Phosphorus Use Efficiency for Cucumber (Cucumis Satnus L.) Grown on Acid Soils
Hilman, Yusdar (2003) Phosphorus Use Efficiency for Cucumber (Cucumis Satnus L.) Grown on Acid Soils. PhD thesis, Universiti Putra Malaysia.
Phosphorus (P) use efficiency for cucumber grown on acid soils was studied. The objectives of this experiment were: (i) to screen the solubility of three phosphate rocks in acid soils with the aim of selecting one phosphate rock (PR) with the best P and calcium (Ca) solubility in acid soils - a laboratory study, (ii) to determine the most economical P source, critical P level, and the relationship between P uptake (Ps) and phosphorus dissolution from PR (PDP) or Pb/P - green house study, and (iii) to improve upon P availability in an acid soil cultivated with cucumber influenced by mycorrhiza (VAM) inoculation, organic matter (OM) amendment and P rate - field study. Results of the experiment indicated that in a closed incubation system, dissolution of Indonesian phosphate rock (IPR) (30.20 to 100.00%) was the highest followed by Gafsa phosphate rock (GPR) (17.00 to 68.80%) and then China phosphate rock (CPR) (19.80 to 53.80%). Three major factors which may affect the PR dissolution were identified: (i) soil texture (STF), (ii) soil acidity (SAF) and (iii) fertilizer (FF). Soil texture (clay, silt and sand contents) and P retention capacity showed the highest magnitude (54%) of the factor effect on P dissolution. In a green house, there was significant difference between soils and P levels with regards to total plant dry matter yield (DMY), leaf area, soil N, K and Ca nutrients, and N, K and Ca uptake by cucumber at three harvests extending from 14 to 42 days. The IPR (RAE = 177.10%) and GPR (RAE = 145.50%) were superior to triple superphosphate (TSP). On the soils with high P retention capacity (> 50%), the supply of P from both IPR and GPR on cucumber were much cost effective than TSP, with relative economic effectiveness (REE) values of 495.50% and 318.60% for IPR and GPR, respectively. For GPR, there was a positive correlation between P uptake (L\Ps) and P dissolution (L\P) as well as P uptake (L\Ps), and P availability (L\Pb). Similar observation was made for IPR and not TSP. There was a close relationship between residual P determined by Pb method and P uptake (Ps) by cucumber at 28 and 42 days with correlation coefficients varying from 0.76 to 0.97 for GPR, IPR and TSP in the three acid soils.
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