impact of farmers' organic farming practices on soil properties in ...

vital macronutrients such as N, P, K, Ca, Mg and micronutrients such as Fe, Zn, Cu, Mn and
Mo.
Das and Patra (1979) observed that vermicompost contained 0.47 per cent N. Kale et
al. (1992) opined that vermicompost was like any other <strong>organic</strong> manure depending on the
nature <strong>of</strong> wastes used as feed for worms. The nitrogen content varied between 0.5 to 1.2 per
cent. Similar variation in respect <strong>of</strong> phosphorus and potassium content have also been
reported. The chemical analysis <strong>of</strong> vermicompost prepared at University <strong>of</strong> Agricultural
Sciences, Dharwad revealed that it contained 0.8, 1.1 and 0.5 per cent <strong>of</strong> N, P2O5 and K2O,
respectively (Giraddi, 1993). In comparison to FYM, vermicompost contained nearly two
times more N, five times more phosphorus and almost equal amount <strong>of</strong> potassium.
2.1.3 Crop residue
The recycling <strong>of</strong> various forms <strong>of</strong> residue has the advantage <strong>of</strong> converting surplus
farm waste into useful product for meeting the nutrient requirement <strong>of</strong> crops besides
maintaining the soil health and improving the overall ecological balances.
Crop residue management considers the use <strong>of</strong> residue from previous crop as an
input resource and with appropriate management <strong>practices</strong> (Schertz and Bushnell, 1993).
On an average, cereal straw and residue contained about 0.5:0.6:1.5 per cent <strong>of</strong>
N:P2O5:K2O, respectively. The nutrient potential <strong>of</strong> straw (236 million tonnes) from five crops
viz., rice, wheat, sorghum, pearl millet and maize was 1.31, 1.41 and 3.54 million tonnes <strong>of</strong> N,
P2O5 and K2O, respectively (Gaur et al., 1995). Burning <strong>of</strong> crop residues increased the
potential loss <strong>of</strong> N, C, S and possibly some other nutrients due to volatilization and resulted in
unfavourable soil condition (Biederbeck et al., 1980). Hence, its management ensured the
recycling <strong>of</strong> major portion <strong>of</strong> nutrients and exerted considerable influence on crop
performance, primarily through their <strong>impact</strong> on properties <strong>of</strong> soil.
2.1.4 Green manures
Use <strong>of</strong> legumes as green manures contribute to the fertility <strong>of</strong> soil by way <strong>of</strong> addition
<strong>of</strong> roots, nodules, leaves, tops etc. Green manuring is a possibility and a practice in subtropical
regions, where winter fallow is common, which found to substitute nearly 50 to 56 kg
N per ha (Millhotton and Melville, 1991 and Beaver et al., 1993) apart from increasing soil
<strong>organic</strong> matter. It is felt that legumes as winter cover are environmentally desirable which
supply adequate N for cotton production. In situ green manuring, as legume intercrops is
possible under all conditions and results are also encouraging. Intercropping <strong>of</strong> legumes viz.,
sunnhemp, horsegram, cowpea for incorporation as green manure at Coimbatore helped to
reduce N requirement <strong>of</strong> cotton to an extent <strong>of</strong> 35 to 50 per cent (Anon., 1991).
Cowpea as a green manure provided about 800 to 850 kg dry matter with 2.3 to 2.5
per cent N and 0.24 to 0.26 per cent P at 40 DAS. This material was easily decomposable
and contributed 10 to 12 kg N per ha (Tarhalkar et al., 1996).
Dhaincha gave 3500 to 4000 kg <strong>of</strong> dry matter per ha with 2.5 to 2.6 per cent <strong>of</strong> N,
0.20 to 0.22 per cent P2O5 and 1.9 to 2.0 per cent K2O. Its fast decomposing leaves provide N
during the crucial boll development period <strong>of</strong> cotton, while the stalk acts as temporary <strong>organic</strong>
mulch (Tarhalkar et al., 1996).
The sunnhemp used by Badanur et al. (1990) for a field trial contained 2.30, 0.51 and
0.79 per cent <strong>of</strong> N, P2O5 and K2O, respectively.
2.2 EFFECT OF ORGANIC MANURES ON SOIL PHYSICAL
PROPERTIES
2.2.1 Bulk density
Srikanth et al. (2000) found a significant decrease in bulk density (1.27 – 1.18 g/cc) <strong>of</strong>
soil after harvest <strong>of</strong> second crop in the soil amended with compost compared to the in<strong>organic</strong>
fertilizers applied soil.