: NIRS system 5000, Hilleroed, Denmark). Samples were placed in ring cups and their spectra were recorded in reflectance mode in the range from 400 to 2500 nm, at 2 nm intervals as described by Agza et al. [46]. The prediction for the collected spectra was carried out using plant-based and aqua feed calibrations developed by the International Livestock Research Institute in collaboration with Ethiopian Institute of Agricultural Research. As described by Agza et al. [46] the coefficient of determination (R²) for the calibration and validation ranged between 0.93-0.99 and 0.93–0.98 with corresponding standard error values ranging between 0.03–0.25 and 0.04–0.37. The grain mineral elements determination was carried out using Mehlich 3 extraction method (0.2M CH₃COOH, 0.25M NH₄NO₃, 0.015M NH₄F, 0.013M HNO₃, 0.001M EDTA and adjusted to pH 2.5) [43] and gas chromatography-mass spectrometry.

2.3. Statistical Analysis

Soil physicochemical parameters were not subjected to ANOVA because samples collected were composited for each location thus excluding replications. Therefore, location means for each soil physicochemical parameters were presented based on the triplicate analysis in the laboratory. Analysis of variance was performed to detect differences in grain parameters among the different locations and block (northwestern vs. central highlands) using PROC GLM in SAS software [47]. Location and block mean for grain nutrient and color data were separated using the Fisher’s protected least significant difference at alpha = 0.05. Pearson’s correlation coefficients among soil physicochemical and teff grain parameters were generated using the PROC CORR procedure in the SAS software [47].

3. Results

3.1. Soil Physicochemical Properties

Based on the Munsell color chart, soil color varied across the different sample collection sites in the two main teff growing regions of Ethiopia however, the majority were black colored soils (

Table 2. Soil physicochemical parameters sampled during November 2017 at 24 field sites in the two main teff growing regions of Amhara and Oromia in Ethiopia.

Locations	Soil Texture	Soil Color	Bulk Density (g/cm3)	pH	CEC (meq/100g)	SOC (g/kg)	Soil TN (mg/kg)
Abrja	Clay Loam	Black	1.4	7.6	62.6	5.8	488
Abshem	Clay	Red	1.2	5.3	28.9	23.5	1825
Adet 1	Clay	Red	1.2	5.4	31.2	10.7	966
Adet 2	Clay	Black	1.2	6.6	58.8	13.4	747
Akaki	Clay	Black	1.4	7.8	41.7	4.3	555
Alemtena	Loam	Yellowish Brown	1.4	6.9	34.8	8.0	1682
Arerti 1	Clay	Black	1.3	7.7	31.7	16.3	757
Arerti 2	Clay Loam	Black	1.3	7.7	60.5	12.8	887
Atsedemariam	Clay	Black	1.4	7.0	56.4	8.7	471
Bichena	Clay	Black	1.2	6.4	66.0	12.1	917
Birzakani	Clay	Dark Grayish Brown	1.3	6.3	49.8	27.7	1819
Bishoftu	Clay	Black	1.3	6.8	41.9	8.8	774
Bitiejersalafo	Loam	Black	0.9	7.0	47.9	16.4	644
Demdengay	Clay Loam	Dark Reddish brown	1.4	6.2	60.5	16.2	1185
Fetlokuskuam	Clay	Black	1.2	6.7	48.3	10.9	569
Gejagedanba	Clay	Black	1.3	7.8	30.2	10.4	517
Gumdri	Clay Loam	Reddish brown	1.3	5.3	20.3	25.1	1420
Kosheshila	Clay	Black	1.3	7.9	35.1	11.0	450
Kudmi	Clay	Red	1.3	5.3	12.8	19.3	1263
Motta	Clay	Red	1.3	5.4	31.3	13.8	1225
Simada	Clay	Black	1.3	7.8	61.2	10.0	1435
Wondata	Clay	Black	1.3	6.5	58.7	3.3	681
Yubodegabati	Clay	Black	1.3	7.7	28.1	10.9	506
Zenzelima	Clay	Red	1.3	5.3	28.1	13.3	1333
Average			1.3	6.7	42.8	13.0	963
Minimum			0.9	5.3	12.8	3.3	450
Maximum			1.4	7.9	66.0	27.7	1825
SD †			0.1	1.0	15.3	6.1	444

† SD; Standard deviation.

). Soil pH based on the numerical value did not vary widely, however, six out of the 24 locations were considered slightly acidic (Table 2). The CEC value varied widely among locations and for Abrja, Arerti 2, Bichena, and Simada the values were above 60 but for the Kudmi location, CEC was relatively low (Table 2). Both SOC and TN also varied across locations and the SOC values were considered high at the Birzakani, Gumdri, and Abshem locations relative to Wondata location (Table 2). Total N based on numerical value was highest at Abshem followed by Akaki location and some of the lowest values were obtained at Abrja, Atsedemariam and Kosheshila locations (Table 2).

In this study, the numerical values for mineral concentration varied across locations (

Table 3. Soil extractable mineral concentration sampled during November 2017 at 24 field sites cultivated with the teff variety Quncho in the two main teff cultivation regions of Amhara and Oromia in Ethiopia.

