Effect of Time of Application and Organic Sources of Nitrogen On Drymatter Accumulation and Nutrient Uptake at Different Stages of Rice ( Oryza Sativa L.)

A field experiment was conducted at the Agricultural College Farm

Modernized agricultural practices using high rate of fertilizer and agrochemicals destroy the soil ecosystem, which in turn decrease nutrient availability and degrade soil properties (Ladha et al., 2000). Among the various yield determining factors, soil fertility is of prime importance. Our soils are low in nutrients due to continuous cropping and inadequate use of organic manures and excessive use of inorganic fertilizers. Nitrogen is a crucial nutrient for rice growth, and its deficiency is a major constraint to stable rice production worldwide. Suzuki (1997) reported increased rice yield with increasing uptake of N until reaching a peak. Soil N supply plays a dominant role in the N nutrition of wetland rice as one-half to two-thirds of the total N taken up by rice crops even in N-fertilized paddy fields comes from the soil N pool (Sahrawat, 1983b). However, soil fertility has progressively declined due to plant nutrient depletion in most of the fields with only the application of chemical fertilizers (Ladha et al., 2000).
In order to ensure better crop production, efforts are needed to maintain soil fertility through the use of organic manures. Organic manures play an important role in maintaining soil fertility and productivity and they act as a reservoir of plant nutrients. Indiscriminate use of chemical fertilisers cause ill effects to both the environment and human beings. It is convenient to provide organic manure to replace the inorganic material partly or completely. It is, therefore, important to promote economically viable and environmental friendly interventions for sustainable agriculture. Application of animal waste *Corresponding author email : sujatha.agro12@gmail.com manures, which contain both mineral and organic N, is useful for maintaining and improving soil fertility and rice production (Takahashi et al., 2004). Basal application of organic manures has low nitrogen use efficiency and higher losses due to leaching and denitrification. Application of appropriate quantity of nitrogen as split doses will meet the crop demand and enhance the nutrient uptake at critical stages (10 days before panicle initiation) without causing much loss. Hence, use of organic sources like FYM, poultry manure, vermicompost and neemcake deserve priority for sustained production and better utilization in organic rice production. Organic manure has been proven to enhance efficiency and reduce the need for chemical fertilizers (Sahrawat, 2006). Hence, this experiment was undertaken to find out the effect of organic sources of nitrogen on drymatter accumulation and nutrient uptake of rice.

Materials and Methods
A field experiment was conducted at Agricultural College Farm, Bapatla, during kharif 2012. The experiment was laid out in a randomized blocks design and replicated thrice. The soil of the experimental site was clay loam in texture, slightly alkaline in reaction (pH 7.9) with 0.43 % organic carbon and 210, 29 and 385 kg ha-1 of N, P and K. The experiment consisted of nine treatments viz., 100% RDN through inorganic sources (120:60:40 kg N, P 2O5, K20)(T1), 100% RDN through poultry manure (10 days before puddling) (T2), 100% RDN through FYM (10 days before puddling) (T3), 100% RDN through neem cake (10 days before puddling) (T4), 100% RDN through vermicompost (10 days before puddling) (T5), 50% RDN as basal +50% at 10 days before PI stage through poultry manure (T6), 50% RDN as basal +50% at 10 days before PI stage through FYM (T7), 50% RDN as basal +50% at 10 days before PI stage through neem cake (T8), 50% RDN as basal +50% at 10 days before PI stage through vermicompost (T9). Well decomposed poultry manure, FYM, neemcake and vermicompost with 2.0 %, 0.5%, 2.5 % and 1.2 % N respectively, were used as organic sources for nitrogen. Based on the equal N basis, the required quantities of organic manures were incorporated in the soil 10 days before puddling. In the treatment T1, recommended doses of 120:60:40 kg ha-1 of N,P and K in the form of urea (46% N), single super phosphate(16% P20 5) and muriate of potash(60% K20) were applied to the rice crop. The nitrogen was applied in three splits i.e. 1/2 as basal, 1/4 at maximum tillering and 1/4 at panicle initiation stages. Entire dose of phosphorus was applied basally before sowing. Half of the potassium was applied basally and remaining half was applied at panicle initiation stage. The consumer preferred rice variety, BPT-5204 (Samba Mahsuri) was raised. Thirty day old seedlings were transplanted using two seedlings hill-1 with a spacing of 20 ×15 cm. Recommended agronomic practices and plant protection measures were followed.

