Study on Direct Application Possibility of Phosphate Rock in Calcareous Soils

The conjunction of calcareous parent materials and dry climate has resulted in the development of calcareous and alkali soils in large areas of Iran. Due to the high levels of Ca++ in soil solutions and high pH values, the soil nutrients, whose absorptions depend on pH, will become less available and thus limit the growth of crop plants. The objectives of this experiment was to test the possibility of using rock phosphate along with sulfur, thiobacillus (SOM), phosphate solubilizing microorganisms (PSM) to provide phosphorus to feed corn in calcareous soils. A completely randomized experiment with 15 treatments and 3 replications and 3 separate cuttings was carried out in the Soil and Water Research Institute greenhouse during 2001 for this investigation. The treatments included: T1=the control; T2= triple super phosphate (TSP); T3= phosphate solubilizing microorganisms (PSM); A= rock phosphate (A); T5= A+PSM; T6= A+PSM+organic matter (OM); T7= A+OM; T8= A+ sulfur (S); T9= A+S+OM; T10= A+S+SOM; T11= A+S+OM+SOM; T12= A+S+SOM+ PSM; T13= A+S+OM+SOM+PSM; T14= A+S+PSM; and T15= A+S. Planting, protection and cutting at three stages (4 weeks, 8 weeks and 12 weeks), and the analysis of data on dry weight yields, and the level of phosphorus absorption by plants were carried out similarly for all the treatments.The results show that for earlier cuttings when very little phosphorus from rock phosphate had been released and utilized by the plant triple super phosphate treated samples produced more dry weight. However, the dry weights of the later cuttings were significantly the same for triple superphosphate treated and rock phosphate treated plants. The results also showed that adding organic matter to any treatments containing microorganisms as the base treatment led to reduced yields which may be due to the type of organic matter to pure inorganic treatment mixtures except for A+S, however, resulted in yield increases. This finding emphasizes the negative effects of tea residue on phosphate solubilizing and sulfur oxidizing microorganisms. This experiment also showed that adding phosphate solubilizing microorganisms to sulfur or thiobacillus containing treatment mixtures would lead to lower yields indicating the negative effects of the two microorganisms. The efficiency of treatment 2 (triple super phosphate) was greater for the first and second cuttings and showed significant differences with respect to the other cuttings, whereas with the third cuttings even though the maximum yield was obtained with triple super phosphate treatment (14.66 gr/pot) it was significantly the same as T10 (12.67 gr/pot), T11 (12.37 gr/pot) and T12 (12.01 gr/pot) at 5% level. The results, therefore, show that that under greenhouse conditions rock phosphate along with sulfur, and thiobacillus organisms provides corn with the required phosphate, greater population densities and a better selection of thiobacillus, as well as the type of organic matter along with field evaluations are recommended. There are many source of Apatite in the world that can be use as P fertilizer. But previous research show that this source of P have no advantage if it be used lonely, because it's solubility especially in alkaline soils (Widespread in Iran) is very low. We supposed that compost or PSB (Phosphate-solubilizing microorganisms) could promote solubilization of apatite. An Experiment was conducted to evaluate the urban compost and apatite resources interaction with Bacillus (as important Phosphate solubilizing bacteria) in rhizosphere of Corn and their effects on P uptake, yield and yield component of corn. Four factors: 1- apatite 2-urban compost 3-Bacillus 4-Sulphur inoculated whit Thibacillus sp. was factorially applied in two levels in Complete Randomized Block Design in research farm of soil and water research institute, Karaj, Iran, in two years. The results show that interaction of compost and Bacillus megaterium on yield of maize is significant (P0/05).These treatments increase yield of corn. Apatite has significant reverse effect on growth and colonization of Bacillus and reduced corn yield and didn't increase the soluble P in corn rhizosphere. We conclude that the Environmental condition of experiment in these studies is very important and could influence performance of Apatite and PSMs.