Location	Soil Extractable Nutrient
	P	K	Ca	Mg	S	Fe	Mn	Zn	Cu	Mo	Na
	mg/kg
Abrja	9.2	226.0	8349.0	2845.4	9.0	128.0	103.6	1.3	5.8	0.3	93.4
Abshem	10.0	382.1	1618.2	241.1	23.7	106.5	183.3	1.6	4.5	0.3	13.9
Adet 1	7.9	225.7	2302.1	517.8	21.6	123.8	149.8	1.4	4.8	0.3	12.9
Adet 2	7.8	293.0	6031.8	1302.5	8.2	153.8	106.3	1.4	4.1	0.3	31.1
Akaki	8.6	451.9	10653.9	1259.0	8.6	80.5	122.9	1.8	3.6	0.3	42.4
Alemtena	23.8	850.7	2862.7	414.8	12.9	106.2	279.2	2.8	1.5	0.4	44.2
Arerti 1	14.6	777.6	8694.6	998.0	8.6	85.0	263.5	1.6	4.5	0.3	25.0
Arerti 2	29.7	646.7	8543.6	869.1	9.0	58.7	247.4	1.5	3.9	0.3	23.3
Atsedemariam	8.4	320.3	9073.6	2189.0	7.9	124.1	136.0	0.9	4.7	0.3	33.1
Bichena	11.5	348.9	6966.1	1361.6	11.4	168.3	95.9	1.1	5.1	0.3	34.7
Birzakani	10.3	337.3	3358.9	985.0	9.3	99.6	30.3	1.3	3.3	0.3	16.8
Bishoftu	43.0	540.0	5495.4	1135.2	12.7	157.6	245.8	2.0	3.7	0.3	45.2
Bitiejersalafo	10.8	367.7	7231.1	1737.9	12.3	146.8	112.9	1.4	3.9	0.3	71.9
Demdengay	9.9	102.9	3608.5	1072.3	11.9	102.4	76.1	0.8	4.6	0.3	20.8
Fetlokuskuam	6.9	279.5	6680.8	1343.5	8.0	147.2	129.8	1.0	4.1	0.3	34.5
Gejagedanba	10.6	468.6	11719.1	779.0	8.2	69.4	192.0	1.1	3.2	0.3	21.5
Gumdri	9.3	224.0	1350.3	260.7	20.0	110.0	56.6	0.8	3.6	0.3	11.3
Kosheshila	8.6	358.5	12607.5	821.0	9.1	124.5	237.2	1.2	3.1	0.3	18.8
Kudmi	7.2	70.9	1612.1	379.5	30.1	96.1	188.3	1.1	4.9	0.3	11.8
Motta	8.2	267.4	1850.6	407.8	19.0	164.7	153.7	1.5	4.4	0.3	13.1
Simada	10.3	260.9	11115.0	1073.6	8.6	118.3	150.1	1.1	3.6	0.3	19.7
Wondata	9.4	224.7	5670.1	1468.5	10.2	158.0	141.0	1.9	4.8	0.3	24.6
Yubodegabati	10.8	508.3	8632.0	1118.6	8.3	99.5	110.9	1.2	3.6	0.3	30.8
Zenzelima	8.2	231.4	1297.5	324.3	21.3	74.8	113.4	0.9	2.4	0.3	13.2
Average	12.3	365.2	6138.5	1037.7	12.9	116.8	589.5	1.4	4.0	0.3	29.5
Minimum	6.6	70.9	1297.5	241.1	7.9	69.4	30.3	0.8	1.5	0.3	11.3
Maximum	43.0	850.7	12607.5	2845.4	30.1	168.3	279.2	2.8	5.8	0.4	93.4
† SD	1.9	6.7	106.5	20.2	1.6	1.6	2.8	0.03	0.6	0.5	0.6

† SD; Standard deviation.

). For example, the concentration of soil P ranked highest at the Bishoftu location (43 mg/kg) followed by Arerti 2, Alemtena (almost 24 mg/kg), and Arerti 1 (about 15 mg/kg) respectively, while the numerical values for P concentration at most other locations were relatively close (Table 3). The K concentration values showed wider variations at the different locations relative to P, and K concentration numerical values were greatest at Alemtena followed by Arerti 1, Arerti 2, and Bishoftu locations respectively and the lowest was from Kudmi location (Table 3). The Ca concentration numerical value was greatest at Kosheshila and lowest at Gumdri and Zenzelima locations while for Mg concentration, the numerical value was highest at Abrja and lowest at Abshem and Gumdri locations (Table 3). For S concentration, wide variations also occurred across locations based on numerical value and soil S concentration at Abrja, Adet 2, Akaki, Areti 1, Areti 2, Atsedema, Birzakani, Fetlokus, Gejageda, Kosheshila, Simada, Wondata, and Yubodegabati were among the lowest (Table 3). In relation to the concentration of soil Fe concentration, the greatest numerical value was obtained from soils collected from Bichena and lowest at Arerti 2 location (Table 3). There were also, differences in numerical value for all other soil micronutrient concentrations across the locations used in this study and there were wider variations in Mn, Zn, and Cu compared to the variation among locations for soil Mo concentration (Table 3). The numerical values for soil Na concentration varied across locations and were ranked highest at Abrja field site and lowest at Gumdri and Kudmi locations (Table 3).

3.2. Teff Grain Physical and Chemical Quality

The grain of the teff variety Quncho sampled across the main regions of its cultivation in Ethiopia varied in color (Figure 2). There was a significant effect of location (p < 0.05) on teff grain color indices of hue (H), saturation (S), and brightness (V) in this study (

Table 4. Teff grain HSV (H, hue; S, saturation; V, value) color values and proximate composition (CP, crude protein) concentration for the variety Quncho collected from November (2017) to January (2018) at 24 locations in the two main teff cultivation regions of Amhara and Oromia in Ethiopia.

