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Evaluation of agro-industrial by-products as nutrient source for plantgrowthWakene Negassa a , Christel Baum b & Peter Leinweber ba Debre Zeit Agricultural Research Center, Soil and Water ResearchProcess, Debre Zeit, Ethiopiab University of Rostock, Rostock, Germany

Available online: 19 Jul 2011

To cite this article: Wakene Negassa, Christel Baum & Peter Leinweber (2012): Evaluation of agro-industrial by-products as nutrient source for plant growth, Archives of Agronomy and Soil Science,58:4, 451-460

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Evaluation of agro-industrial by-products as nutrient source

for plant growth

Wakene Negassaa, Christel Baumb and Peter Leinweberb*

aDebre Zeit Agricultural Research Center, Soil and Water Research Process, Debre Zeit,Ethiopia; bUniversity of Rostock, Rostock, Germany

(Received 21 July 2010; final version received 10 September 2010)

Nutrient leaching from dry (COD) and wet (COW) coffee, sisal (SIS), brewerybarley malt (BEB) and sugar cane (FIC) by-products, and linseed (LIC) and nigerseed cakes (NIC), and uptake by maize were studied in a pot experiment withtropical Alfisol. After three months, soils were leached to recover labile plantnutrients, and root and shoot biomass was harvested. The leachate from FIC-amended soil had the highest concentration of inorganic P (0.90 mmol L71),whereas the highest concentrations of potassium (K) (48,088 mmol L71) andcalcium (2566 mmol L71) were determined in leachates from COD and BEBtreatments, respectively. The amendments significantly increased K uptake bymaize proportional to the amount of K applied, but the effects for other plantnutrients were small. The results indicated that pre-decomposition of agro-industrial by-products may increase the nutrient release in tropical soils.

Keywords: nutrient uptake; nutrient leaching; phosphorus; tropical soil; maize

Introduction

Beside nitrogen, phosphorus (P) is the second most frequently limiting macronu-trient for plant growth (Schachtman et al. 1998). P limitation of plant growth andmicrobial nutrient turnover is particularly severe in developing countries. Most ofthese countries are situated in subtropical and tropical climates where P fixation andlow P input hamper crop production (Singh and Lal 2005). Organic residues canimprove both short-term nutrient availability and long-term maintenance of soilorganic matter (SOM) levels in tropical agriculture (Palm et al. 1997, 2001).Furthermore, organic compounds released during the decomposition of organicresidues can block P sorption in strongly weathered tropical soils (Negassa et al.2008). However, nutrient-rich wastes such as agro-industrial by-products and urbanwastes have received little attention in research and application for soil amendmentin developing countries.

The potential of many locally available organic materials for soil amendment intropical agroecosystems has been summarized by Palm et al. (1997, 2001). Most ofthe previous studies in subtropical and tropical agroecosystems surveyed the qualityof organic materials for soil amendment with the emphasis on nitrogen (N) (e.g.Shepherd et al. 2003, 2005; Vanlauwe et al. 2005). Although the value of organic

*Corresponding author. Email: peter.leinweber@uni-rostock.de

Archives of Agronomy and Soil Science

Vol. 58, No. 4, April 2012, 451–460

ISSN 0365-0340 print/ISSN 1476-3567 online

� 2012 Taylor & Francis

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resources for soil amendment has been generally accepted for centuries (Bundy et al.2005), little information is available on their supply capacity for plant nutrients otherthan N. Therefore, the objective of this study was to evaluate the nutrient supplycapacity of important agro-industrial by-products from Ethiopia for maize growthon a tropical Alfisol under greenhouse conditions.

Materials and methods

Soil and agro-industrial by-products sampling

A composite arable soil sample was collected at a village called Fayyinera nearbyNekemte city, western Ethiopia. The sampling site is located at about 98 050 N,368 60 E) and an altitude of 1950 m. Annual rainfall was 2089 mm. Minimum andmaximum temperatures were 12 and 248C, respectively. The soil type at the samplingsite was an Alfisol with the following physicochemical properties at the upper 10 cm:71% clay, 24% silt, 5% sand, 3.69% total C, 0.33% total N and 0.04% total S. Theconcentrations of exchangeable cations were (cmolc kg71 soil) 0.93 Kþ, 0.83 Ca2þ,0.38 Mg2þ, 0.02 Naþ, 1.24 Al3þ and 0.25 Hþ. The soil sample pH in H2O and KCl,determined at 1 : 2.5 (wt/v) soil-to-solution ratio, were 4.5 and 3.8, respectively, andtotal concentrations of selected elements were (g kg71) 1.2 P, 11.10 K, 0.79 Ca, 3.40Mg, 89.94 Fe, 1.72 Mn, 102.38 Al, 0.08 Zn, 0.05 Cu, and 0.008 B.

