Total and nitrogen cycling prokaryotes as influenced by biochemical quality of organic inputs and mineral nitrogen fertilizer

Transcription

1 Total and nitrogen cycling prokaryotes as influenced by biochemical quality of organic inputs and mineral nitrogen fertilizer Esther K. Muema 1, Georg Cadisch 1, Bernard Vanlauwe 2, Carolin Ro hl 1, and Frank Rasche 1 1 Institute of Plant Production and Agroecology in the Tropics and Subtropics, University of Hohenheim, Stuttgart, Germany 2 International Institute of Tropical Agriculture, Nairobi, Kenya European Geosciences Union (EGU) conference in Vienna, Austria 28 th April-2 nd May, /29/2014 1

2 Nutrient mining in agricultural soils of Africa % of farmland in SSA is severely degraded by soil nutrient mining. Africa loses ~ USD $ 4 billion worth of soil nutrients every year. Causes Population pressure Small land sizes < 30 kg ha kg ha -1 > 60 kg ha -1 Shifting cultivation no longer possible, led to continuous cropping on the same piece of land (nutrient mining) 4/29/2014 Source: Henao and Baanante, 2006 Soil fertility depletion 2

3 Potential solution Integrated Soil Fertility Management (ISFM): appropriate fertilizer, organic inputs, improved germplasm, adoption by local farmers. Vanlauwe et al., (2010). Outlook on AGRICULTURE vol 39: /29/2014 3

4 Success of ISFM Success not possible without soil microbial engineers. Influence of quality of organic inputs and combinations with mineral N on other important microbial communities? 4/29/2014 4

5 N-cycle Ammonia oxidizing bacteria & archaea (AOB, AOA) NH 4 AMO NH 2 OH HOA NO 2 - NOR Proteolysis /archaea /archaea 4/29/2014 5

6 Hypotheses & Objective High quality inputs as opposed to low quality ones promote the abundance (16S rrna gene) and influence diversity of total bacteria and archaea as well as ammonia oxidizing bacterial (AOB) and archaeal (AOA) communities. Combination of low quality organic inputs and mineral N promote abundance and influence diversity of microbial communities. To study the effects of the application of different quality organic inputs and their combinations with mineral N on the abundance (qpcr) and diversity (TRFLP) of total bacteria and archaea as well as AOB and AOA after 10 years. 4/29/2014 6

7 Study site (ICRAF GIS, 2007) Altitude: 1380 m a.s.l. Rainfall: 1200 mm p.a. Soil: Humic Nitisol 17% Sand 18% Silt 65% Clay (FAO, 1998; Chivenge et al., 2009). 4/29/2014 7

8 5 m Field layout and design + 0 kg N ha kg N ha -1 6 m 6 m RCBD Organic inputs: 4 Mg C ha -1 yr -1 Inorganic N: 120 kg N ha -1 season -1 Blanket application P & K: 60 kg ha -1 4/29/2014 8

9 Organic inputs characterization Parameters Tithonia diversifolia Calliandra calothyrsus Zea mays (stover) C/N Polyphenol, % Lignin, % Quality High Intermediate high Intermediate low Source: Gentile et al., /29/2014 9

10 Soil sampling and analyses Soil sampling (0-15 cm) in Soil chemical analyses (NH 4+, NO 3-, ph, TC, TN, HWEC and HWEN. Microbial analyses (abundance & diversity) on freeze dried soils using (qpcr) and (TRFLP) techniques respectively. 4/29/

11 Quality of organic inputs and mineral N on total communities(qpcr) CON = Control CC = Calliandra calothyrsus ZM = Zea mays TD = Tithonia diversifolia Application but not quality of organic inputs promoted total bacterial and archaeal communities. Combination of organic inputs with mineral N slightly depressed both the communities. 4/29/

12 Quality of organic inputs and mineral N on AOB & AOA (qpcr) CON = Control CC = Calliandra calothyrsus ZM = Zea mays TD = Tithonia diversifolia AOB abundance was promoted by organic N in high quality TD as opposed to low quality ZM and mineral N in N limiting treatments. Addition but not quality of organic inputs promoted AOA. Combination of organic inputs with mineral N slightly depressed AOA. 4/29/

13 ANOSIM Global R Significance level Treatments Quality of organic inputs and microbial communities (TRFLP) Total bacteria ns R Total archaea ns R AOA * R - N = 0 kg N ha -1 AOB * R CON N vs. TD N CON N vs. CC N CON N vs. ZM N TD N vs. CC N TD N vs. ZM N CC N vs. ZM - N Application and quality of organic inputs altered the community structure of AOB. 4/29/

14 ANOSIM Global R Significant level Treatments Organic inputs and mineral N and communities (TRFLP) Total bacteria ns R - N = 0 kg N ha -1 ; +N = 120 kg N ha -1 Total archaea ** R AOA ns R AOB * R CON N vs. CON + N CC N vs. CC + N ZM N vs. ZM + N TD N vs. TD + N Complete community structure separation of AOB with low quality organic input combined with mineral N. Community structure separation on total archaeal communities. 4/29/

15 Conclusions Quality of inputs and their combination with mineral N influenced abundance and community structure of AOB but not AOA. Niche differentiation between AOB and AOA. AOA are adapted to ammonium from mineralization of organic N. AOB are adapted to N from both the fertilizer and from the mineralization of organic inputs. Input quality and mineral N did not influence total bacteria and total archaea. Soil type effect (clayey soil). Duration of field experiment. 4/29/

16 Recommendations Look at seasonal effects at different growth stages of the test crop. Study the effect of soil type on microbial communities. 4/29/

17 Acknowledgement Thank you! 4/29/