Location	H	S	V	Fiber
	(°)	(%)	(%)	g/kg
Abrja	36.66 h†	25.64 j	81.05 defg	26.3 h	25.5 lm	111.4 c	554.3 k
Abshem	43.12 bc	59.14 a	64.58 l	33.9 d	33.0 ab	92.6 h	605.2 de
Adet 1	47.84 a	52.43 b	70.0 k	37.3 c	30.0 efg	95.1 g	552.9 k
Adet 2	41.06 cdefg	32.38 fghi	77.90 hi	34.7 d	31.6 bcd	93.6 gh	623.8 ab
Akaki	45.46 ab	36.85 de	78.88 ghi	21.0 j	31.1 cde	88.8 ij	605.7 de
Alemtena	45.99 ab	46.44 c	77.65 i	26.0 h	29.8 efg	86.8 k	628.1 a
Arerti 1	41.28 cdefg	27.95 j	81.31 cdefg	18.5 k	31.7 bcd	87.8 jk	574.2 j
Arerti 2	37.82 gh	28.64 hij	80.33 efgh	25.7 h	28.8 ghi	115.8 b	617.1 bc
Atsedemariam	43.41 bc	28.28 ij	83.66 bc	27.7 g	28.3 hij	104.6 e	589.8 gh
Bichena	38.72 fgh	33.26 defg	82.87 bcd	18.6 k	29.5 fgh	92.4 h	605.5 de
Birzakani	36.54 h	43.45 c	69.67 k	29.5 f	21.0 n	126.2 a	581.0 ij
Bishoftu	43.45 bc	15.87 k	87.19 a	18.3 k	28.1 hijk	103.1 e	615.7 bc
Bitiejersalafo	40.81 cdefg	34.49 def	84.18 b	23.8 i	33.5 a	84.8 l	598.3 efg
Demdengay	42.86 bcd	37.42 d	80.65 defg	25.9 h	24.6 m	113.0 c	560.8 k
Fetlokuskuam	40.95 cdefg	33.58 defg	82.67 bcde	21.3 j	27.2 jk	101.2 f	588.1 ih
Gejagedanba	39.54 defgh	29.72 ghij	80.00 fghi	22.1 j	29.8 efg	93.0 h	591.2 fgh
Gumdri	41.51 cdef	46.86 c	63.92 l	30.6 ef	32.8 ab	88.9 ji	581.7 ij
Simada	40.01 cdefgh	35.63 def	80.00 fghi	25.2 h	31.9 bc	84.9 l	604.0 de
Kosheshila	37.96 fgh	26.81 j	81.83 bcdef	40.7 b	28.6 ghij	103.4 e	599.3 fe
Kudmi	42.65 bcde	58.68 a	64.57 l	18.9 k	28.1 hijk	99.7 f	582.7 hij
Motta	39.19 efgh	52.60 b	75.03 j	31.8 e	30.3 def	92.1 h	601.9 de
Wondata	39.53 defgh	32.89 efgh	80.72 defg	36.7 c	28.0 ijk	90.2 i	609.5 cd
Yubodegabati	38.81 fgh	33.59 defg	79.54 fghi	18.0 k	26.9 kl	93.3 h	599.8 ef
Zenzelima	37.89 gh	32.65 efgh	55.04 m	42.3 a	25.2 1m	107.8 d	621.0 ab
LSD (0.05)	3.6	4.3	2.4	1.3	1.4	1.6	8.6

† Within columns, means followed by same lowercase letters superscripts are not different (p > 0.05).

). Based on the color space classification scheme, grains which showed high V and low S were generally very bright white and those with low V and high S values were generally darker in color based on Deswal and Sharma, [44] color classification. The pureness of the teff grain color represented by the H value was generally higher in the locations Adet 1, Akaki, and Alementa than most other locations (Table 4). In relation to the S values, teff grown in Abshem and Kudmi had the highest values among the different locations and were of a pale white color while the lowest S value was for teff grain collected from the Bishoftu location and the grains were very white (Table 4). Other locations that had teff grain classified as very white based on the S value were Abrja, Arerti 1, Arerti 2, Atsede Mariam, and Kosheshila (Table 4). Teff grain V value was greatest for teff grain collected from the Bishoftu location (brighter color) and lowest for grain sampled from Zenzelima location (darker color) while for all other locations, the values were intermediate (Table 4). Teff grown on red colored soils (Nitisols) had lower V and higher S values while teff grown on the black colored soils (Vertisols) had higher V and lower S values (Table 4). Pertaining to grain color of teff grown in the two main regions (northwestern highlands vs. central highlands) both the S (p = 0.004; SD = 5.3) and V (p = 0.001; SD = 3.7) color value were different. However, the H color value was not different (p = 0.237; data not shown) between the two main teff growing regions in Ethiopia. The greater grain S color value was obtained from teff grown in the northwestern highlands (39%) compared to teff grown in the central highlands (32%) and this indicates that the lower saturated grain color of teff was linked to locations within the central highlands while the higher saturated grain color was from locations within the northwestern highlands. The greater grain V value of 81% was obtained from teff grown in the central highlands compared to the northwestern highlands (75%) and is indicative of whiter grains from the central highlands of Ethiopia. In our study, there were significant negative correlations between grain S value and soil pH, SOC, Ca, Mg, S, and Na (

Table 5. Correlation coefficients among soil physicochemical properties and HSV (H, hue; S, saturation; V, value) grain color value of the teff variety Quncho grown on 24 field sites in the main teff cultivation regions of Amhara and Oromia in Ethiopia during November of 2017.

	H	S	V
Soil Color	−0.287	−0.398	0.634 **
pH	−0.218	−0.690 **‡	0.742 **
SOC †	−0.117	0.499 *	−0.540 **
P	0.164	−0.391	0.302
K	0.16	−0.282	0.337
Ca	−0.241	−0.663 **	0.700 **
Mg	−0.285	−0.599 **	0.645 **
S	0.294	0.789 **	−0.787 **
Na	−0.143	−0.442 *	0.518 *
Cu	−0.058	0.106	0.197
Fe	0.045	−0.074	0.359
Mn	0.288	−0.129	0.24
Mo	0.307	0.092	−0.07
Zn	0.367	0.062	0.207

† SOC, soil organic carbon. *, **, ‡ significant at the 0.05, and 0.01 levels respectively.

