Effect of preceding summer forage crops and phosphogypsum-enriched urea on productivity and quality of aromatic rice
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Date
2009
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Abstract
A field experiment was conducted during summer-kharif (April-November) seasons of 2007 and
2008 at the research farm of the Indian Agricultural Research Institute, New Delhi, to study the
effect of preceding summer forage crops and phosphogypsum-enriched urea on productivity and
quality of aromatic rice. The experimental soil was sandy clay loam having pH of 7.5, organic
carbon content 0.54%, available N 140.8 kg/ha, available P 17.0 kg/ha, available K 276.0 kg/ha
and available S 11.5 mg/kg soil. The experiment was carried out with 4 treatments during
summer seasons in main plot viz. sole pearlmillet, sole cowpea, pearlmillet + cowpea mixture
and fallow and their residual effect along with 5 phosphogypsum-enriched urea (PGEU) levels in
sub-plots viz. absolute control, 0, 2.5, 5 and 7.5% in split plot design with 3 replication in
succeeding aromatic rice.
Different treatments of preceding summer forage crops and PGEU levels i.e. absolute
control, 0, 2.5, 5 and 7.5% had significant effect on growth parameters viz. plant height, number
of tillers/hill at 30, 60, and 90 DAT. Most of the yield attributes of aromatic rice viz. panicle
length, panicle weight (g), filled grains/panicle and grain weight/panicle were influenced
significantly due to preceding summer forage crops and various levels of PGEU. Significantly
higher grain, straw and biological yield as well as harvest index of aromatic rice was recorded
when it was grown after the harvest of preceding summer forage sole cowpea crop and 7.5%
PGEU. Various preceding summer forage crops had significant effect on nutrients concentrations
viz. N, P, K, S, Zn, Mn, Cu and Fe in aromatic rice grain and straw. Similar trends were also
recorded with their uptake in rice grain, straw as well as total (kg/ha or g/ha). Soil chemical
fertility parameters viz. organic carbon content (%), available major and secondary nutrients viz.
N, P, K, S (kg/ha) and available micronutrients like Zn, Mn, Cu, and Fe (mg/kg soil) after
harvest of aromatic rice in soil also influenced significantly due to summer forage crops and
PGEU treatments. The estimated values viz. partial factor productivity (kg grain/kg N),
agronomic efficiency (kg grain/kg N applied), physiological efficiency (kg grain/kg N uptake),
crop recovery efficiency (%) and N harvest index (%) of applied N were significantly affected
due to summer forage crops and PGEU levels of aromatic rice. Some significant interaction
effects between summer forage crops and PGEU were also recorded such as with dry matter
accumulation (g/hill), number of effective tillers, panicle length, panicle weight, N
concentrations and protein content in rice grain, and Mn concentrations in rice straw.
Physical grain quality parameters viz. hulling (%) and milling (%) increased significantly
due to preceding summer forage crops and the values for these two parameters were higher when
aromatic rice was grown after the harvest of summer forage sole cowpea compared to rest of the
treatments during both the years of study. The significantly higher values of hulling (%), milling
(%) and head rice recovery (%) were recorded with 7.5% PGEU during 2007 and 2008. Some of
the important grain cooking quality parameters of aromatic rice viz. rice grain length before
cooking and after cooking during both the years and rice grain length expansion ratio was
significantly influenced due to preceding summer forage crops. However, significantly higher
values of these cooking quality parameters were recorded with 7.5% PGEU and remained
statistically on par with 5% PGEU during 2007 and 2008. Amylose and protein contents in
aromatic rice grain was significantly influenced due to different summer forage crops and the
values for both these quality parameters were recorded significantly higher when aromatic rice
was either grown after the harvest of sole cowpea or pearlmillet + cowpea mixture compared to
sole pearlmillet or fallow treatments. The PGEU had significant effect on amylose and protein
contents of aromatic rice grain and significantly higher amylose and protein contents in aromatic
rice grain was recorded with 7.5% PGEU during both the years of study.
The significantly higher gross returns and net returns were recorded in summer forage
pearlmillet + cowpea mixture - aromatic rice cropping sequence compared to other summer
forage crops - aromatic rice cropping sequences and fallow - aromatic rice cropping sequence.
The different PGEU had significant effect on the economics of summer forage crops - aromatic
rice cropping sequence. The significantly higher values of gross returns, net returns and B:C ratio
was recorded with 7.5% PGEU during 2007 and 2008 of the study.
Based on the above-mentioned findings it may be concluded that growing of preceding
summer forage crops either sole cowpea or pearlmillet + cowpea mixture - aromatic rice
cropping sequence and application of 5 or 7.5% PGEU would be sufficient to sustain the
productivity and quality of aromatic rice and also to maintain the soil fertility under north Indian
conditions.
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