MSc

A study entitled “Nutrient management for productivity enhancement of
cassava var. Vellayani Hraswa in lowlands” was conducted at College of Agriculture,
Vellayani, Thiruvananthapuram, Kerala to standardize the nutrient management for
productivity enhancement of cassava var. Vellayani Hraswa in lowlands and to work
out the economics of cultivation. The field experiment was conducted at Integrated
Farming System Research Station, Karamana, Thiruvananthapuram from September
2017 to February 2018. The treatments consisted of three sources of organic manure
(m1 - FYM @ 12.5 t ha-1, m2 - FYM @ 6.25 t ha-1 + green manuring in situ and m3 -
poultry manure (PM) @ 2.5 t ha-1 + green manuring in situ), two levels of N (50 and
75 kg ha-1) and two levels of P (25 and 50 kg P2O5 ha-1) along with a uniform dose of
100 kg K2O ha-1. The 3 x 2 x 2 factorial experiment was laid out in randomized block
design with three replications. Organic manures were applied at land preparation as per
the treatments. Cassava var. Vellayani Hraswa was planted on ridges at a spacing of 90
cm x 90 cm after applying 1⁄2 N + full P + 1⁄2 K of the fertilizer dose as per the treatments.
Cowpea @ 30 kg ha-1 was sown on the two sides of the ridges in between cassava
plants for green manuring in situ and was incorporated 50 days after planting along
with top dressing (1⁄2 N + 1⁄2 K) for cassava.
Among the sources of organic manure, PM @ 2.5 t ha-1 + green manuring in
situ produced taller plants with higher branch number, leaf number and leaf area index
(LAI) at 4 months after panting (MAP) and harvest. Application of 75 kg N ha-1
registered taller plants and higher number of branches and LAI at 4 MAP and harvest
and higher leaf number at all the stages. Application of 25 kg P2O5 ha-1 was found
sufficient for improving growth characters.
Application of PM @ 2.5 t ha-1 + green manuring in situ registered the highest
number and weight of tubers plant-1, percentage of productive roots and length and
mean weight of tuber and lower rind to flesh ratio. The yield attributes except rind to
flesh ratio were significantly higher with 75 kg N ha-1. Application of 50 kg P2O5 ha-1
produced higher percentage of productive roots plant-1 and tuber girth while 25 kg P2O5
ha-1 produced higher tuber weight plant-1. The treatment combination m3n2p1 registered
significantly higher tuber weight plant-1.
The tuber yield was significantly and positively correlated with LAI at 4 MAP
and harvest, number and weight of tubers plant-1 and mean tuber weight. Higher tuber
yields were obtained from green manured plots. The highest tuber and top yields were
produced by PM @ 2.5 t ha-1 + green manuring in situ, 75 kg N ha-1 and 25 kg P2O5
ha-1. The treatment combination m3n2p1 recorded the highest tuber yield of 36.22 t
ha-1 and top yield of 10.04 t ha-1. Similar trend was observed in dry matter production.
The practice of green manuring in situ reduced weed infestation in cassava and
improved its growth and yield.
The tubers with the lowest HCN content (38.92 mg kg-1) were produced by
FYM @ 6.25 t ha-1 + green manuring in situ. Nitrogen @ 50 kg ha-1 recorded higher
starch (27.03%) and lower HCN (39.83 mg kg-1) content while 75 kg N ha-1 registered
higher protein content (2.61%).
Application of PM @ 2.5 t ha-1 + green manuring in situ, 75 kg N ha-1 and 25
kg P2O5 ha-1 resulted in the highest N, P and K uptake. Poultry manure @ 2.5 t ha-1 +
green manuring in situ recorded significantly higher pH, organic carbon and available
N, P and K status in the soil after the experiment. Levels of N and P had significant
influence only on available P status in the soil and higher P status was registered by 75
kg N ha-1 and 50 kg P2O5 ha-1.
Higher net income of ₹ 373240 ha-1 and benefit cost ratio of 3.19 could be
obtained from the combined application of PM @ 2.5 t ha-1 + green manuring in situ
along with 75 kg N ha-1 and 25 kg P2O5 ha-1 (m3n2p1). The results indicated
the feasibility of substitution of FYM with PM + green manuring in situ.
The results of the study revealed that higher yield, net income and benefit cost
ratio could be realized from cassava var. Vellayani Hraswa in lowlands by the
application of poultry manure @ 2.5 t ha-1 + green manuring in situ with cowpea + 75
kg N ha-1 + 25 kg P2O5 ha-1 combined with 100 kg K2O ha-1.