Interaction between P and Zn on the Changes in Different Inorganic Phosphorus Fractions under Waterlogged Soil Treated with and Without Organic Matter

Interaction can be defined as the influence of an element upon another in relation to growth and crop yield. There are mainly two types of interactions effect viz. antagonistic and synergistic effects. Antagonistic effect means an increase in concentration of any nutrient element will decrease the activity of another nutrient (negative effect). While synergistic effects means an increase of concentration of any one nutrient element will influence the activity of another nutrient element (Positive effect). Nutrient antagonism occurs when an excess  of a particular element blocks the absorption of another element the plant needs and can happen with elements of a similar size and charge (positive or negative) (Bhardwaj et al., 2019). Phosphorus and zinc are two essential nutrients which are required for normal plant growth. These nutrients are mutually antagonistic in certain circumstances which can cause yield reductions in many crops due to either P or Zn deficiencies. Deficiencies typically happen when a nutrient is available in small amounts. In this phenomenon, the nutrient is present in marginal to normal levels but the antagonizing nutrient is available in such a large amount that it induces the deficiency of the other. The Zn induced P deficiency is a very rare phenomenon because growers commonly apply large amounts of P fertilizer as compared to Zn fertilizer. Organic matter causes soil to clump and form soil aggregates, which improves soil structure. With better soil structure, permeability (infiltration of water through the soil) improves, in turn improving the soil’s ability to take up and hold water.  The addition of organic manure may reduce the mobility of Zn in soil by forming stable chelates thereby may affect the formation of Zn-P complexes in soil (Banik and Samat 2016). The FYM is one of the most widely used organic in the study area. Thus, the present study was undertaken to find the interaction between P and Zn on the changes in different inorganic phosphorus fractions under waterlogged soil treated with and without organic matter.

An incubation experiment has been conducted in the laboratory of Department of Agricultural Chemistry and Soil Science, University of Calcutta to find the interaction between P and Zn on the changes in P content under waterlogged soil treated with and without organic matter. For this experiment, the surface soil was collected (0-15 cm depth) from the cultivated field of Baruipur Experimental Farm of University. Before analysis, the soil was air dried ground and passed through 2mm sieve. The surface soil samples were analyzed for various soil properties such as pH and EC (Jackson, 1973), organic carbon (Walkley and Black, 1934), Cation exchange capacity (Harada and Inoko, 1980) and available P₂O₅ by Olsen’s method (Olsen et al., 1954), Available K₂O by Flame photometric method (Jackson, 1973), Available N by modified Kjeldahl’s method (Jackson, 1973). The physico-chemical properties of the soil were:  pH 6.46, EC: 0.05 dSm^-1; Organic Carbon:  6.5 g kg^-1; CEC: 15.76 cmol (p+) kg^-1; Available N: 0.2508 g kg^-1; Available P by Olsen method : 0.0153 g kg^-1; Available K: 0.29008 g kg^-1; Available Zn: 0.00055 g kg^-1. In this present investigation, the source of P used was Potassium dihydrogen phosphate (22% P₂O₅) and the source of organic matter was Farm Yard Manure (FYM) in which Total N content was 9.6g kg^-1, Total P content was 6.5 g kg^-1, Total K content was 10.2 g kg^-1 and Total Zn content was 1.5 g kg^-1. After application of all treatments, maintaining waterlogged condition, the soils were allowed to incubate at room temperature (30±2)°C for a period of 10, 20, 30, 40, 50 days interval and analyzed for different fractions of P by following the procedure of Kuo, (1996).
 
Details of experiments
 
Moisture regime: Waterlogged.
Replication: Three.
Design: 2 Factor Factorial CRD.
 
Treatments details
 
P₀Zn₀ -   No Phosphorus + No Zn.
P₀Zn₁ -    No Phosphorus + Application of Zn at 2.5 mg/kg soil.
P₀Zn₂ -   No Phosphorus + Application of Zn at 5 mg/kg soil.
P₁Zn₀ -    Application of P at 10 mg/kg soil + No Zn.
P₁Zn₁ -    Application of P at 10 mg/kg soil + Application of Zn at 2.5 mg/kg soil.
P₁Zn₂ -   Application of P at 10 mg/kg soil + Application of Zn at 5 mg/kg soil.
P₂Zn₀ -   Application of P at 15 mg/kg soil + No Zn.
P₂Zn₁ -    Application of P at 15 mg/kg soil + Application of Zn at 2.5 mg/kg soil.
P₂Zn₂ -   Application of P at 15 mg/kg soil + Application of Zn at 5 mg/kg soil.
               
Under this experiment, organic matter has been applied @ 1% by weight of the soil in one set of all treatments and another set of all treatment have been conducted without organic matter.

