Soil fertility in Lake Ziway area

Transcription

1 Soil fertility in Lake Ziway area 16 May 2011 Addis Abeba Herman de Putter, Flip van Koesveld and Huib Hengsdijk

2 Irrigation and fertilization in relation to Soil Fertility Lake Ziway Small holders Onion and Tomato How to improve fertilization recommendation? Effect of irrigation on Soil? Sampling of soil can contribute to recommendations

3 Why Soil sampling? To know the current nutrient status and constraints of soils Develop fertilizer advice based on soil nutrient level and crop type Tool for soil fertility management Policy: change of blanket fertilization -> soil fertility (Growth and Transformation Plan)

4 Sampling in 2010 IDE Ethiopia and Horticoop 5 distinctive regions Soil type: Lake sediment (Alluvial soils) 6 fields per region (small holders) Period of sampling in August/September 20 cm top layer 40 soil cores per field Analyses on nutrients Analyses on soil characteristics

5 Sampling regions 1 and 2 Haleku and Golba Abosa 3 4 North Korean scheme 5 1 & 2 North of Meki river

6 Haleku / Golba Scheme Bulbula river (outlet) Loam sandy soil Ash layer Alkaline soil

7 Abosha (Private plots) Bore hole / Lake Ziway Loam- sand soil Coarse pumice layer Alkaline sub soil

8 North Korean irrigation scheme Furrow Lake Ziway (North) Clay soil with variable sub soil Saline Alkaline soils

9 North of Meki river Bore holes Meki River (inlet) Clay soil

10 Results form Parameter Unit Result Optimum value Evaluation Advice Existing in Holland To be developed in Ethiopia?

11 Soil fertility characteristics/parameters N supply Estimated amount of nitrogen in the soil that will become available to the crop in one year Phosphorus Pw: extraction with water -> immediately available to the crop P-Al: extraction with weak acid -> long term stock available to crop Potassium K Figure : potassium available to crop: calculated based on mg/100g soil K 2 O, clay content and organic matter

12 Results Soil characteristics Region ph-kcl EC ms/cm Clay content (%) Org. matter (%) CEC mmol/kg Meki River N Korean Abosa Haleku Golba Mean P < N.S LSD

13 Results Soil nutrients (major elements) Region N Supply Kg/ha Pw mg P 2 O 5 / litre P-Al mg P 2 O 5 / 100g PAE mg P / kg K-HCl mg K 2 O /100g K Figure Advice target Meki River N Korean Abosa Haleku Golba Mean P N.S. N.S <0.001 N.S LSD

14 Results Soil nutrients (other elements) Region Mg mg/kg Na mg/kg C % CaCO 3 % Advice target Meki River N Korean Abosa Haleku Golba Mean p <0.001 N.S. N.S. N.S. LSD

15 Effect of irrigation with Lake Ziway water Irrigation map of 1976 Most sampled soils in this presentation marginal suitable for irrigation due to high alkalinity Water used for irrigation 14,000 m 3 per hectare per year (2 seasons) (1400 mm/yr) Water characteristics CaCO 3 = mg per l water ph = 8.0 TDS = 332 (mg/l at 105 o C)

16 Water characteristics ph CaCO 3 mg/l N mg/l (NO 3 -NH 4 ) K 2 O mg/l P 2 O 5 mg/l Meki River Lake Ziway Adami Tullu Bore hole Source: Ministry of water resources Ethiopian water Technology centre Butajira-Ziway Areas development study. January 2008

17 Soil alkalinity affected by irrigation and fertilizer What is the liming effect of irrigation water? ph-kcl increase = kg Acid binding value per ha (ABV) / (lime factor x 10) ABV of CaCO 3 with irrigation = m3 x 102 mg/l = 1428 kg CaCO 3 /ha annually ABV = 1428 x 0.56 = 800 Lime factor = amount of lime required to increase ph with 0.1 in 10 cm soil layer and depends on organic matter content = 74.6 Increase in ph-kcl (10 cm top layer) = 800 / 746 = 1.1

18 Acidification through: Percolation of rainwater = ph annually Use of Urea or Ammonium Sulphate (AS): With 300 kg/ha nitrogen applied as urea: ABV = -300 With 300 kg/ha nitrogen applied with AS: ABV = - 900

19 Soil ph increase/decrease in Lake Ziway area Urea use: ph increase = 0.49 = (800 (Irri CaCO3) 300 (Ureum)) / (74.6 x 10) = 0.67 = (percolation rain) = 0.49 AS use: ph decrease = 0.31 = (800 (irri CaCO3) 900 (AS)) / (74.6 x 10) = = (percolation rain) =

20 Effect of irrigation on ph (10 cm) and on fertilization ph increase water ph increase Ureum ph increase AS N (kg/ha) K2O (kg/ha) P2O5 (kg/ha) Meki river Lake Ziway Adami Tullu

21 Conclusions Soils rich in potassium. High sodium content -> possible reduced K and Ca uptake? -> Blossom end rot in tomato? Alkaline soils -> reduced uptake of P? Meki river area lower soil ph. Irrigation water high CaCO 3 content -> effect on soil ph! Salinization of soils by irrigation? With irrigation substantial amounts of nutrients can be applied.

22 Considerations for fertilizer advice Crop and nutrient require ment Quality Irrigation water Soil status of nutrients Soil ph / alkalinity Sodium content Final recommen dation on N-P-K

23 Betam Amesseg Nalehu Wageningen UR