). Therefore, the soils in our study with greater pH, SOC, Ca, Mg, and S generally exhibited lower S values and thus very whiter color teff grains were observed. For the V value, there were significant positive correlations with black soil color, pH, Ca, Mg, Na, and a negative association with SOC and S (Table 5).

In addition, there was some significant negative relationships between H color value and grain starch (r = −0.41; p < 0.05), S value and CP (r = −0.44; p < 0.05), V value and fiber concentration (r = −0.48; p < 0.05) but a significant positive association between S value and grain fat (r = 0.44; p < 0.05). The higher V value indicates brighter color and lower V value, darker color teff grain. Only the S value was significantly associated with the amino acids alanine (r = −0.50; p < 0.05), arginine (r = −0.45; p < 0.05), aspartic acid (r = −0.56; P < 0.01), methionine (r = −0.51; p < 0.05), serine (r = −0.46; p < 0.05), threonine (r = −0.48; p < 0.05), tyrosine (r = −0.44; p < 0.05) and valine (r = −0.46; p < 0.05). However, there was no significant correlation (p > 0.05; data not shown) between the grain HSV color space values and grain mineral concentrations in this study. For teff grain, the other qualitative traits evaluated were the proximate composition, amino acid composition, and concentration of the different mineral nutrients (P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Mo, and Na) across the 24 locations in the two main teff growing regions of Ethiopia. For grain proximate composition parameters of fiber, fat, crude protein, and starch, there was a main effect of location (p < 0.05) in this study (Table 4). Grain fiber concentration ranked highest at Zenzelima and lowest at Arerti 1, Bichena, Bitiejersalafo, Kudmi, and Yubodegabati locations (Table 4). While for grain fat concentration, teff grain from Abshem, Bitiejersalafo, and Gumdri locations were ranked among the highest and the lowest grain crude fat concentration was obtained from Birzakani location (Table 4). The grain CP concentration was highest at the Birzakani location and lowest at Simada location (Table 4). Teff grain sampled from the locations Adet 2, Alemtena, and Zenzelima were ranked highest in starch concentration and those collected from Abrja, Adet 1, and Demdengay locations were among the lowest in starch concentration (Table 4). Overall, there was no consistent trend where anyone location ranked highest in all the proximate composition parameters in this study which indicated how variable these proximate composition parameters were in this study. Among the proximate composition parameters, only crude fat was different (p = 0.009; SD = 4.4) between the two main teff growing regions and was greater for teff grown in the northwestern highlands (29.0 g/kg) relative to those grown in the central highlands (23.0 g/kg). The grain CP concentration was positively correlated with SOC, and TN but negatively associated with soil Mg, Fe, and Na (

Table 6. Pearson’s correlation coefficients among soil physicochemical properties, grain proximate parameters, and grain mineral nutrients for the teff variety Quncho grown on 24 field sites in the main teff cultivation regions of Amhara and Oromia states in Ethiopia during November of 2017.

	Proximate Composition				Grain Mineral Concentration
Soil Properties	CP	Fiber	Fat	Starch		P	K	Ca	Mg	S	Fe	Mn	Zn	Cu	B	Mo	Na
pH	−0.02	−0.70 **	0.03	−0.06		0.12	0.15	0.29	0.12	0.18	0.20	−0.06	0.25	0.15	0.41 **	0.13	0.29
SOC†	0.54 **	0.34	−0.47 *	0.33		−0.29	−0.21	−0.26	−0.14	0.07	−0.37	−0.40	−0.08	0.19	−0.03	0.07	−0.05
TN	0.50 *	0.47 *	−0.35	0.18		−0.36	−0.19	−0.31	−0.34	−0.11	−0.34	−0.14	−0.11	0.04	0.01	0.25	−0.09
P	0.27	−0.35	−0.27	0.06		0.01	0.08	−0.01	−0.12	−0.18	0.10	−0.01	−0.16	−0.14	−0.10	0.30	0.30
K	0.46	−0.52 *	−0.30	−0.01		−0.16	−0.13	0.01	−0.31	−0.13	−0.06	−0.03	0.14	−0.10	−0.08	0.281	0.08
Ca	−0.17	−0.64 ***	0.09	−0.04		0.16	0.14	0.32	0.17	0.24	0.29	0.01	0.27	0.20	0.42 *	−0.01	0.23
Mg	−0.43 *	−0.50 *	0.31	−0.26		0.23	0.20	0.31	0.32	0.12	0.34	−0.15	0.06	0.17	0.29	0.33	0.22
S	0.13	0.55 **	−0.08	0.01		−0.23	−0.15	−0.33	−0.23	−0.19	−0.03	0.07	−0.18	−0.01	−0.36	−0.06	−0.17
Fe	−0.53 **	−0.07	0.28	−0.11		0.39	0.27	0.43 *	0.30	0.12	0.14	−0.05	0.16	0.05	−0.09	0.16	0.16
Mn	0.18	−0.33	0.02	−0.11		−0.01	0.07	0.00	−0.19	−0.14	0.18	0.02	0.01	−0.08	−0.17	0.14	0.20
Zn	0.20	−0.27	−0.06	−0.20		−0.11	−0.10	−0.08	−0.33	−0.35	−0.10	0.25	−0.09	−0.36	−0.25	0.34	−0.08
Cu	−0.51 *	0.08	0.49 *	−0.23		0.43 *	0.31	0.07	0.34	0.08	0.33	0.17	−0.10	0.11	−0.11	−0.09	−0.05
Mo	0.30	−0.17	−0.13	−0.01		−0.08	0.01	0.08	−0.09	0.12	−0.18	−0.11	0.30	0.05	0.07	0.41 *	0.07
Na	−0.26	−0.62 **	0.163	−0.28		−0.01	0.02	0.15	0.07	−0.10	0.15	−0.19	−0.07	0.07	0.10	0.38	0.15

† SOC, soil organic carbon; TN, soil total nitrogen. *, **, and ***, significant at the 0.05, 0.01, and 0.001 levels respectively.

