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The effect of chromolaena and parthenium as green manure and their compost on uptake and nutrient use efficiency of rice on Typic Paleustalf in Aldur village, Chickmagalore taluk and Chikmagalur district, Karnataka. Two levels of parthenium and chromolaena as green manures and their compost were evaluated. Application of RDF + 7.5 tones of parthenium and chromolaena compost significantly increased the paddy yield over same level of parthenium and chromolaena as green manure.
Recently a noticeable decline in productivity in many of the intensively cultivated areas has been observed. The yield declined is attributed to soil degradation through nutrient and loss of soil quality. It is apparent that sustainability of crop production system in future will mainly depend to a large measure on the adequacy and balanced supply of nutrients. The present experiment was undertaken to study the effects of application of plant nutrients combination with or without organic manure on nutrient uptake and nutrient use efficiency of rice.
2. MATERIAL AND METHODS
The present field trial was started at farmer's field at Aldur village, Chickmagalur taluk, Chickmagalore district, Karnataka state on 2006 under rain fed condition. The soil of the experimental site is Typic Paleustalf. The initial property of the experimental site was: pH 5.38, EC 0.04 dSm-1, total organic carbon 0.98%, NH4+-N 61.10 mg kg-1, NO3- N 10.0 mg kg-1, Brays-P 6.71 mg kg-1 and NH4OAc-K 68.91 mg kg-1. The carbon per cent of parthenium and chromolaena were 39.30 and 38.32 respectively. The ten treatments with three replication in a randomized block design are as follows:
Design : Randomized block design
No. of treatments : 10
No. of replications : 3
Crop : Rice
Variety : Sharavathi
Recommended dose of fertilizer (RDF) : 100: 50: 50 (N: P2O5: K2O)
Plot size : 6 m x 6 m
T1 : Control
T2` : Recommended dose of fertilizer (RDF)
T3 : RDF + Parthenium as green manure @ 5.0 t/ha (RDF + PG1)
T4 : RDF + Parthenium as green manure @ 7.5 t/ha (RDF + PG2)
T5 : RDF + Parthenium compost @ 5.0 t/ha (RDF + PC1)
T6 : RDF + Parthenium compost @ 7.5 t/ha (RDF + PC2)
T7 : RDF + Chromolaena as green manure @ 5.0 t/ha (RDF + CG1)
T8 : RDF + Chromolaena as green manure @ 7.5 t/ha (RDF + CG1)
T9 : RDF + Chromolaena compost @ 5.0 t/ha (RDF + CC1)
T10 : RDF + Chromolaena compost @ 7.5 t/ha (RDF + CC2)
Calculated quantities of compost and green manures were applied to the plots as per the treatments and were thoroughly mixed with the soil. Fertilizers were applied as per details of treatments through fertilizers viz., urea, diammonium phosphate and muriate of potash to supply N, P2O5 and K2O. In all the fertilizer treatments, entire P2O5 and K2O were applied basally. Nitrogen was applied in two splits 50 per cent at planting and 50 per cent at panicle initiation stage. Paddy seedlings were transplanted, the crop was irrigated. Soil samples and plant samples were collected after harvest from each plot. Soil samples were analyzed for available nitrogen  available phosphorus  and available Potassium . Plant samples were oven dried, grinded into fine powder and it was used for analyzing N, P and K content. The nitrogen content was determined by the microkjeldhal method . The phosphorus and potassium contents were determined after the samples were digested with triacid mixture. The phosphorus content was determined by Vanadomolybdo phosphoric yellow colour method and absorbance was recorded at 430 nm with spectrophotometer . The potassium content was determined by using digital flame photometer . The uptake of nitrogen, phosphorus and potassium by rice plant was computed from the formula given below.
Nutrient content (%)
Nutrient uptake (kg/ha) = ---------------------------- x dry weight (kg/ha)
The apparent nutrient use efficiency was worked out as follows
Apparent nutrient use efficiency (%) =
Uptake in treated plot - uptake in control plot X 100
3. RESULTS AND DISCUSSION
Grain and straw yield
The lowest grain yield of 25.77 q ha-1 was recorded in control and highest (45.16 q ha-1) with the application of RDF + chromolaena compost @ 7.5 t ha-1 (Table.1). The yield increase is due to conjunctive application of RDF and organic manures which could be reasoned out that combined application of organic and inorganic nutrients sources increases the availability of nitrogen, phosphorus and potassium in soil and in turn increases the number of tillers, panicle and other growth attributes as a result of better uptake of nutrients from soil . This result is also in close conformity with the findings of several workers on the usage of other green manures in rice production  and .  reviewed the efficiency of the prolonged manurial practices in building up the soil fertility and yield of rice in sandy loam and sandy clay loam soils. Organic matter increased the availability and unavailable plant nutrients by enhancing the biochemical activity of microorganisms.
Lowest grain yield was recorded in control this was quite natural that the inherent soil available nutrients were not sufficient to meet the crop demand under the treatment. The straw yield was greatly improved by the application of RDF + chromolaena compost @ 7.5 t ha-1. The superior performance of the grain yield was observed in the same treatment it is quite natural. Increase in straw yield was mainly due to more number of tillers and plant height. The results are in close conformity with the findings of several workers in the usage of other green manures in rice production  and .
In general, the heavy withdrawal of nutrients from soils and its success depends largely upon surplus amount of fertilizer commensurate with the nutrient uptake. Increase in grain and straw yield was greatly influenced by application of nutrients showed highly significant positive correlation. (Table 1). Application of RDF along with chromolaena compost @ 7.5 t ha-1 (T10: RDF + CC2) recorded highest total NPK uptake, followed by higher level of compost along with RDF. The higher NPK uptake using waste land weeds as green manure, fertilizer and their combination was reported by ,  and . Higher uptake with application of fertilizer treatments and the split application of N compared to organics alone might be due to greater availability of nutrients at early growth stages of crop . Whereas application of organics alone immobilized the available nutrients temporarily at early stages of crop growth ,  and . The increase in P uptake could be attributed to the increased utilization of native P added through enriched composts due to organic acids produced during the decomposition of organic matter. Similar results were obtained by  and . The increased K uptake might be due to the release of K from the organic manures and also due to the action of organic acids which helped in the release of mineral bound insoluble K. These results are in agreement with  addition of compost @ 5.2 metric tonnes resulted in the extraction of 5 times more K by millet crop when compared to control.
Nutrient use efficiency
Application of RDF + chromolaena compost @ 7.5 t ha-1 recorded highest total NPK use efficiency (32, 12 and 31 per cent) followed by RDF + chromolaena compost @ 5.0 t ha-1 (33, 16 and 30 per cent) Due to application organic materials in combination with recommended dose of fertilizer, not only increased yield and nutrient availability and their uptake but also increases nutrient use efficiency.