The results (Table 1a, 2a, 3a, 4a and 5a) show that the pattern of changes in the amount of loosely bound P, Al-P, Fe-P, Reductant soluble P and Ca-P fractions under waterlogged soil without amended with organic matter showed a consistent decrease in the amount throughout the incubation period. This lowering of phosphorus content with the application of zinc may be attributed to the antagonistic interaction of P and Zn. Due to absence of organic matter, no counter effect of decreasing trend was observed with respect to each P fraction. The data also revealed that all inorganic fraction of phosphorus content increased markedly with the increase of P application in all the cases where zinc was not applied and showed the lowest value of loosely bound P, Al-P, Fe-P, RS-P and Ca-P where zinc and phosphorus were applied at their highest doses.
 

 

 

 



       
The results (Table 1b) show that the amount of loosely bound P due to organic matter application under waterlogged condition showed a consistent decrease throughout the period of incubation irrespective of treatments with the exception of slight increase at 20 days period of incubation, being varied with different treatment combination. Mandal et al., (1973) reported that the application of organic matter increased the release of added P which confirms the results of present investigation. The decrease of loosely bound P due to individual application of both P and Zn varied and followed a similar trend to that of loosely bound P, being showed a significantly lower amount of this fraction at the later period when Zn was applied, while relatively greater amount was recorded with treatment when P was applied at its increasing level which is obvious in presence of organic matter under waterlogged condition. As regards to the interaction between P and Zn in presence of organic matter, it was observed that although the amount decreases but at a slower rate which might explained by counter effect of added organic matter restricting the antagonistic effect between P and Zn (Das, 2018). Das et al., (2005) also reported similarly who showed that the amount of available P increased initially and decreased at the later period. The results (Table 2b) reveal that the amount of Al-P fraction showed a slight initial increase and thereafter the amount of the same decreased consistently throughout the incubation period irrespective of treatments in presence of organic matter. However, the amount varied with treatments. The individual application of both P and Zn and their combinations although increased initially but at the later period of incubation, the amount of Al-P fraction showed a consistent decrease. However, the magnitude of such decrease has been found to be much higher in the treatment where higher level of Zn (5 mg kg^-1) was applied compared to individual application of P at its higher level (15 mg kg^-1). Comparing the results of their interaction effects, it was found that the amount of such decrease was much less which might be attributed to the counteracting the negative effect of P x Zn interaction in presence of organic matter. The results of the present investigation also find support from the findings of Patel et al., (1992) who reported that the application of graded doses of P significantly increased various fractions of P including Al-P fraction. The application of organic matter at 2.5 and 5 per cent significantly increased the content of occluded P and Olsen’s P. The results (Table 3b) reveal that the amount of Fe-P fraction showed a slight initial increase and thereafter, the amount of the same decreased consistently throughout the incubation period irrespective of treatments in presence of organic matter. However, the amount varied with treatments. The individual application of both P and Zn and their combinations although increased initially, but at the later period of incubation, the amount of Fe-P fraction showed a consistent decrease. However,  magnitude of such decrease has been found to be much higher in the treatment when higher level of Zn (5 mg kg^-1) was applied compared to individual application of P at its higher level (15 mg kg^-1). Such initial increase might be explained by the added effect of organic matter which contributes P in the soil solution. Comparing the results of their interaction effects, it was found that the amount of such decrease was much less which might be attributed to the presence of organic matter  counteracting the negative effect of P X Zn interaction. Agrawal et al., (1987) reported that Fe-P showed the highest increase over control among other fractions. The results (Table 4b and Table 5b) show that the trend of changes in the amount of reductant soluble P and Ca-P fractions showed a similar pattern to that of Fe-P fraction. But the absolute amounts of those fractions were varied with other fractions. The absolute amount of reductant soluble P was lower than that of both Fe-P and Ca-P fractions in presence of organic matter. The results also show that Ca-P fraction was the dominant inorganic phosphorus fraction which can play a major role for P nutrition of rice in addition to Fe-P and Al-P fractions. Sihag et al., (2005) reported that the amount of P recovered in Ca-P form increased significantly with the application of organic matter over control.
 

 

 

 

These results clearly demonstrated that the antagonistic effect of phosphorus and zinc is prevailed in soil which affects the mobility of both nutrients in soil-plant systems. The addition of organic matter can decrease this antagonism, to some extent, between these elements may by forming complexes with both. Significant positive interaction between phosphorus and organic matter (P×FYM) was also noted. The results also show that Ca-P fraction was the dominant inorganic phosphorus fraction which can play a major role for P nutrition of rice in addition to Fe-P and Al-P fractions.

None.