). Teff grain crude fiber concentration was positively correlated with TN and S, but negatively correlated with soil pH, K, Ca, Mg, and Na while grain fat concentration was only negatively correlated with SOC and positively associated with Cu (Table 6). However, grain starch had no significant associations with any of the soil physicochemical properties (Table 6). There was a significant effect (p < 0.05) of location on all 18 amino acids analyzed in the teff grain of this study (

Table 7. Amino acids concentration for the teff variety Quncho collected from November (2017) to January (2018) at 24 locations in the two main teff cultivation regions of Amhara and Oromia in Ethiopia.

Location	Ala †	Arg	Asp	Cys	Glu	Gly	His	Ile	Leu	Lys	Met	Phe	Pro	Ser	Thr	Trp	Tyr	Val
	mg/100 g
Abrja	500ij ‡	570i	720fgh	160m	1890hi	290h	219hi	270gh	760j	250def	180hi	450jk	580ij	370hi	270hi	70jk	300klm	370klmn
Abshem	610c	760b	920c	220a	2810a	300fghi	320a	430b	1080b	320bc	210d	640b	770ab	501b	400b	120c	390bc	550b
Adet 1	450n	610fgh	720fgh	170ijk	2110g	340cd	210j	280fgh	710lm	230fgh	180hi	480h	640g	380gh	260i	80hi	330h	380jkl
Adet 2	500i	570i	790e	160klm	1790kl	360bcd	190lm	280gh	750jk	240fgh	190g	460ij	570jk	370hi	250j	80hi	310ijkl	360mn
Akaki	500i	590ghi	740f	190ef	1640m	330defg	200kl	270hi	750jk	210ghi	180hi	430l	600hi	360ij	260ih	80hi	300klm	370j-m
Alemtena	460mn	520j	660jk	175hi	1630m	330def	190n	230lm	690n	200ij	170kl	410m	610h	330kl	230k	70kl	280no	330o
Arerti 1	490jk	610efg	710ghi	202cd	1650m	320efgh	210ij	240jk	760ij	190ji	170lm	430l	650g	350j	270ih	70kl	290lm	360lmn
Arerti 2	590d	740b	990b	194de	2680bc	380ab	270d	430b	990c	340b	220b	610c	710d	500b	370c	120c	400b	510c
Atsede Mariam	550e	620def	820r	177gh	2420d	350bcd	250e	360d	890e	300c	210de	550e	700de	450e	320e	90f	360f	444ef
Bichena	530g	610fgh	740f	202cd	1820jkl	380av	230fg	280fg	790hg	270d	180gh	460ij	680ef	390gh	290g	80h	310ij	390hi
Birzakani	480kl	540j	660k	174hij	1470n	270i	200k	220m	700mn	190ij	160m	390n	560k	330l	240jk	60n	270ef	330o
Bishoftu	680a	820a	1140a	190ef	2710b	360bc	280c	490a	1100ab	340b	240a	670a	640g	550a	420a	140a	420a	580a
Bitiejersalafo	580d	630dce	880d	216a	2460d	370ab	300b	380c	990c	370a	200e	580d	780ab	480c	360c	100e	380d	480d
Demdengay	630b	760b	930c	211ab	2820a	270i	320k	430b	1110a	310c	210c	640b	740c	510b	410ab	130b	390de	560b
Fetlokuskuam	540ef	640cd	820e	206bc	2470d	380ab	280c	350d	930d	320bc	190f	560e	790a	470cd	340d	90g	370ef	450ef
Gejagedanba	510hi	580hi	730fg	185fg	1900h	340cde	230fg	280gh	780hi	270d	180i	4700hi	650g	390g	280gh	70ij	310ijk	380jk
Gumdri	480l	580i	680ijk	166jkl	1770l	280i	210j	260ji	740kl	210ih	170k	430l	590hij	350j	260i	70l	290mn	360n
Simada	480kl	570i	690hij	167i-l	1440n	280i	180mn	230klm	690n	180j	170jk	390n	510l	320l	240jk	60lm	260q	340o
Kosheshila	510h	620def	820e	162klm	2300e	370ab	210j	330e	810g	260de	200de	530f	640g	410f	290fg	90fg	350g	410g
Kudmi	550ef	660c	820e	213ab	2180f	390a	270d	320e	870ef	310c	190g	530f	760bc	440e	330e	90f	350g	440f
Motta	500i	610efg	740f	165klm	1870hij	300ghi	230gh	280gh	750jk	250def	180hi	450k	570k	360ij	280gh	80h	300jkl	390ij
Wondata	460m	570i	730fg	140n	1620m	320efgh	160o	240kl	680n	150k	170k	420l	510l	350jk	230k	60mn	280op	330o
Yubodegabati	550ef	620def	820e	205bc	1840ijk	330defg	240f	290f	860f	250def	180ij	490g	660fg	400f	300f	80h	310i	400gh
Zenzelima	540fg	630def	880d	159lm	2630c	330cd	230gh	390c	940d	270d	210c	580d	680ef	460de	320e	110d	380de	450e
LSD (0.05)	10	30	30	10	60	30	10	10	10	30	10	10	30	20	20	40	10	14

† Ala; alanine; Arg, arginine; Asp, aspartic acid, Cys, cysteine; Glu, glutamic acid; Gly, glycine; His, histidine; Ile, isoleucine; Leu, leucine; Lys, lysine; Met, methionine; Phe, phenylalanine; Pro, proline; Ser, serine; Thr, threonine; Trp, tryptophan; Tyr, tyrosine; Val; valine. ‡ Within columns, means followed by same lowercase letter superscripts are not different (p > 0.05).

