| Phosphorus (P) is the important macronutrient for plants. It is a component of the key molecules such as nucleic acids, phospholipid, and ATP. P also has a key role in the energy metabolism of all plant cells, so the plants can not grow without a supply of this nutrient, but the availability of phosphorus in the soil is very low because most are in the form of insoluble compounds and not available for plants, so phosphorus is often deficient. Phosphorus fertilizer application in low soil P availability is needed to meet crop requirements. Chemical P fertilizers are efficient in providing P for plant requirement, but the production of chemical fertilizers is expensive. Phosphate rock is one of P sources that can be used as fertilizer, although the availability of P is lower than chemical fertilizers, but it is more economically use due to the low cost per unit of P, and effective under specific condition of soil management.A pot experiment was conducted to investigate the effect of phosphate rock application on alfalfa production and macronutrients compared to chemical phosphate fertilizer in latosol soil. Three rates of phosphate fertilizers (75,100, and 125 mg P2O5/kg) were applied to the soil as Guizhou phosphate rock (GPR), Jingxiang phosphate rock (JPR) and single superphosphate (SSP).The results showed that alfalfa growth responsed to P fertilizer treatment. The height of the plant, number of tillers and number of leaves were significantly increased with phosphorus application compared to control treatment. The highest plant height was 95.80 cm by the JPR 75. The best number of tiller was 36 with GPR 125. There was no significant different between JPR 75 and SSP 125 in the number of leaves (1394 and 1219, respectively). There was an interaction between source and level of P fertilizers for all yield parameters. The source and level of P fertilizers had no significant effect to stem and total fresh yield, and stem dry yield. Leaf and total dry yield were not significantly affected with the source of P fertilizers, whereas the level of P fertilizers had no significant effect to leaf fresh yield. There was no significant difference between JPR 75 and SSP 125 in increasing leaf and total fresh yield, but JPR 75 was better for increasing stem fresh yield than others. The best forage dry yield was resulted by JPR 75 and SSP 125 applications. There was no significantly different between them for increasing forage dry yield. The highest values were in the treatments of JPR 75, JPR 100, SSP 125 and the control treatment (0.62,0.61,0.60 and 0.59, respectively). The highest leaf N content was 27.49 g/kg in JPR 125 which had no significant difference with JPR 100 as 26.61 g/kg. The highest stem N content values were in SSP 125, GPR 100 and control (11.83,11.31 and 10.94 g/kg, respectively) followed by the others. The source and level of P fertilizers and the interaction among them were significantly affected the phosphorus concentration in both of alfalfa leaf and stem which the highest values were in JPR 100, SSP 100, JPR 125 (4.48,4.22,4.18 g/kg, respectively) for the leaf and GPR 125, SSP 100 (5.23,5.13 g/kg, respectively) for the stem. The highest values of potassium content in leaf were obtained by addition of JPR 75 and SSP 100 (36.18 and 33.96 g/kg, respectively). There was no significant difference between the treatments compared to the control for potassium content in stem where the highest values were obtained by SSP 125, JPR 125, JPR 100 and control.The leaf, stem and total P-uptake of P application were significantly different compare to the control. JPR 75 and JPR 100 resulted the highest value in leaf P-uptake, whereas the highest values of stem P-uptake were resulted by SSP 100, GPR 125 and SSP 125. However, the best value was 53.77 mg/pot obtained by SSP 100 for the total P-uptake. Relative agronomic effectiveness (RAE) decreased with increasing P level in both of phosphate rocks. The best RAE was obtained by addition JPR 75 (252.15%). The phosphorus utilization ratio (PUR) was significantly affected by the different source of P, level of P fertilizers and interaction between them. The result showed that PUR decreased with increasing P level in all sources of P. SSP was superior to GPR and JPR in the same level of P. The highest value was 20.61% obtained by SSP 75.The different source of P fertilizers significantly affected the P fraction in soil, except A1-P. There was no significant effect of P level to Ca-P and Al-P but its significance to Fe-P and O-P. There was no interaction between source of P and level of P fertilizer to Ca10-P and O-P. P fractions showed the same tendency in all treatments:O-P> Fe-P> Ca10-P> A1-P> Ca2-P> Ca8-P. Most of P in latosol soil were in the form of Fe-P and O-P.The highest total N value was 1.25 g/kg obtained by JPR 100 followed by JPR 75, JPR 125, GPR 100, SSP 125 in the same value (1.20 g/kg) and SSP 100 (1.73 g/kg). The highest values of total P in soil were in the treatment with JPR 100, SSP 125, JPR 100 and SSP 100 (1.49,1.49,1.47 and 1.46 g/kg, respectively). There was no significant difference between the treatments compared to the control for total K in soil. The highest values were 1.28,1.27 and 1.27 g/kg obtained by GPR 100, SSP 75 and control, respectively. The best interaction between P sources and P level was 81.95 obtained by SSP 75 followed by SSP 125, JPR 125, and SSP 100 (79.07,78.42 and 77.67 mg/kg, respectively) for soil available N. The highest available P value was 25.52 mg/kg by addition 100 mg/kg of Guizhou PR. The treatments were significantly different compare to the control for available K in latosol soil. The highest values were SSP 75, JPR 125, GPR 75, SSP 100, and GPR 125 (307.90,307.34,303.90,301.98 and 299.48 mg/kg, respectively). JPR was better than GPR to improve soil organic carbon, whereas no significant difference with SSP in the level 75 and 100 mg/kg of P fertilizers. The interaction between P source and level of P obtained the highest result was 14.80 g/kg by JPR 100 application which had no significant difference with JPR 125 and SSP 100 (14.77 and 14.57 g/kg, respectively). The soil pH was increased with P fertilizers application which the highest value was obtained by JPR 125 (6.86). |
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