Nutrients particularly of Macronutrient, Losses in in kg/ha in various soil types of India
The amount of nutrients losses through leaching is not constant but depends on many factors like soil texture ,soil permeability ,type of clay minerals ,5 of macro and micro pores....etc
Here is an assessment method of nutrient balance , how it is to be computed by Roy eta l (2003)
The nutrient balance with five inflows (IN1-IN5) and five outflows (OUT1-OUT5), according to Stoorvogel and Smaling (1990), was used for the calculation.
IN1: Mineral fertilizer input was based on fertilizer use data from 1980. These had to be multiplied by 2.5 for N, 2.0 for P and 3.0 for K, because fertilizer consumption in Kenya had increased considerably. Tea received most N fertilizer, and P fertilizer was applied mainly to maize.
IN2:Survey data for manure application were available. The nutrient contents of the manure were set at 1.3 percent for N, 0.5 percent for P and 1.6 percent for K, based on dry matter. Most manure was applied to coffee and bananas, and came mainly from paddocks and stables.
IN3:Atmospheric deposition was determined using the regression equations from Stoorvogel and Smaling (1990). The nutrient input was linked with the square root of the mean annual precipitation. The regression coefficients for N, P and K were 0.140, 0.023 and 0.092, respectively.
IN4:BNF was the sum of non-symbiotic N fixation and the contribution of beans, the only leguminous species in the study area. Symbiotic N fixation was set at 50 percent of the total N uptake. Non-symbiotic N fixation was determined using the regression equation of Stoorvogel and Smaling (1990):
IN4 = 2 + (P - 1 350) × 0.005
N5:Sedimentation was not relevant in the study area.
OUT1:Production statistics were available and were multiplied by the nutrient content of the crops. This generated the export of nutrients with harvested products. Insufficient information was available to take differences in nutrient use efficiency into account.
OUT2:The export of nutrient with crop residues was calculated by multiplying the amount of residues by the nutrient contents and a removal factor.
OUT3:Leaching of N and K were determined with a transfer function (based on literature). N leaching was calculated as a percentage of the sum of mineral N in the soil (Nmin) and N applied by mineral and organic fertilizer. The percentages were based on rainfall and clay content (Table 13).
Nmin = 20 × Ntot × M
where:
Ntot = total N content of the soil of the upper 20 cm,
M = mineralization rate (2.5 or 3.0 percent).
K leaching was calculated in a similar way with the percentages of Table 13 multiplied by the sum of exchangeable K (in kilograms per hectare) and mineral and organic fertilizer K.
OUT4:For gaseous nitrogen losses, only denitrification was taken into account. A regression function based on an extensive literature research was developed:
OUT4 = (-9.4 + 0.13 × C + 0.01 × P) × (Nmin + Nfert)
where:
C = clay content (percent);
P = mean annual precipitation (mm/year);
Nmin = mineral soil N (kg/ha);
Nfert = mineral and organic fertilizer N.
OUT5:Erosion was calculated using the USLE. Annual soil loss per hectare was estimated as a function of rainfall erosivity (R), soil erodibility (K), slope gradient (S), slope length (L), land cover (C) and land management (P). The R factor was set at 0.25 for the entire district. The K factor was derived from soil texture, organic matter content and permeability. The S and L factors were determined with:
S = (0.43 + 0.30 × s = 0.043× s2)/6.613
L = (d/22.13)0.5
where:
s = slope gradient (percent);
d = slope length (m), set at a fixed value of 100 m.
An average C factor was estimated for each LUT.
The P factor was related with the slope (s): P = 0.2 + 0.03 × s
The soil loss (R × K × S × L × C × P) was multiplied by the nutrient content of the soil and an enrichment factor of 1.5 to obtain the export of nutrients by erosion. For P and K, the net loss was multiplied by 0.75 to compensate for soil formation at the root base.
For year-round fallow, equilibrium conditions were assumed, i.e. IN - OUT = 0.
For further details , please find enclosed the relevant PDF ..
Some studies reported that the application of 150 Kg N/ ha for commercial cultivation lead to 18-20 Kg N loss by leaching only.
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