).

No one location ranked highest for all the 18 amino acids analyzed in the teff grain collected, however, teff grain collected from the Bishoftu location ranked highest for 12 out of the 18 amino acids evaluated (Table 7). Also, between the two main teff growing regions (northwestern vs. central highlands), none of the amino acids were different (p > 0.05). There was a location effect (p < 0.05) on teff grain minerals concentration in this study (

Table 8. Grain mineral nutrients concentration for the teff variety Quncho collected from November (2017) to January (2018) at 24 locations in the two main teff cultivation regions of Amhara and Oromia in Ethiopia.

Location	Grain Mineral Nutrient
	P	K	Ca	Mg	S	Fe	Mn	Zn	Cu	B	Mo	Na
	mg/100 g
Abrja	317.3g†	458.4f	123.8g*	169.6de	24.6g	96.2a	4.0hi	2.04fgh	0.50efg	0.45de	0.087b	9.9ef
Abshem	315.5g	413.8h	123.8g	146.8hi	27.4ef	8.1g	8.0f	2.33e	0.43ij	0.39defg	0.193a	8.9fgh
Adet 1	319.0g	432.1g	113.9hi	154.7gh	21.3ij	35.2bc	19.4a	2.40e	0.51efg	0.20jk	0.030bcd	9.8ef
Adet 2	370.5b	420.9h	124.3fg	176.6cd	20.5jk	23.2f	6.8f	2.55d	0.39kl	0.38efg	0.047bcd	8.6fgh
Akaki	270.6ij	291.4l	109.2ijk	122.2k	16.7l	22.5f	19.9a	2.04fgh	0.36lm	0.23ijk	0.020d	7.2ij
Alemtena	281.5i	432.0g	129.2efg	134.2j	24.7g	6.3g	3.9hi	2.72c	0.43ij	0.30ghi	0.083bc	11.7cd
Arerti 1	356.6cd	519.0b	114.3hi	166.6e	30.0cd	11.2g	13.8c	2.12fg	0.45hij	0.80b	0.020d	11.0de
Arerti 2	243.1k	289.4l	107.1jk	111.8l	15.4lm	24.4ef	2.3ijk	2.11fg	0.49fgh	0.01m	0.053bcd	9.3fg
Atsede Mariam	343.8ef	461.1ef	154.7b	184.1bc	34.7a	40.2b	4.3h	2.91ab	0.56cd	0.65c	0.083bc	14.7a
Bichena	354.5cde	459.1f	136.4cd	150.8gh	27.0f	11.1g	7.1f	2.33e	0.46hij	0.23ijk	0.027bcd	7.9ghij
Birzakani	225.6l	337.6j	106.3k	124.5k	24.6g	4.9g	2.0jk	1.99gh	0.51efg	0.48d	0.087b	10.0ef
Bishoftu	320.9g	436.9g	130.9de	152.9gh	18.7k	32.8bc	4.6h	1.98gh	0.42jk	0.07lm	0.087b	14.4ab
Bitiejersalafo	238.8k	318.3k	129.9ef	135.5j	24.2gh	10.3g	3.5hij	2.16f	0.54de	0.61c	0.033bcd	12.1cd
Demdengay	364.2bc	487.6c	130.0ef	183.7c	26.9f	7.6g	6.9f	1.94h	0.37lm	0.31ghi	0.030bcd	11.9cd
Fetlokuskuam	395.1a	589.2a	131.6de	194.4a	32.1b	26.4def	1.9jk	2.56d	0.65b	0.28hij	0.030bcd	12.8bc
Gejagedanba	269.1j	412.2hi	100.0l	141.6ij	26.0fg	20.1f	9.8e	2.17f	0.44ij	0.34fgh	0.010d	8.0ghij
Gumdri	297.0h	403.6i	116.8h	176.0cd	30.7bc	8.3g	4.4h	2.73c	0.58c	0.41def	0.037bcd	9.9ef
Simada	300.2h	469.6de	138.4c	157.9fg	32.0b	31.9cde	4.9gh	2.85bc	0.70a	1.26a	0.047bcd	14.7a
Kosheshila	341.2f	432.2g	155.8b	169.9de	31.7bc	7.2g	4.2h	2.55d	0.45hij	0.39efg	0.043bcd	12.4cd
Kudmi	314.9g	472.3d	112.5hij	154.9gh	24.2gh	22.0f	1.6k	2.10f	0.52def	0.20jk	0.013d	11.4cde
Motta	324.5g	418.3h	138.6c	155.8fg	28.9de	24.8ef	11.9d	2.37g	0.42jk	0.15kl	0.037bcd	12.3cd
Wondata	350.7def	457.9f	126.1efg	163.5ef	22.8hi	7.2g	16.0b	2.06fgh	0.34m	0.34fgh	0.027cd	7.4hij
Yubodegabati	396.0a	519.3b	170.9a	192.4ab	36.0a	8.2g	6.7f	3.01a	0.47ghi	0.47de	0.030bcd	12.9bc
Zenzelima	196.6m	220.1m	100.0l	100.3m	14.1m	7.2g	6.5fg	1.60i	0.34m	0.18k	0.017d	6.6j
LSD (0.05)	11.5	9.1	5.8	8.6	1.8	7.7	1.8	0.14	0.04	0.10	0.58	1.62

† Within columns, means followed by same lowercase letters superscripts are not different (p > 0.05).

