Nitrogen fertilizer equivalencies of organics of differing quality and optimum combination with inorganic nitrogen source in Central Kenya

Kimetu, J.M.; Mugendi, Daniel N.; Palm, Cheryl; Mutuo, Patrick K.; Gachengo, Catherine N.; Bationo, A.; Nandwa, S.M.; Kung’u, J.B.

doi:10.1023/b:fres.0000019043.33580.a6

Cited by 56 publications

(55 citation statements)

References 15 publications

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“…Such chronosequences substitute time for space and have to be carefully selected to assure similar properties along the time series (Huggett 1998). Climate varied only slightly between the sites (Kimetu et al 2008). Farms of different time since conversion were in close proximity, from 100 m to a few kilometres, with often similar distances between farms of the same time since conversion (see accessory publication on journal's website).…”

Section: Study Sitementioning

confidence: 99%

“…The pre-existing SOC content in this soil sequence ranges from 85 to 21 mg C/g, with total N between 7.0 and 1.8 mg N/g and microbial biomass decreasing from 4.8 to 0.9 mg C/kg with increasing age of conversion (Table 1). A more detailed description of these sites can be found in Kimetu et al (2008), Kinyangi (2008), and Ngoze et al (2008).…”

Section: Study Sitementioning

confidence: 99%

“…Due to its long half-life (Baldock and Smernik 2002), biochar could be one of the best approaches to sequester C in soils, contributing to a net carbon dioxide withdrawal from the atmosphere (Lehmann 2007;Laird et al 2009). In addition to improving nutrient retention ability (Glaser et al 2002;Bélanger et al 2004;Major et al 2009), water-holding capacity (Glaser et al 2002), and microbial functions of soils (Thies and Rillig 2009), substantial increases in soil organic carbon (SOC) have been shown with the application of biochar in highly SOC-depleted soils (Kimetu et al 2008;Novak et al 2010). Biochar can thus be a valuable tool in enhancing fertility and C stocks in soils that are highly depleted of SOC.…”

Section: Introductionmentioning

confidence: 99%

“…In the recently developed C saturation concept, Six et al (2002), Stewart et al (2007Stewart et al ( , 2008, and Gulde et al (2008) indicate that the physicochemical characteristics of soils put a ceiling on the protective capacity of SOC pools by soil aggregates and clay minerals, which limits increases in SOC even with the addition of organic inputs (e.g. Campbell et al 1991;Paustian et al 1997;Solberg et al 1997;Kimetu et al 2008). Six et al (2002) and Stewart et al (2007) suggested that soils with high OC status have a lower C stabilisation efficiency than soils of low OC status.…”

Section: Introductionmentioning

confidence: 99%

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Stability and stabilisation of biochar and green manure in soil with different organic carbon contents

2010

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Abstract. Due to its recalcitrance against microbial degradation, biochar is very stable in soil compared to other organic matter additions, making its application to soils a suitable approach for the build-up of soil organic carbon (SOC). The net effects of such biochar addition also depend on its interactions with existing organic matter in soils. A study was established to investigate how the status of pre-existing soil organic matter influences biochar stabilisation in soil in comparison to labile organic additions. Carbon loss was greater in the C-rich sites (C content 58.0 g C/kg) than C-poor soils (C content 21.0-24.0 g C/kg), regardless of the quality of the applied organic resource. Biochar-applied, C-rich soil showed greater C losses, by >0.5 kg/m 2 .year, than biochar-applied C-poor soil, whereas the difference was only 0.1 kg/m 2 .year with Tithonia diversifolia green manure. Biochar application reduced the rate of CO 2 -C loss by 27%, and T. diversifolia increased CO 2 -C losses by 22% in the C-poor soils. With biochar application, a greater proportion of C (6.8 times) was found in the intraaggregate fraction per unit C respired than with green manure, indicating a more efficient stabilisation in addition to the chemical recalcitrance of biochar. In SOC-poor soils, biochar application enriched aromatic-C, carboxyl-C, and traces of ketones and esters mainly in unprotected organic matter and within aggregates, as determined by Fourier-transform infrared spectroscopy. In contrast, additions of T. diversifolia biomass enriched conjugated carbonyl-C such as ketones and quinones, as well as CH deformations of aliphatic-C mainly in the intra-aggregate fraction. The data indicate that not only the stability but also the stabilisation of biochar exceeds that of a labile organic matter addition such as green manure.

