Yield and Economics of Transplanted Rice as Influenced by Crop Establishment Methods, Weed and Nutrient Management Practices

Field experiments were conducted in clay loam soil of Tamil Nadu Agricultural University, Coimbatore during rabi, 2009 and 2010 to evaluate the different crop establishment methods, weed and nutrient management practices in transplanted rice. The treatments consisted of four crop establishment methods and weed management practices in main plot and four nutrient management practices in sub plot. The results revealed that SRI planting (25 cm x 25 cm) and weeding with two way rotary weeder thrice at weekly interval starting from 15 DAT along with recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) + 12.5 t FYM ha -1 + Azophosmet (seed and soil application) + PPFM (foliar spray) at active tillering, panicle initiation and 50 per cent flowering stage registered higher grain yield and net return. However, B:C ratio was higher with SRI planting and weeding with two way rotary weeder thrice at weekly interval starting from 15 DAT and application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ).

Rice (Oryza sativa L.) is the staple food for nearly 3 billion people and the demand continues to grow as population increases (Carrieger and Vallee, 2007). In India, rice is cultivated round the year in one or the other part of the country, in diverse ecologies spread over 44.6 m ha (Rai, 2004) with a production of 131 m t of rice with average productivity of 3.37 t ha -1 (IRRI, 2011). It is estimated that by 2020 at least 170 to 180 m t (115-120 m t milled rice) of rice is to be produced in India with an average productivity of 4.03 t ha -1 to maintain the present level of self sufficiency (Mishra et al., 2006), which means, the productivity should go up by a tonne from the current level.
Manual transplanting is the most common practice being followed under lowland ecosystem. Nonavailability of irrigation water, shortage of labour during peak period of transplanting and escalating labour cost make transplanting more expensive which invariably leads to delay in transplanting and results in reduction of yield and profit (Gangwar et al., 2008). To mitigate this problem, the System of Rice Intensification (SRI), a revived method of transplanted rice cultivation by exploiting the genetic potential of rice provides a favourable growing environment to increase the productivity and economic returns. Besides, it enhances soil health with reduction in input use such as seeds, water, labour, etc (Gujja and Thiyagarajan, 2009). Hence, the experiment was carried out to evaluate the productivity of transplanted rice under different crop establishment methods, weed and nutrient management practices.

Materials and Methods
Field experiments were conducted at Tamil Nadu Agricultural University, Coimbatore during rabi, 2009 and 2010 to elucidate the effect of crop establishment methods, weed and nutrient management practices on the yield and economics of lowland transplanted rice. The medium duration rice variety CO(R)50 was used as test variety. Soil of the experimental fields was clay loam in texture classified taxonomically as Vertic Ustochrept, low in available nitrogen (202.6-216.0 kg ha -1 ), medium in available phosphorus (12.6-16.1 kg ha -1 ) and high in available potassium (420.4-511.0 kg ha -1 ).
Conventional planting was taken up at 25 cm x 15 cm spacing with 21 days old seedlings obtained from conventional wet nursery. Under SRI, 14 days old seedlings obtained from modified rice mat nursery were transplanted at 25 cm x 25 cm spacing. Rotary weeder weeding was done thrice starting from 15 DAT at weekly interval in one direction under conventional planting (25 cm x 15 cm) and both the directions under SRI planting (25 cm x 25 cm). Hand weeding was done twice at 20 and 40 DAT.
Farm yard manure was applied @ 12.5 t ha -1 uniformly as per the treatment schedule, incorporated and then leveled. Recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) for the medium duration rice variety was followed as per the treatments. Nitrogen was applied in four splits viz., 40 kg ha -1 each at basal, active tillering and panicle initiation stage and 30 kg ha -1 at flowering stage. The entire dose of phosphorus was applied as basal. Potassium was applied in four splits viz., 25 per cent each at basal, active tillering, panicle initiation and flowering stages.
The experimental plots were irrigated to 2 cm depth uniformly in all the treatments after the appearance of hair line cracks, up to panicle initiation stage. After panicle initiation, the plots were irrigated to 5 cm depth on disappearance of ponded water. Irrigation was stopped 15 days prior to harvest.
Data on yield were subjected to an analysis of variance (F-test) as per the methods suggested by Gomez and Gomez (2010). Economics for all the treatments was worked out on the basis of prevailing input cost and market price of grain and straw at the time of experimentation.