). Among the macronutrients, grain P concentration was ranked highest for teff grown at Fetlokuskuam and Yubodegabati and lowest at Zenzelima location (Table 8). The grain K concentration followed a similar trend like P and grain Ca concentration was highest at the Yubodegabati location and lowest at Gejagedanba and Zenzelima locations (Table 8). The grain Mg concentration was highest at Fetlokuskuam and Yubodegabati locations and lowest at Zenzelima location while for grain S concentration, highest at Atsedemariam and lowest at Akaki and Zenzelima locations (Table 8). Additionally, the grain Na concentration ranked highest at Atsede Mariam, Bishoftu, and Simada but lowest at Akaki, Bichena, Gejagedanba, Wondata, and Zenzelima while all other locations were intermediate and also varied (Table 8). In relation to the teff grain micronutrients, Fe concentration was greatest at Abrja location and ranked lowest at Abshem, Alemtena, Arerti 1, Bichena, Birzakani, Bitiejersalafo, Demdengay, Gumdri, Kosheshila, Wondata, Yubodegabati, and Zenzelima locations (Table 8). There were differences in all other grain micronutrients concentration with wider variations in micronutrients concentration for B and Cu and the least variation occurred for Mo across locations (Table 8). Between the two main teff growing regions, grain Mg concentration differed (p = 0.011; SD = 12.1) and it was greater for teff grown in the northwestern highlands (160.2 mg/100 g) compared to those grown in the central highlands region (144.5 mg/100 g). There were trends for both grain P (p = 0.07; SD = 25.9) and grain S concentration (p = 0.06; SD = 2.9) difference between the two main teff growing regions. Both grain P (320.7 mg/100 g) and S (26.5 mg/100 g) for teff grown in the northwestern highlands region tended to be greater than those grown in the central highlands regions P (291.1 mg/100 g) and S (23.9 mg/100 g) respectively. For teff grain minerals concentration, the significant correlations that occurred with soil physicochemical parameters were all below the 50% threshold and indicated that other external variables would have played a more significant role in the variation of grain mineral concentration among locations (Table 6)

4. Discussion

The characterization of soil properties helps provide an understanding of the variation in crop production and quality in different agro-ecological zones [48]. While Na is not an essential nutrient element required for plant growth its presence in high concentration in the soil can hinder nutrient uptake, growth, and development of crop plants [49]. The common trend of spatial variation in soil physicochemical properties are generally the result of soil formation factors and variation in agricultural soil management in cultivated areas [50] and this may have been the principal factors responsible for the variation in soil physicochemical properties among the locations evaluated. Our results for teff grain color evaluated across multiple locations in the main teff growing regions of Ethiopia is in confirmation with the results of Wu et al. [51] who reported significant color variation in wheat grain from a single variety cultivated over diverse production conditions. Further, Baye [14] reported that the very white and white teff are grown on the vertisols of the central highlands of Ethiopia which corresponds to our results. The results suggested that there could be a direct relationship between grain nutrient and grain color of teff. Tańska et al. [52] reported that variation in grain color of wheat was reflected by changes in its chemical composition but not the environment which is in partial agreement with the results of our study. In addition, the accumulation of carotenoids and anthocyanins pigments in wheat grain accounted for the large variation in its grain color [52,53,54,55] and may have played a role in the grain color differences for the single variety of teff sampled across multiple locations in our study. Overall, the average of 63.5% of the variation in grain color can be attributed to the variation in the soil physicochemical properties that influenced several parameters that were correlated with grain color in this study (Table 5).

For the proximate composition parameters, the grain crude fiber, crude fat, CP, and starch concentrations were aligned with the range reported in several studies for different varieties of teff across different geographic locations [20,22,32,55]. This result is indicative of how these nutritional parameters are highly variable in space. In this study, the seven out of the 18 amino acids had significant correlations with soil P, while only four out the 18 correlated with Mg, and 10 out of the 18 correlated with Na (

Table 9. Pearson’s correlation coefficients among soil physicochemical properties and grain amino acids for the teff variety Quncho grown on 24 field sites in the main teff cultivation regions of Amhara and Oromia states in Ethiopia during November of 2017.

