Residual Effect of Composts on Soil Fertility Under Amaranthus-Turmeric Cropping System

In amaranthus-turmeric cropping system, turmeric (var. BSR 2) was raised after amaranthus to assess the residual effect of composts on soil fertility. The experiment was conducted without disturbing the original treatment structure. Significantly higher residual effect was observed in those plots which had received compost of banana pseudostem or sugarcane trash prepared with different starter materials viz ., Cow dung and sewage sludge, accelerator ie., Microbial inoculum viz. , Pseudomonas and Bacillus sp and Trichoderma viride , accelerator cum enricher materials like Urea and Poultry manure than the raw materials. In general, the performance of Poultry manure enriched microbial inoculum or Trichoderma viride compost of banana pseudostem or sugarcane trash @ 750 kg ha -1 with 75 per cent of the recommended dose of fertilizer (RDF) was quite impressive than that of no manure i.e., 100 per cent RDF alone and the absolute control in enhancing available nutrient (N, P and K) status, organic carbon and cation exchange capacity at post harvest stage of residual crop of turmeric. The residual effect of composts prepared with banana pseudostem was considerable than that with sugarcane trash. The highest available N, P, K, organic carbon and cation exchange capacity of 236 kg ha -1 , 16.72 kg ha -1 , 482 kg ha -1 , 0.64 per cent and 20.73 cmol (P + ) kg -1 respectively was recorded with the application of poultry manure enriched microbial inoculant compost of banana pseudostem @ 750 kg ha -1 with 75 per cent of the recommended dose of fertilizer.

Organic manures besides supplying some amount of the essential nutrients to the current crop often leave substantial residual effect on the succeeding crops in the system and this residual effect lasts for several seasons (Seshadri Reddy et al., 2005).This paper reports the residual effect of composts on soil fertility under amaranthusturmeric cropping system.

Materials and Methods
A field experiment was conducted during 2004 -2005 in farmer's field at Alanthurai, Coimbatore district, Tamil Nadu, using amaranthus (var.CO2) as test crop to find out the effect of composts on nutrient uptake and green yield of amaranthus.The residual crop turmeric (var.BSR 2) was raised in the same field of amaranthus after harvesting, to know the residual effect of raw and composted base materials viz., banana pseudostem and sugarcane trash on soil fertility without disturbing the original treatment structure.The initial soil available N, P, K, Organic carbon and CEC was 165 kg ha -1 , 10.40 kg ha -1 , 413 kg ha -1 , 0.50 per cent and 15.0 cmol (P + ) kg -1 ) respectively.The experimental field was ploughed well to obtain fine tilth and leveled.The field was then divided into 60 plots of 20 M 2 (5 x 4 M 2 ) size leaving 0.5 M spacing between each plot and 1 M between each block for irrigation purpose.The experiment was laid out in randomized block design and replicated thrice.The experiment comprised of eight treatments for composted banana pseudostem and sugarcane trash separately, 100 per cent recommended dose of fertilizer (RDF) alone and absolute control, i.e., F0C0 : Absolute control; F1C0 : Recommended dose of fertilizer (RDF 120:60:90 kg ha -1 N, P2O2 and K2O respectively); F1C1: Raw base material @ 5 t ha -1 + 100% RDF; F2C2 : Cow dung slurry compost @ 750 kg ha -1 + 75% RDF (90:45:67.5kg ha -1 N, P2O5 and K2O respectively) ; F2C3: Sewage sludge compost @ 750 kg ha -1 +75% RDF; F2C4: Microbial inoculum compost @ 750 kg ha -1 + 75% RDF; F2C5: Microbial inoculum + poultry manure enriched compost @ 75 kg ha -1 + 75% RDF; F2C7: Trichoderma viride + urea enriched compost @ 750 kg ha -1 +75% RDF and F2C9: Trichoderma viride + poultry manure enriched compost @ 750 kg ha -1 + 75% RDF.All the improved agronomic practices were adopted appropriately.The composts were applied only to amaranthus and only inorganic fertilizers were applied to turmeric.The fertilizer was applied @ 120:60:90 kg N, P2O5 and K2O ha -1 respectively.The P2O5 was applied basally and N and K2O were applied as split doses at 30, 60, 90 and 120 DAP.The crop was harvested 10 months after planting.The rhizome yield was recorded separately for each plot.The soil samples were collected at post harvest stage of turmeric from each treatment plot.The collected soil samples were shade dried, processed and sieved through 2 mm sieve and stored in polythene bags, for carrying out the analysis.The collected samples were analyzed for their organic carbon content, cation exchange capacity and macronutrients status by adopting standard procedures.The results of the study are presented below.

