Dry matter yield
The mean plant dry matter yield increased significantly with the increasing levels of P up to 90 mg of P kg-1
soil however, the highest mean dry matter yield (16.1 g pot-1
) was recorded with the application of 120 mg of P kg-1
of soil (Table 2). Further increase in the dose of significantly decreased the dry matter yield by 4.6% over 120 mg of P kg-1
. The dry matter yield with RP was lower as compared to SSP at each levels of P irrespective of soil type. Two way and three way interactions were found to be significant. The dry matter yield with the application of P was due to low available P status of the experimental soil. It revealed that optimum mean dry matter yield recorded with 90 mg P kg-1
soil was 2.44 times more than the control. The increases in dry matter yields due to varying levels of P are in agreement with the findings of Singh and Bishnoi (1994)
and Yousaf et al., (2017).
Table 2: Dry matter yield of rapeseed (g pot-1) as influenced by P sources and levels in acidic soils of Meghalaya.
The interaction between different levels of applied P and different rapeseed growing soils was significant for dry matter yield of rapeseed. Tyagi and Rana (1992)
reported that with the application of P fertilizer, the yield of mustard crop significantly increased up to 80 kg P2
which was at par with 100 kg P2
. Similar results were also reported by Prabhuraj et al., (1993)
The data presented in Table 3 indicated that there was a significant increase in phosphorus concentration with different P sources and with the increasing levels of applied P. The lowest mean of P content (0.15 per cent) was recorded in control where no P fertilizer was applied, which was significantly increased with the increase in the doses of P up to 150 mg P kg-1
. The concentration of P at each respective levels of applied P was higher in Inceptisols than Alfisols. The highest mean P concentration was observed in Inceptisols (0.35 per cent) with SSP whereas in Alfisols it was 0.30 per cent. Two way and three way interactions were found to be significant. The increasing P concentration might be due to the availability of more P in soils with the application of P and initial available P status of the experimental soils. Singh et al., (1997)
and Yousaf et al., (2017)
also observed that the concentration of P was significantly improved in both straw and seed of sunflower and rapeseed, respectively due to increased levels of applied P. Similar results were also obtained by Schultz et al., (2018)
for sunflower in North Dakota. The concentration of P was significantly lower in plants grown on Alfisols as compared to Inceptisols owing to less native soil P in these soils.
Table 3: P concentration (%) of rapeseed as influenced by P sources and levels in acidic soils of Meghalaya.
Increasing levels of applied P significantly improved the P uptake by rapeseed plants (Table 4). The overall mean P uptake in control was 9.83 mg P pot-1
, which increased significantly by 4.9 times with the application of 120 mg P kg-1
soil. Irrespective of soils, the P uptake by rapeseed plant showed an increasing trend from no P application to the P level of 120 mg P kg-1
of soil and then reduces. The highest P uptake (59.37 mg pot-1
) was recorded in Inceptisols through SSP compared to RP (49.52 mg pot-1
) whereas in case of Alfisols, highest P uptake (45.23 mg pot-1
) was recorded through SSP as compared to RP (39.06 mg pot-1). Inceptisols had 1.5 times more P uptake under both the P sources and their P levels. The mean P uptake (36.61 mg pot-1
) was recorded through the SSP compared to RP (36.28 mg pot-1
), while in the Inceptisols it was 39.08 mg pot-1
than Alfisols (27.82 mg pot-1
Table 4: P uptake (mg pot-1) in rapeseed as influenced by P sources and levels in acidic soils of Meghalaya.
The data in Table 4 indicated that the application of P significantly improved the P uptake under both the sources irrespective of soils. The mean P uptake increased significantly by 4.89 times over control with the application of 120 mg P kg-1
soil. The mean uptake of P in different rapeseed-growing acidic soils differed significantly among themselves with highest in Inceptisols followed by Alfisols. The dry matter yield of rapeseed was in close association with available P of soils. Similar to these findings, Singh et al., (1997)
reported that the application of P significantly enhanced P uptake in sunflower crop grown on different soils.