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DYNAMICS OF PHOSPHORUS FRACTIONS IN THE CALCAREOUS SOILS OF SAURASHTRA REGION

KrishiKosh

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Title DYNAMICS OF PHOSPHORUS FRACTIONS IN THE CALCAREOUS SOILS OF SAURASHTRA REGION
 
Creator Mr. M. S. Solanki
 
Contributor Dr. B.A. Golakiya
 
Subject null
 
Description The crop response to phosphorus in the soils of Saurashtra is enigmatic. Since the soils are calcareous in nature the dynamics of P in these soils have became more complicated. It was desired to study the P fractions in the soils with following objectives:
1. To determine the turn over of phosphorus fractions in the different soil groups of Saurashtra region.
2. To investigate the status of phosphorus fractions (Saloid-P, Occl-P, Red-P, Al-P, Fe-P, Ca-P) in medium black calcareous soils (Vertic Ustocrepts) of Junagadh under LTFE.
3. Modeling the dynamics of phosphorus fractions in these soils.
To achieve the forgoing objectives whole work is divided in two parts. The part one (I) comprised regular monitoring of the fertility since 1990. Samplings were made from the soils of predetermined survey number at ten years intervals. The samples of 1990 and 2000 were subjected to analysis fractionation of phosphorus viz., Saloid-P, Occluded-P, Reductant Soluble-P, Al-P, Fe-P, Ca-P. Various soil properties such as pH, EC, CaCO3, CEC, Ex. Ca, OC, soil clay, ESP, soil available nitrogen, phosphorus and potash and soil-heat soluble sulphur were also analyzed. Whole set of data from ten different soil groups of Saurashtra region and changes in a long term cycle of 10 years were subjected to various statistical analyses including correlation among fractions, between the forms and with properties, stepwise regression, multiple correlations and path analysis with available phosphorus as the dependent variable to investigate the influence of long term cycle, interaction and soil properties on available form of phosphorus vis-à-vis finding out the depletion of predominant component of available phosphorus and correlation among various forms and fractions of soil groups.
Second part (II) of investigation comprised the samples derived from long-term fertilizer experiment initiated 20 years back on Vertic Ustocrepts calcareous medium black clayey soils of Junagadh. As per the treatments (T1: Control, T2: FYM @ 25 t ha-1, T3: ½ NP, T4: ½ NP+K, T5: NP, T6: NP+K), there were gross additions of phosphorus in groundnut-wheat-sorghum cropping system. The phosphorus, their fractions and soil properties at 10th and 20th years interval were related to various yields and NPK contents from plants. In this part also the data were subjected to correlation analysis, stepwise regression, multiple correlation and path analysis.

I. Soil Survey
The survey of various soil groups of Saurashtra region indicated that all the soil groups are fairly rich in total-P. In general, considerable portion was of inorganic-P (90.5 %), while minor portion was of organic-P (9.5 %). Among the different six inorganic-P fractions, major part of about 67.0 per cent was Ca-P only and the remaining five inorganic-P fractions in decreasing order were RS-P, Al-P, Fe-P, saloid-P and occluded-P. The status of these P-fractions varied with individual soil groups. Overall, the different P-fractions viz., available-P (37.5 %), RS-P (4.76 %) and Ca-P (2.84%) were found to decline, whereas, occluded-P (12.61%), Al-P (12.02%), saloid-P (10.32%) and Fe-P (5.03%) were found to increase after a span of ten-year. There was the depletion either from higher category to medium or medium category to low one for available-P in Saurashtra region in one-decade but its variation varied with individual soil group. Although Ca-P is the most abundant P-fraction in the earth crust but its’ availability requires suitable management at the earliest in the soils of Saurashtra region. The dynamics of P–fractions, in general, exhibited gross negative trend with varying magnitude according to soil, climate, agronomy and cropping pattern followed in the region.
Available-P exhibited a significant positive correlation with Al-P and negative with Fe-P and Ca-P. Most of the inorganic–P fractions were correlated with each other positively or negatively. The significant positive relationship of inorganic-P with Al-P and Ca-P was in most of all the soil groups except in the Stoney.
Stepwise regression analysis values for available-P with inorganic-P fractions as well as with soil properties were low or zero in most of the soil groups. However, the occluded-P followed by saloid-P and RS-P behaved positively and Fe-P negatively in SBBT, the occluded-P and Al-P positively in CS, the Fe-P negatively in SBSS and Al-P positively in RAD were influenced on the available–P. The soil CEC in SBBT and soil clay in MBLS groups had the positive influence on available-P. The values of multiple regressions of available-P with various inorganic-P fractions and with different soil properties varied with soil groups.
In path co-efficient analysis, the inorganic-P fractions viz., Al-P, occluded-P and RS-P had more direct positive, whereas, Ca-P, saloid-P and Fe-P had more direct negative influence on available-P in different soil groups but its indirect effect varied with the soil groups. The soil properties i.e. CaCO3, pH, EC, CEC and OC had more direct positive influence on available-P while, Ca-P had more direct negative effect on available-P. The indirect effect of the different soil properties on available-P varied with individual soil groups.

II. Long Term Fertilizer Experiment (LTFE)
In the LTFE differences in yield diminished in groundnut while T6 recorded highest values in wheat as well as sorghum all through. The N content was highest in T6 in a long run in groundnut and wheat grain while in straw it declined. Phosphorus in groundnut increased while that in cereals declined over 20 years. Potash also followed more or less same trend.
The optimal and sub optimal dose of NP/NPK over control (no any fertilizer application) had significantly increased the most of the inorganic-P fractions except Ca-P after a span of two decade. The application of FYM more or less maintains the soil fertility status whereas application of K had no any significant influence on any P-fractions of soil. While there ware depletion of inorganic-P, total-P and available-P with any of the fertilizer treatments. But that of organic-P increased with the most of the fertilizer treatment except control. The chemical fertilizers appeared to supplement as well as trigger the utilization of different P-fractions.
None of the relationship between available-P and the crops yield was significant. But in case of P-fractions, positive correlations were found in many cases. The correlation of available-P with NPK content and uptake by the crops were seen only in few cases.
The stepwise regression analysis of Av-P with inorganic-P fractions indicated that Fe-P was the only–P fraction, which has influenced the available-P. The value of multiple correlations co-efficient maintained higher level for the available-P with various inorganic-P fractions.
In the path co-efficient analysis, the direct high positive and negative influences of Ca-P and RS-P on available-P, respectively, were noted in the LTFE.
 
Date 2017-04-03T11:04:28Z
2017-04-03T11:04:28Z
2005-09
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/5810006728
 
Language en
 
Format application/pdf
 
Publisher JAU, JUNAGADH