Agricultural sampling system and related methods
An automated computer-controlled sampling system and related methods for collecting, processing, and analyzing agricultural samples for various chemical properties such as plant available nutrients. The sampling system allows multiple samples to be processed and analyzed for different analytes or chemical properties in a simultaneous concurrent or semi-concurrent manner. Advantageously, the system can process soil samples in the “as collected” condition without drying or grinding. The system generally includes a sample preparation sub-system which receives soil samples collected by a probe collection sub-system and produces a slurry (e.g., mixture of soil, vegetation, and/or manure and water), and a chemical analysis sub-system which processes the prepared slurry samples for quantifying multiple analytes and/or chemical properties of the sample. The preparation sub-system may comprise a slurry recirculation flow loop configured with devices to stir, measure, and adjust a water to solids ratio of the slurry.
1 . A method for forming and processing an agricultural slurry, the method comprising:
adding water and agricultural solids to a mixing chamber of a mixing device;
agitating the water and agricultural solids at a first speed with a rotatable first blade mechanism of the mixing device to form a slurry;
discharging the slurry from the mixing device into a coarse filter unit via a flow conduit fluidly coupled therebetween;
coarsely filtering the slurry through a filter screen of the coarse filter unit to remove particles in the slurry larger than a predetermined first maximum particle size;
receiving the filtered slurry from the coarse filter unit in a stirring chamber of a stirring device defining the stirring chamber; and
agitating the slurry with a rotatable second blade mechanism at a second speed different than the first speed in the stirring device;
wherein the stirring chamber of the stirring device forms an integral part of a closed slurry recirculation flow loop fluidly coupled to the coarse filter unit, the slurry recirculation flow loop comprising a slurry recirculation pump which circulates the slurry through the slurry recirculation flow loop and the stirring device, the slurry recirculation flow loop being fluidly isolated from the mixing device when the slurry is circulating through the slurry recirculation flow loop.
2 . The method according to claim 1 , wherein the first speed is faster than the second speed.
3 . The method according to claim 1 , wherein the stirring device is operable to maintain the slurry in a mixed homogenous state as the slurry circulates through the slurry recirculation flow loop.
4 . The method according to claim 3 , further comprising measuring a density of the slurry in the mixed homogenous state concurrently with circulating the slurry through the slurry recirculation flow loop.
5 . The method according to claim 4 , wherein the slurry recirculation flow loop comprises a density measurement device which measures the density of the slurry, the density measurement device being a U-tube vibrational density meter configured to measure slurry in a dynamic flowing state through the meter or a stagnant flow state.
6 . The method according to claim 1 , wherein the slurry recirculation flow loop is fluidly coupled to a slurry chemical analysis sub-system configured to analyze the slurry for an analyte of agricultural-related significance.
7 . The method according to claim 6 , further comprising finely filtering the slurry through a fine filter unit fluidly disposed within the slurry recirculation flow loop before a step of flowing filtered slurry from the fine filter unit to the slurry chemical analysis sub-system, the fine filter unit being configured to remove solid particle in the slurry having a predetermined second maximum particle size smaller than the predetermined first maximum particle size of the coarse filter unit.
8 . The method according to claim 1 , further comprising pressurizing the flow conduit with air between the mixing device and stirring device to drive the slurry through the coarse filter unit and into the stirring device.
9 . The method according to claim 8 , wherein the mixing device is fluidly isolated from the flow conduit during the pressurizing step.
10 . The method according to claim 1 , further comprising injecting pressurized air and water forming an aerated stream through the coarse filter unit during the coarsely filtering step to prevent solid particles larger than the predetermined first maximum particle size from blocking the filter screen.
11 . The method according to claim 10 , wherein the coarsely filtering step comprises flowing the slurry in a first direction through the filter screen and flowing the aerated stream through the filter screen in a second direction opposite to the first direction.
12 . The method according to claim 11 , wherein the slurry enters a first cavity in the coarse filter unit on a first side of the filter screen and the pressurized air and water are injected into a second cavity in the filter unit on a second side of the screen opposite the first side.
13 . The method according to claim 12 , wherein the coarse filter unit comprises a slurry inlet configured to flow the slurry in a linear flow path through the first cavity, a waste outlet configured to discharge the oversized particles from the first cavity in the same linear flow path, and a slurry outlet configured to discharge the filtered slurry in a direction transverse to the linear flow path.
14 . The method according to claim 1 , wherein the slurry recirculation flow loop further comprises an accumulator positioned upstream of the slurry pump, the accumulator configured to dampen pressure surges in the slurry recirculation flow loop.
15 . The method according to claim 1 , wherein the slurry recirculation flow loop is downstream of the mixing device and the coarse filter unit.
16 . A method for forming and processing an agricultural slurry, the method comprising:
adding water and agricultural solids to a mixing chamber of a mixing device;
agitating the water and agricultural solids at a first rotational speed with the mixing device to form a slurry;
discharging the slurry from the mixing device and receiving the filtered slurry in a stirring chamber of a stirring device; and
agitating the slurry at a second rotational speed different than the first rotational speed in the stirring device;
wherein the stirring chamber of the stirring device forms an integral part of a closed slurry recirculation flow loop, the slurry recirculation flow loop comprising a slurry recirculation pump which circulates the slurry through the slurry recirculation flow loop and the stirring device, the slurry recirculation flow loop being fluidly isolated from the mixing device when the slurry is circulating through the slurry recirculation flow loop.
17 . The method according to claim 16 , wherein the slurry recirculation flow loop is downstream of the mixing device.