The agro-industrial by-products used in this study were collected from differentparts of Ethiopia. These were dry processed (COD) and wet processed (COW) coffee(Coffea arabica L.) by-products, barley (Hordeum vulgare L.) malt residue frombrewery (BEB), sisal [Agave sisalana (Hanf)] factory by-products (SIS), filter cake ofsugar cane (Saccharum officinarum L.) processing (FIC), linseed (Linum usitatissimusL.) cake (LIC) and nigerseed [Guizotia abyssinica (L.f.) Cass] cake (NIC) from foodoil processing. The pH and concentrations of C and selected essential elements in theagro-industrial by-products have been published elsewhere (Negassa et al. 2010a).

Experimental set-up

A pot experiment was designed with the following treatments: control (withoutamendment), recommended mineral fertilizer-P (20 kg ha71) and seven agro-industrial by-products at the rate of 40 kg P ha71. The agro-industrial by-productswere applied without decomposition because sequential P fractionation of the agro-industrial by-products revealed that 450% of the total P was in the labile form(Negassa et al. 2010b). The amounts of essential elements applied with the agro-industrial by-products are presented in Table 1. Mineral P and the seven agro-industrial by-products were manually mixed with 100 g soils and filled into‘CombiSart’ pots (volume 250 mL, described in Schlichting and Leinweber 2009)with three replications and irrigated to 60% field capacity for a week before planting.Three maize seeds per pot were planted and thinned to two plants after two weeks.The maize plants were allowed to grow in a greenhouse with 26/168C day/nighttemperature, 52% relative humidity by watering regularly and a daily 16 hphotoperiod for three months. About 92 kg nitrogen (N) ha71 in the form ofammonium nitrate was applied in three splits to prevent nitrogen deficiency.

After three months of maize growth, one replication was leached to determine theconcentrations of P, K, calcium (Ca), magnesium (Mg) and iron (Fe) released duringdecomposition of the organic by-products in soil, but not taken up by maize plants.

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Leaching was accomplished by application of 200 mL of double-distilled water andleachate was collected with a suction pump and filtered through 0.45 mm membranefilters. The concentration of inorganic phosphorus (Pi) in the leachates was determinedby spectrometry using the malachite green method (Ohno and Zibilske 1991), whereasthe concentrations of total P, K, Ca, Mg and Fe were determined with inductivelycoupled optical emission spectrometry (ICP-OES; JY 238 UL Trace, France).

Maize shoot and root biomass was harvested, and root biomass was thoroughlyseparated from soils and washed with water on sieves soon after leaching, and thenchopped and dried in an oven at 308C for five days. Shoot and root biomasses werecombined and ground at 0.5 mm size for determination of N, P, K, Ca, Mg and Feconcentrations in maize tissue.

The concentration of N in maize tissues was determined by CNS analyser (VarioEL III; Elementar Analysensysteme, Hanau, Germany). Potassium, Ca, Mg and Fewere measured after microwave-assisted digestion in concentrated nitric acid and30% hydrogen peroxide [United States Environmental Protection Agency (US EPA)1996] with ICP-OES.

Data analysis

The software package SPSS 13.0 was used for one-way analysis of variance andsimple linear correlation and regression functions after testing for the normality ofthe data. The LSD values were calculated for the significantly different values at 5%probability level for mean separations.

Results and discussion

Concentrations of selected elements in leachates

The highest concentration of Pi was determined in leachates from soil amended withFIC (Table 2). However, the concentrations of Pi in the leachates of this study were

Table 1. Selected total elements concentrations applied with the agro-industrial by-productsand maize seeds to the soil sample.