Results and Discussion
The status of soil available N, P and K after the harvest of turmeric changed significantly due to different treatments imposed to the previous crop of amaranthus.Application of poultry manure enriched Comparison made between raw organics @ 5 t ha -1 with 100% RDF and composted organics @ 750 kg ha -1 with 75% RDF banana pseudostem or sugarcane trash composts prepared with microbial inoculum or Trichoderma viride @ 750 kg ha -1 ( F2C6) in conjunction with 75 per cent of the RDF significantly increased the  Sugarcane trash 11.1 14.9 15.2 13.9 14.7 15.9 13.5 14.7 15.9 soil ranged from 142 -236 kg ha -1 (Table 1), 8.40 -16.72 kg ha -1 (Table 2) and 324 -482 kg ha -1 (Table 3) respectively.The composts prepared with banana pseudostem were superior to sugarcane trash.The comparison made among all the composts applied treatments,the F2C6 compost of banana pseudostem recorded significantly higher alkaline KMnO4 -N, Olsen -P and neutral normal NH4OAC-K.Comparison made between raw organics @ 5 t ha -1 with 100% RDF and composted organics @ 750 kg ha -1 with 75% RDF The buildup in available nutrients status of soil through organic sources, in this case, the composts of banana pseudostem / sugarcane trash could be attributed to the residual effect of applied fertilizers and to the mineralization of organic sources (or) solubilization of the nutrients from the native source during the decomposition process (Patel and Patel, 2003).

Organic carbon and cation exchange capacity
The data on organic carbon (Table 4) and CEC (Table 5) of soil after the harvest of turmeric indicated Comparison made between raw organics @ 5 t ha -1 with 100% RDF and composted organics @ 750 kg ha -1 with 75% RDF that the different treatments imposed to the previous crop of amaranthus significantly affected these parameters.The highest organic carbon content (0.64%) and CEC (20.73 cmol (P + ) kg -1 ) were associated with the application of 750 kg ha -1 of poultry manure enriched microbial inoculum or Trichoderma viride compost of banana pseudostem or sugarcane trash with 75 per cent of the RDF and the lowest were found under absolute control.
The increase in the organic carbon and CEC of soil owing to the application of banana pseudostem or sugarcane trash composts prepared with different starter or accelerator with or without enrichment in conjunction with 75 per cent of the RDF to the previous crop of amaranthus could be attributed to their residual effect.The higher organic carbon content could also be ascribed to the fact that these composts can be easily decomposed because of their narrower C/N ratio as reported earliest by Bellaki and Badanur (1994).

Conclusion
In general, the performance of poultry manure enriched, microbial inoculum or Trichoderma viride composts of bananapseudostem or sugarcane trash @ 750 kg ha -1 with 75 per cent of the RDF was quite impressive than that of no manure in enhancing the available nutrient (N, P and K) status, organic carbon content and cation exchange capacity at post harvest stage of residual crop of turmeric.
available N, P and K status, when compared to the other composts / raw base materials / 100 per cent NPK alone / absolute control.The alkaline KMnO4 -N, Olsen -P and neutral normal NH4OAC -K status of

Table 2 . Effect of compost on soil available P (kg ha -1 ) at post harvest stage of turmeric Comparison made between absolute control and RDF
Comparison made between raw organics @ 5 t ha -1 with 100% RDF and composted organics @ 750 kg ha -1 with 75% RDF