	Amino Acids
	Ala †	Arg	Asp	Cys	Glu	Gly	His	Ile	Leu	Lys	Met	Phe	Pro	Ser	Thr	Trp	Tyr	Val
Soil color	0.381	0.32	0.32	0.49	0.17	0.445	0.33	0.24	0.30	0.35	0.19	0.26	0.33	0.31	0.32	0.25	0.27	0.29
BD ‡	0.13	0.12	0.17	−0.07	0.20	−0.01	0.08	0.19	0.16	0.10	0.21	0.17	0.06	0.15	0.14	0.20	0.16	0.16
Texture	0.16	0.15	0.10	0.03	0.20	−0.27	0.23	0.18	0.20	0.17	0.13	0.15	0.09	0.14	0.20	0.18	0.13	0.17
pH	0.174	0.13	0.15	0.30	−0.02	0.16	0.05	0.07	0.12	0.05	0.07	0.06	0.09	0.08	0.09	0.11	0.06	0.10
SOC§	−0.12	−0.20	−0.24	−0.01	−0.15	−0.29	0.02	−0.18	−0.11	−0.02	−0.23	−0.18	−0.05	−0.17	−0.10	−0.22	−0.19	−0.16
P	0.47 *	0.49 *	0.57 **	0.12	0.25	0.20	0.18	0.42 *	0.35	0.25	0.47 *	0.35	−0.01	0.39	0.37	0.47 *	0.38	0.41 *
K	−0.073	−0.10	−0.03	0.08	−0.22	0.13	−0.20	−0.14	−0.13	−0.13	−0.10	−0.16	−0.11	−0.14	−0.14	−0.10	−0.11	−0.14
Ca	0.118	0.07	0.10	0.21	−0.02	0.24	0.02	0.04	0.06	0.08	0.07	0.04	0.08	0.06	0.05	0.05	0.04	0.05
Mg	0.416 *	0.34	0.32	0.42 *	0.31	0.10	0.41 *	0.35	0.41 *	0.32	0.27	0.36	0.36	0.38	0.39	0.33	0.32	0.38
S	−0.175	−0.08	−0.13	−0.19	0.01	−0.06	−0.05	−0.08	−0.13	−0.03	−0.08	−0.06	−0.03	−0.07	−0.08	−0.09	−0.04	−0.09
Fe	0.063	0.03	0.07	−0.10	−0.01	0.15	0.01	0.03	−0.01	0.07	0.08	0.03	−0.10	0.03	0.01	0.02	0.02	0.03
Mn	0.017	0.14	0.17	−0.03	0.06	0.39	−0.09	0.08	−0.02	0.05	0.16	0.07	−0.01	0.08	0.02	0.11	0.14	0.05
Zn	−0.182	−0.14	−0.07	−0.19	−0.28	0.04	−0.34	−0.20	−0.25	−0.28	−0.15	−0.24	−0.34	−0.22	−0.25	−0.14	−0.21	−0.21
Cu	0.238	0.37	0.15	0.32	0.22	0.04	0.39	0.20	0.24	0.24	0.10	0.23	0.27	0.24	0.30	0.18	0.20	0.28
Mo	−0.285	−0.31	−0.32	−0.23	−0.24	−0.22	−0.33	−0.26	−0.29	−0.33	−0.20	−0.29	−0.22	−0.32	−0.29	−0.20	−0.27	−0.27
Na	0.46 *	0.36	0.38	0.53 **	0.34	0.15	0.47 *	0.40	0.47 *	0.42 *	0.30	0.40	0.44 *	0.42 *	0.45 *	0.41 *	0.38	0.44 *

† Ala; alanine; Arg, arginine; Asp, aspartic acid, Cys, cysteine; Glu, glutamic acid; Gly, glycine; His, histidine; Ile, isoleucine; Leu, leucine; Lys, lysine; Met, methionine; Phe, phenylalanine; Pro, proline; Ser, serine; Thr, threonine; Trp, tryptophan; Tyr, tyrosine; Val; valine. *, **, significant at the 0.05, and 0.01 levels respectively. ^‡ BD, Bulk density; ^§ SOC, Soil organic carbon.

). However, with the exceptions of aspartic acid and soil P, and cysteine and soil Na, all other significant correlations were below the 50% threshold (Table 9) and indicates that other environmental variables may have played a role in the differences in teff grain amino acids concentration. The amino acids concentration of teff grain in this study were in line with those reported for the same variety of teff in a study by Daba [22]. For teff grain minerals concentration, the significant correlations that occurred with soil physicochemical parameters were all below the 50% threshold and indicated that other external variables would have played a more significant role in the variation of grain mineral concentration among locations (Table 6). In our study, high soil mineral concentration did not necessarily correspond to high grain mineral concentration particularly, the grain micronutrients of Fe and Zn showed no significant correlations with soil physicochemical properties and may be indicative of a dilution effect because of higher grain yield in those nutrient-rich locations similar to the trends reported by Fan et al. [56]. The grain mineral concentration in this study was similar to those reported for both white and red teff [57] but often times lower grain mineral concentration than that of the major cereal crop wheat [58,59]. These variabilities in the grain proximate composition parameters, amino acids, and mineral concentration are generally modified by the unique soil physicochemical characteristics, climatic conditions, and the type of agronomic management practices instituted at the location of crop plants cultivation [58,59,60].

5. Conclusions

Grain color of teff dictates its quality and demand in Ethiopia and was influenced by location for the same variety. In this study, teff grown on the red colored soils of the five locations in Amhara (Abshem, Adet 1, Kudmi, Motta, and Zenzelima), had higher S (saturation) and lower V (brightness) color space values, which indicates the production of pale white grains compared to the whiter grains produced on the black colored soils of several locations in both Amhara and Oromia regional states. The soil properties of pH, soil organic carbon, Ca, Mg, and S were strongly associated with grain S value, however, among those soil variables based on the correlation coefficient, soil S concentration had the strongest relationship with teff grain color S value and a similar trend occurred for grain V (brightness) value. The locations of Abshem, Adet 1, Gumdri, Kudmi, Motta, and Zenzelima with high soil S concentration were all in Amhara state which indicates that these locations produced pale white teff grains and for the lower soil S recorded in the other locations in both Amhara and Oromia regional states produced whiter teff grains based on the significant positive correlation between grain S color space value and soil S concentration. There was no strong association between grain proximate composition parameters (grain fiber, fat, CP, starch) and grain color in this study. The grain amino acid concentration of teff was only associated with grain color S value particularly, for aspartic acid and alanine. Grain crude fiber was strongly associated with soil pH and Ca but not crude fat, crude protein, and starch. Also, in this study, soil physicochemical properties had minimal influence on grain mineral concentration and since those relationships were below the 50% threshold level, it is indicative that other factors had played a more significant role in altering grain mineral nutrient concentration. Soil P, Mg, and Na were the only soil properties associated with grain amino acids concentration but none of these relationships were considered strong and therefore, suggested that other major factors were involved in determining the level of grain amino acid concentration present in teff grain. Based on the results of this study, grain color and nutrient concentration were influenced by location within the two regional states of Amhara and Oromia and this may help dictate management interventions necessary to obtain uniformity in grain color, chemical composition, and market equity for the same variety of teff in these two major teff cultivation regions in Ethiopia.