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Section: Study Sitementioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Stability and stabilisation of biochar and green manure in soil with different organic carbon contents

2010

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“…The maize variety planted was hybrid 512. The experiment, which was designed and established by TSBF in 1999, consisted of 10 treatments replicated four times (Kimetu et al 2004). The treatments sampled for N 2 O, N leaching and N recovery were tithonia treatment, urea treatment and the control.…”

Section: Site Descriptionmentioning

confidence: 99%

Partial balance of nitrogen in a maize cropping system in humic nitisol of Central Kenya

Kimetu

Mugendi

Bationo

et al. 2006

Nutr Cycl Agroecosyst

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The application of nitrogen in a soil under agricultural production is subject to several pathways including de-nitrification, leaching and recovery by an annual crop. This is as well greatly influenced by the management practices, nitrogen source and soil conditions. The main objective of this study was to investigate the loss of nitrogen (N) through nitrous oxide (N 2 O) emissions and mineral N leaching and uptake by annual crop as influenced by the N source. The study was carried out at Kabete in Central Kenya. Measurements were taken during the second season after two seasons of repeated application of N as urea and Tithonia diversifolia (tithonia) leaves. Results obtained indicated that nitrous oxide (N 2 O) emissions at 4 weeks after planting were as high as 12.3 lg N m À2 h À1 for tithonia treatment and 2.9 lg N m À2 h À1 for urea treatment. Tithonia green biomass treatment was found to emit N 2 O at relatively higher rate compared to urea treatment. This was only evident during the fourth week after treatment application.Soil mineral N content at the end of the season increased down the profile. This was evident in the three treatments (urea, tithonia and control) investigated in the study. Urea treatment exhibited significantly higher mineral N content down the soil profile (9% of the applied N) compared to tithonia (0.6% of the applied N). This was attributed to the washing down of the nitrate-N from the topsoil accumulating in the lower layers of the soil profile. However, there was no significant difference in N content down the soil profile between tithonia treatment and the control. It could be concluded that there was no nitrate leaching in the tithonia treatment. Nitrogen recovery by the maize crop was higher in the urea treatment (76% of the applied N) as compared to tithonia treatment (55.5% of the applied N). This was also true for the residual mineral N in the soil at the end of the season which was about 7.8% of the applied N in the urea treatment and 5.2% in the tithonia treatment.From this study, it was therefore evident that although there is relatively lower N recovery by maize supplied with tithonia green biomass compared to maize supplied with urea, more nitrogen is being lost (through leaching) from the soil-plant system in the urea applied plots than in tithonia applied plots. However, a greater percentage (37.8%) of the tithonia-applied N could not be

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Effects of organic and mineral sources of nutrients on maize yields in three districts of central Kenya

Kimani

Esilaba

Odera

et al.

Advances in Integrated Soil Fertility Management in Sub-Saharan Africa: Challenges and Opportunities

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Nitrogen fertilizer equivalencies of organics of differing quality and optimum combination with inorganic nitrogen source in Central Kenya

Cited by 56 publications

References 15 publications

Stability and stabilisation of biochar and green manure in soil with different organic carbon contents

Stability and stabilisation of biochar and green manure in soil with different organic carbon contents

Partial balance of nitrogen in a maize cropping system in humic nitisol of Central Kenya

Effects of organic and mineral sources of nutrients on maize yields in three districts of central Kenya

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