Drymatter accumulation
Drymatter accumulation at different growth stages was significantly influenced by organic manures and recommended NPK through fertilizers (Table1). The results of the investigation revealed that higher drymatter accumulation was obtained with application of recommended dose of chemical fertilisers which was significantly superior to 100% RDN through poultry manure (T2) at 30 DAT but on par at 60 DAT and both the treatments recorded markedly higher dry matter accumulating than the other treatments. At 90 DAT and at maturity, significantly higher drymatter accumulation was observed with T1, which was on par with 50% RDN as basal+ 50% at 10 days before PI stage through poultry manure (T6) but proved significantly superior to the rest of the treatments. The treatment T6 remained on par with 100% RDN through poultry manure (T2).
Significantly higher drymatter accumulation in fertilized treated plots might be due to greater solubility and accelerated release of nitrogen and by providing an opportunity time for rice to utilize higher quantum of nutrients. Increased drymatter accumulation in poultry manure and vermicompost  (2001) and Altaf Hussain et al. (2012).

Yield
The highest grain and straw yield (5856 and 6902 kg ha-1, respectively ) of rice was obtained with the application of 100% RDN through fertilizer (T1) which was however, on par with 50% RDN as basal+50% at 10 days before PI stage through poultry manure (T6) but proved significantly superior to the rest of the treatments (Table 1).
Higher yield with recommended dose of chemical fertilizer was due to better growth of plants and better yield attributes (Manivannan and Srirama chandrasekharan, 2009) . Superior performance of poultry manure might be due to the fact that it can supply the nutrients in soluble form for a quite longer period by not allowing the entire soluble form into solution to come in contact with the soil and other inorganic constituents, thereby, minimizing the fixation and precipitation leading to better yield. This falls in line with the findings of Datta et al. (1994) and Channabasavanna (2002).

Nutrient uptake
There existed significant differences in nitrogen uptake by plant at 30, 60, 90 DAT and at maturity due to different treatments of organic manures (Table 1 and 2). The higher N,P and K uptake by rice crop was obtained with the application of recommended dose of chemical fertilisers which was significantly superior to 100% RDN through poultry manure (T2) at 30 DAT but on par at 60 DAT and both the treatments recorded marked higher uptake than the other treatments. At 90 DAT and at maturity, significantly higher N, P and K uptake by rice crop were observed with T1, which was on par with 50% RDN as basal+ 50% at 10 days before PI stage through poultry manure (T6) and T6 was on a par with 100% RDN through poultry manure (T2) and significantly superior to all other treatments.
Higher NPK uptake with recommended dose of chemical fertiliser compared to other levels of nitrogen in organic form at all crop growth stages could be ascribed to the increase in the available nitrogen due to readily soluble nature of nutrients which might have increased the absorption (Khanda and Dixit, 1996;Biswas and Narayanasamy, 1998).
Increased rice yield could also be attributed to significant increase in nutrient uptake of rice in respective treatment involving organic manure viz., poultry manure and vermicompost. Increase in nutrient availability in poultry manure treated plots was due to higher N content and its gradual mineralisation process. This process ensures increased N availability throughout crop growth, besides improving crop yield. The added organic manure (poultry manure and vermicompost) might have enhanced the activity of beneficial soil microflora increasing the availability and uptake of nutrients by the crop. Further, it has a favorable effect on uptake of N, P and K by rice with poultry manure application as reported by Dravid and Biswas (1996), Hossan et al. (2010) and Meena et al. (2010).
From the present study, it can be concluded that drymatter accumulation and N, P and K uptake at 30, 60, 90 DAT and maturity were significantly influenced by time of application and sources of organic nitrogen. Significantly higher drymatter accumulation and NPK uptake were recorded with recommended dose of fertilizers, which was on a par with 50% RDN as basal + 50% at 10 days before PI stage through poultry manure (T6).