Sir, for LLWR calculation you have to take 4 observations

1) BD by core method

2) Moisture content at 0.1 bar (MCfc) and at 15 bar (MCwp) using pressure plate method

3) Moisture content at 10% aeration porosity (MCap) can be calculated as follows:

MCap = MCsat - 10%

where, MCsat is maximum water holding capacity i.e. total pore space of soil (% v/v)

4) Soil water content corresponding to 2MPa soil strength (MC2Mpa) that can be done by taking soil penetration resistance data of respective soil depth using cone penetrometer along with soil moisture (by gravimetric method) at 4-6 days interval during the period from sowing to 1st irrigation and also during the drying cyclc after each irrigation. The above observations can be used to develop a multiple regression equation relating soil penetration to soil moisture, bulk density.

e.g. PR (MPa)= c - a1 X MC + a2 X BD

By putting PR= 2 MPa in this equation you can get the moisture content (MC2MPa)

Finally curves with bulk density on x-axis and MCap, MCwp, MCfc and MC2MPa on y-axis were drawn on the same scale to determine the limits of LLWR as a function of bulk density.

Thank you Bappa for your views.