P N K Ca Mg Na Fe

(mmol kg71 soil )

Maize seed 0.52 5.71 0.44 0.10 0.12 ND NDAgro-industrial by-products

Control 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00Mineral-P 0.00 0.52 0.00 0.00 0.00 0.00 0.00 0.00COD 30.0 1.07 29.13 22.30 2.89 13.62 0.30 0.14COW 16.2 1.07 35.55 8.26 3.59 1.15 0.26 0.21SIS 12.6 1.07 7.57 5.52 16.34 2.96 1.74 0.02BEB 9.2 1.07 22.70 0.08 0.47 0.58 0.13 0.05FIC 3.6 1.07 1.64 0.64 2.40 0.45 0.04 1.25LIC 3.3 1.07 10.14 0.59 2.25 0.41 0.04 1.15NIC 2.7 1.07 9.28 1.00 0.40 0.53 0.04 0.11

Note: ND, not determined; AIBP, agro-industrial by-products; control, without amendment; Mineral-P,recommended fertilizer-P; COD, dry processed coffee by-products; COW, wet processed coffee by-products; SIS, sisal by-products; BEB, barley malt residues from brewery; FIC, filter cake from sugarindustries; LIC and NIC, linseed and niger seed cakes from food oil processing.

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lower than the average Pi concentrations in leachates from sand, clayey loam andsilty loam of temperate soils (Turner and Haygarth 2000). To the best of ourknowledge, no P leaching study has been conducted on tropical soils. Other studiesin soils of temperate agro-ecosystems with and without organic amendmentsrecovered higher concentrations of organic P (Po) than Pi (e.g Chardon et al. 1997;Toor et al. 2003). These authors stressed that Po was more mobile than Pi because ofthe high reactivity of Pi ions with pedogenic oxides in soil. This may be also thereason for low concentration of Pi in leachates from the soil under study, whichhad high concentrations of Al, Fe and Ca. Because the total phosphorus (Pt)concentration in the leachates was the same as Pi, the concentration of Po (Pt – Pi)was 0 or below the detection limit in the leachates of this study. This is explained bythe passage of only soluble reactive P through the 50.45 mm filter membrane (Pantand Reddy 2001).

The concentrations of K, Ca, Mg, Fe and Al in the leachates from differenttreatments were highly variable (Table 2). The highest concentration of K wasdetermined in leachates from COD, Ca from BEB and Mg from SIS amendments.However, only the concentration of K applied with the by-products was positivelyand significantly correlated (r ¼ 0.96, p ¼ 0.01) with the leachate K concentration.The concentrations of these elements in the leachates of the control treatment wereeither equal to or greater than in the leachates of amended treatments. Usually, thepresence of plants can increase the turnover of both applied and native organicmatter. Previous studies also showed that SOM decomposition greatly increased inthe presence of plants when compared with soil incubation without plants (Chenget al. 2003; Dijkstra et al. 2009). Therefore, we suspect that our results were plantspecific and might vary for other plant species and on soil without vegetation.

Maize biomass and uptake of selected elements

The root and shoot biomass, and height of maize were not significantly different(p 4 0.05) among the treatments (data not shown). The root biomass of maize wasstrongly correlated with shoot biomass where the shoot biomass explained 70% of

Table 2. Concentration of selected elements in leachates of a tropical soil amended withagro-industrial by-products.

P K Ca Mg Fe

(mmol L71)

Control 0.42 8684 1368 5042 0.82Mineral-P 0.32 6965 1545 4501 0.63COD 0.45 48088 1328 6503 0.70COW 0.45 22675 1100 4702 0.70SIS 0.23 5542 2242 7238 0.57BEB 0.29 3757 2566 7012 0.48FIC 0.90 3381 2291 5642 0.36LIC 0.29 4679 1557 5287 0.57NIC 0.84 9177 1767 7445 0.38

Note: Mineral-P, recommended fertilizer-P; COD, dry processed coffee by-products; COW, wet processedcoffee by-products; SIS, sisal by-products; BEB, barley malt residues from brewery; FIC, filter cake fromsugar industries; LIC and NIC, linseed and niger seed cakes from food oil processing.

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the variance in root biomass (Figure 1). Phosphorus deficiency favoured the growthof roots over shoots, regardless of growth stage (Hansen and Lynch 1998; Nielsenet al. 2001). This showed that P was most likely not the limiting element for maizegrowth in the soil sample used in this study. Furthermore, root-to-shoot ratios couldalso be affected by the total size of plants rather than by soil P availability (Rubio2009). For example, the root-to-shoot ratio of small plants, because they are youngor they are under the influence of any growth-limiting factor, is greater that of olderor non-stressed plants. N, P, K, Ca and Mg uptake by maize were significantlydifferent (p 5 0.05) among some treatments, but insignificant for Fe in alltreatments (Table 3). N uptake by maize was not significantly different amongmost of the treatments in which the highest N uptake was observed in controltreatment. Although an equal amount of mineral fertilizer-N was applied to alltreatments, including control, the amount N applied with the agro-industrial by-products had a wide range (2–36 mmol N kg71 soil). However, these organic-Nvariations had low effects on the maize growth. This could be attributed to the factthat high amounts of mineral fertilizer-N can hinder organic-N mineralization(McCarty et al. 1992; Dilly and Nannipieri 2001).