Grain yield
Crop establishment methods, weed management and nutrient management practices had significant influence on grain yield (kg ha -1 ) during both the years of experimentation (Table 1). The SRI planting with two way rotary weeder weeding thrice at weekly interval starting from 15 DAT (M4) produced distinctly more grain yield during both the years. However, it was comparable with conventional planting with one way rotary weeder weeding thrice at weekly interval starting from 15 DAT (M2) during both the years. Conventional planting combined with hand weeding at 20 and 40 DAT (M1) recorded lucidly lesser grain yield during both the years. However, comparable grain yield was obtained with M2 and SRI planting combined with  (M1) during rabi 2009 and rabi 2010, respectively. This might be due to less crop weed competition, larger root system and crop canopy and higher microbial population which facilitated the enhanced nutrient uptake, photosynthetic activity and remobilization of photosynthates to grain which resulted in higher yield attributes and yield. This is in accordance with the findings of Hugar et al. (2009) who stated that SRI gave higher grain yield due to large root volume, strong tillers with improved yield attributes. Chandrapala et al. (2010) also reported increased grain yield with SRI which was attributed to lesser competition, enhanced solar radiation interception, nutrients uptake and higher yield attributes.
Combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM and biofertilizers viz., Azophosmet as soil and seed treatment and PPFM as foliar spray (S4) attained its statistical supremacy by recording higher grain yield during both the years. Significantly more grain yield was observed with combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM (S3) than application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) (S2). Distinctly lower grain yield was obtained with absolute control without fertilizer (S1) over all other nutrient management practices during both the years. Higher grain yield in S4 might be attributed to greater root development and activity, higher microbial population and increased nutrient availability throughout the crop growth which resulted in improved yield attributes. This finding is in accordance with the results of Virdia and Mehta (2010) who found that improvement in nutrient supply with organics improved soil physicochemical and biological properties, in turn increased the nutrient availability which ultimately enhanced the grain yield. Further, Belimov et al. (1995) claimed earlier that inoculation of bacterial mixture of N2 fixing and P solubilizing bacteria provided more balanced nutrition for the plants.
Crop establishment methods, weed management and nutrient management practices had significant interaction with each other at all the crop growth stages during both the years. The SRI planting with two way rotary weeder weeding thrice at weekly interval starting from 15 DAT in association with combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM and biofertilizers viz., Azophosmet as soil and seed treatment and PPFM as foliar spray (M4S4) registered higher grain yield during both the years. This might be due to larger canopy with greater root development and activity, less intra plant competition, improved remobilization of assimilates to grain and higher nutrient availability. Whilst, lesser grain yield was recorded under conventional planting combined with hand weeding at 20 and 40 DAT and absolute control without fertilizer (M1S1) during both the years.

Straw yield
Significant difference due to the crop establishment methods and weed management practices was evident only during rabi 2010 (Table 2). SRI planting with two way rotary weeder weeding thrice at weekly interval starting from 15 DAT (M4) resulted in significantly higher straw yield. However, comparable straw yield was observed with conventional planting with one way rotary weeder weeding thrice at weekly interval starting from 15 DAT (M2) with that of M4 due to higher tillers and DMP. Likewise, SRI planting combined with hand weeding at 20 and 40 DAT (M3) registered lesser straw yield which was comparable with conventional planting combined with hand weeding at 20 and 40 DAT (M1). This result is in corroboration with the findings of Revathi (2009) who reported that higher straw yield in SRI due to higher tillers and DMP.
Combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM and biofertilizers viz., Azophosmet as soil and seed treatment and PPFM as foliar spray (S4) recorded higher straw yield during both the years. However, comparable straw yield was noticed with combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM (S3) and application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) (S2). Invariably, lesser straw yield was registered with absolute control without fertilizer (S1) over all other nutrient management practices during both the years. Kumar et al. (2010) also reported that straw yield was higher with application of 100% NPK + 20 t FYM ha -1 + 10 kg ha -1 BGA. Crop establishment methods, weed and nutrient management practices did not exhibit significant interaction effect on straw yield during both the years.

Harvest index
SRI planting with two way rotary weeder weeding thrice at weekly interval starting from 15 DAT (M4) recorded higher harvest index during both the years which could be attributed to better soil aeration provided by rotary weeding and better translocation of photosynthates from vegetative parts to grains (Table  2). However, comparable harvest index was observed with SRI planting combined with hand weeding at 20 and 40 DAT (M3) and conventional planting with one way rotary weeder weeding thrice at weekly interval starting from 15 DAT (M2) during both the years. Whereas, conventional planting combined with hand weeding at 20 and 40 DAT (M1) resulted in lower harvest index than with other planting systems during both the years. However, it was comparable with M2 during rabi 2010.
Combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM and biofertilizers viz., Azophosmet as soil and seed treatment and PPFM as foliar spray (S4) registered higher harvest index during both the years because of the efficient translocation of food assimilates by biofertilizers. However, comparable harvest index was observed with combined application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) along with 12.5 t ha -1 FYM (S3) and absolute control without fertilizer (S1) with that of S4 during both the years. Obviously, application of recommended dose of fertilizer (150:50:50 kg NPK ha -1 ) (S2) recorded lesser harvest index over other nutrient management practices during both the years. However, comparable harvest index was noticed with S1 and S3 during rabi 2010. This result is in conformity with the findings of Kalaiyarasi (2009) who reported that application of scheduled fertilizer pulled down the harvest index compared to no-manure. The negative impact was either reduced or nullified only when farm yard manure and biofertilizers were added to the fertilizer schedule.