MSc

The investigation entitled “Crop productivity and weed dynamics in rice based
farming systems” was undertaken with the objective of studying the performance and
weed dynamics of different cropping sequences in rice based integrated farming
systems. The experiment forms a part of ongoing All India Coordinated Research
Project on Integrated Farming System and was carried out in the Integrated Farming
System Research Station (IFSRS), Karamana, Kerala Agricultural University.
The experiment was laid out in randomized block design with seven treatments,
replicated thrice, during the summer and Virippu seasons 2016. The treatments were,
T1 (rice-rice-fallow), T2 (rice-rice-amaranthus), T3 (rice-rice-culinary melon), T4 (rice-
rice-fodder cowpea), T5 (rice+fish)-(rice+fish)-(amaranthus+fish), T6 (rice+fish)-
(rice+fish)- (culinary melon+fish) and T7 (rice+fish)-(rice+fish)-(fodder cowpea+fish).
The varieties of rice, amarathus, culinary melon and fodder cowpea used were Uma,
Arun, Vellayani local and Aiswarya respectively. In treatments T5-T7 fish species viz.,
catla (Catla catla) and rohu (Labio rohita) were introduced into the trenches of 6m x
3m x 1m after transplanting of Virippu crop and were harvested after summer crop.
The data related to rice yield during Virippu and Mundakan season of 2015, generated
from the ongoing trial, were used for working out the economics of the systems.
During summer, growth of amaranthus and fodder cowpea was superior when
grown along with fish. The highest yield of fodder cowpea was obtained when it was
grown as sole crop (T4) followed by culinary melon grown with fish (T6) and fodder
cowpea grown with fish. However, significantly higher rice equivalent yield (REY)
was obtained when culinary melon was integrated with fish (T6).
During summer, among weeds, grasses dominated, followed by sedges and
broad leaved weeds. Population of Echinochloa colona, Lindernia grandiflora and
Fimbristylis miliacea predominated among the grasses, broad leaved weeds and sedges
respectively. The absolute density of different weeds was significantly less in T6 at all
the stages, whereas in T2 and T5 the population was higher. The highest dry weight of
grasses, broad leaved and sedges were in T1 at all stages. Among the other treatments,
T2 recorded significantly higher dry matter of grasses at both the stages. But dry weight
of broad leaved weeds and sedges was significantly higher in T2 and T4 only at 20 DAS.
The weed control efficiency (WCE) of grasses and sedges were significantly higher in
T6 at all stages, while in broad leaved weeds, WCE was similar in all treatments except
T2. In general, among the treatments except T1 removal of all major nutrients (N, P and
K) by weeds was significantly higher in T2, T3 and T5 both at 20 and 40 DAS.
During Virippu, rice plants were taller when grown with fish (T5, T6, and T7)
and in the system where culinary melon sole crop preceded the rice crop (T3) during
summer. Significantly more number of tillers was produced in T6 at 20 DAT and in T7
at 40 DAT. The number of productive tillers m-2 and thousand grain weight did not
vary significantly among treatments. However, significantly higher grain weight
panicle-1 was recorded in T7 (4.08 g), which was on par with T6 T5 and T1. Grain
productivity was significantly higher and on par in the systems in which rice was
integrated with fish (T5, T6, and T7). In general, yield attributes and productivity of rice
were less in rice-rice-fallow system.
During Virippu, season also grasses were dominated followed by sedges and
broad leaved weeds.The highest absolute density of grasses was in T5 at 20 DAT, broad
leaved weeds in T1 and T5 and sedges in T7 and T5 at 20 and 40 DAT. Weed dry weight
of grasses was initially the highest in rice-rice-fallow (T1). At 40 DAT dry weight of
grasses was the highest in T7 and comparable with T6 and T1. Weed dry weight of broad
leaved weeds was the highest in T1 at 20 and 40 DAT and in T5 at 60 DAT. Weed dry
weight of sedges was more in T1 at 20 DAT. The WCE of grasses was the highest in
T3, T1 and T6 at 20, 40 and 60 DAT respectively, while that of broad leaved weeds the
highest in T3 at 20 and 40 DAT and of sedges in T1 at all the stages. Significantly higher
amount of nitrogen was removed by weeds in T1 at 20 DAT, while at 40 and 60 DAT,
it was more in T7. A similar trend was observed in phosphorus and potassium also.
Regarding soil nutrient status before summer, nitrogen content was higher in
T2, while phosphorus and potassium was higher in T5. After the summer crop, nitrogen
content was significantly higher in T2, T3, T5 and T4 which were on par. Phosphorus
and potassium content was significantly higher in T5 and T2 and they were on par. After
the Virippu rice crop, significantly higher available nitrogen content was in T5, T2, T6
and T7 which were on par.
The economic parameters viz., gross returns, net returns, B: C ratio, LRI (Link
Relative index), system profitability and crop profitability were significantly higher in
T6. The contribution of the fish component to the gross income varied from ₹ 1.27 to
1.32 lakhs from 0.50 ha.
From the study, the investigations on weed dynamics revealed that the
population of weeds was more in summer than in Virippu. During summer and Virippu,
grasses dominated followed by sedges and broad leaved weeds, but broad leaved weeds
were more in Virippu than in summer. In summer, weeds were more in fallow and in
systems with sole crops. Among crops, weed growth was more in amaranthus. In
Virippu, weeds were higher in the systems where rice was grown with fish. The
productivity of summer crops and Virippu rice crop was more in cropping sequences
integrated with fish. Rice+fish – rice+fish –culinary melon+fish system performed
better in terms of weed control, yield and profit. This was followed by Rice+fish –
rice+fish – amaranthus+fish system