Similarly, the highest P uptake by maize after the application of NIC was notsignificantly different (p 4 0.05) from the control treatment. This also clearlyindicates the low contribution of the P applied with the agro-industrial by-productsto maize growth because there was sufficient labile native P in the soil sample.Furthermore, surprisingly, the P concentration in the maize seeds used for plantingwas equal to the recommended fertilizer-P rate for cereal production in soils oftropical agroecosystems (see Table 1) (Quinones et al. 1997). Previously, Frossardet al. (1996) and Sharma and Prasad (2002) reported a lack of any significantdifferences in the P uptake by crops from a clayey soil rich in Fe oxides, and loamysoils rich in available P, which were amended by decomposed sludge and theincorporation of crop residues. According to these authors, the Fe oxides sorbed theP released from sludge, whereas the high available soil P masked the uptake of sludge

Figure 1. Relation of root and shoot biomass of maize grown on a tropical soil amendedwith agro-industrial by-products.

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P by ryegrass (Lolium perenne L). Similarly, Toor (2009) also indicated that thebeneficial effects of poultry manure on the P supply of plants were limited toP-deficient soils. Furthermore, application of undecomposed poultry manureprovided lower maize yields than an equivalent amount of mineral fertilizer-P(Materechera and Morutse 2009). The application of manure, which was rich inlabile P, caused increased transformation into more stable P fractions (Waldrip-Dailet al. 2009). These previous studies clearly indicated that high soil P concentrations,other soil properties, the decomposition stage of the applied organic amendment andP transformations can significantly affect the availability of P derived from organicwastes.

The application of agro-industrial by-products significantly (p 5 0.05) increasedK uptake by maize (Table 3). The highest K uptake by maize was observed withCOD amendment, whereas the lowest K was recorded in control and mineralfertilizer-P. Incorporation of wheat and rice residues also resulted in a 90% uptakeof total K by rice and wheat crops (Sharma and Prasad 2002). The highest K uptakeby maize with the application of agro-industrial by-products in this study, and fromcrop residues elsewhere, was attributed to the fact that K is not a structuralcomponent of plant materials that can be easily mineralized when incorporated intosoils (Mengel 2007). In contrast to K uptake, Ca uptake by maize did not follow thetrend in Ca concentrations in the agro-industrial by-products. For example, theconcentration of Ca in BEB was the lowest among the samples, but BEB amendmentresulted in the second highest Ca uptake by maize (Table 3). This may indicate thatthe availability of Ca from agro-industrial by-products depended on the decom-position rate of the by-product in the soil. This hypothesis was supported by thehighest Ca concentration in the leachate and maize Ca uptake with BEB amendment,despite the lowest Ca concentrations being applied with BEB compared with theother samples (see Tables 1–3). Furthermore, a pervious incubation study also

Table 3. Concentrations of selected elements in maize tissues grown in soil sample mendedwith agro-industrial by-products.

N P K Ca Mg Fe

(103 mmol kg71 DMa)

Control 2078.a 31.abc 491.e 133.abcd 98.abc 13Mineral-P 1999.bc 32.ab 505.e 124.bcde 90.c 17COD 1606.e 25.d 882.a 86.e 64.d 10COW 1892.d 23.d 733.b 108.de 73.d 12SIS 1949.cd 25.d 696.bc 150.abc 91.bc 24BEB 2099.a 29.bcd 608.cd 163.ab 98.abc 14FIC 2099.a 27.bcd 561.de 164.a 94.abc 17LIC 2063.ab 28.cd 583.de 122.cde 101.ab 11NIC 2063.ab 36.a 686.bc 91.e 104.a 8LSD (5%) 0.07 5.62 98.11 38.90 10.24 NSCV% 1.7 11.5 8.9 17.7 6.54 50.23

Note: Mineral-P, recommended fertilizer-P; COD, dry processed coffee by-products; COW, wet processedcoffee by-products; SIS, sisal by-products; BEB, barley malt residues from brewery; FIC, filter cake fromsugar industries; LIC and NIC, linseed and niger seed cakes from food oil processing. DMa, maize drymatter, Control, without any amendment. Numbers followed by the same letters within a column are notstatistically significant at p 5 0.05. NS, not significant.

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showed that BEB was an easily mineralized by-product, which caused the highestrate and cumulative amount of soil respiration (Negassa et al. 2010a). The slowrelease of Ca from most of the agro-industrial by-products was attributed to thefunction of Ca as a structural component of plant materials, in particular, Cabridging phosphate carboxylate groups of phospholipids and proteins at membranesurfaces (Legge et al. 1982). Moreover, Ca is a key element in the structure ofprimary cell walls (Willats et al. 2001; Blamey 2003).

Similar to the Ca uptake, the Mg uptake of maize was not associated with theamount of Mg applied with the agro-industrial by-products. For example, Mguptake was lower with COD amendments regardless of the high concentration of Mgapplied with COD (13.62 mmol kg71 soil) compared with Mg applied with BEB(0.58 mmol kg71 soil) (see Table 1). However, the highest Mg uptake by maize wasobserved with BEB amendment. Tian et al. (1992) also reported significantvariations among the leaves of different plant species in releasing Mg duringincubation. This clearly indicates that both the amount of nutrients applied with theby-products, and also the decomposition rate of the by-products may significantlycontribute to short-term effects on plant nutrition. Furthermore, Mg is a structuralcomponent of plant materials, which is slowly mineralized in soil compared with K(Merhaut 2007). The Fe uptake of maize was not significantly different (p 4 0.05)among the different treatments, although some agro-industrial by-products like LICand FIC had high Fe concentrations.

Pearson’s correlation analysis revealed that the concentrations of essentialelements applied with the agro-industrial by-products were not significantlycorrelated with their respective uptakes by maize (Table 4). However, theconcentration of applied K with the by-products was strongly and positivelycorrelated (r ¼ 0.94, p ¼ 0.01) with the uptake of K by maize. Furthermore, the Kapplication was strongly and negatively correlated with the uptake of Mg by maize(r ¼ 70.92, p ¼ 0.01). The concentration of Mg applied with the agro-industrialby-products was 2–11 times less than the amount of K applied, nevertheless Mguptake was strongly and positively correlated (r ¼ 0.84, p ¼ 0.05) with the Kuptake by maize (Table 4). Ohno and Grunes (1985) also reported that highconcentrations of K inhibited Mg uptake by plants, but the Mg concentration in thenutrient solution did not affect K uptake. The antagonistic effects of highconcentrations of K on Mg uptake of plants were also summarized in detail byMerhaut (2007).

Table 4. Pearson correlation coefficient between nutrients applied with agro-industrial by-products and uptakes by maize plants. Numbers of paired means were seven.

Applied(mmol kg71 soil)

Uptake (mmol kg71 DM)

K Ca Mg Fe

N 0.55 70.70 70.75 70.52K 0.94** 70.60 70.92** 70.20Ca 0.18 0.27 70.08 0.78*Mg 0.84* 70.52 70.78* 70.15Fe 70.61 0.24 0.30 0.06Al 70.59 0.20 0.33 0.02

Note: Correlations are significant at the 0.01 (**) and 0.05 (*) probability levels.

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Conclusions

Application of agro-industrial by-products can improve the nutrient supply toplants, but only for K we found a direct correlation between the concentration in theby-products and uptake by maize plants. Releasing structurally bound essentialelements such as N, P and Ca in the agro-industrial by-products by decompositionbefore incorporation into soils appears to be required for immediate benefits to plantgrowth. Furthermore, soils with P deficiency and crops tolerant to acid soils shouldbe used to evaluate the potential of the agro-industrial by-products as sources ofnutrients for plant growth in subsequent investigations. The indication of element-specific controls of the nutrient release after application of the agro-industrial by-products in P fixing tropical soils is a lasting challenge for future investigations.

Acknowledgements

The German Academic Exchange Service (DAAD) provided a fellowship for W. Negassa.We are grateful to Dr A. Schlichting, and Mrs M. Hopp, Institute for Land Use, Universityof Rostock, for their technical support during experimental set up and laboratory analyses.We also acknowledge two anonymous reviewers for their constructive comments andsuggestions.

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