READING UNIVERSITY NAME: Joe Curtis MODULE: Agro- Environ. Systems Submission date: 22/10/2010 Semester: Fall 2010 Title: How soil management can affect soil quality Introduction Three Labs 1, 2 & 3, compared three agricultural fields with different soil management histories, trying to find out how these different soil managements affected the measured soil parameters. The three different soil management histories are given below: a. Corn field: tilled every year after corn harvest and left bare all winter.
In the spring, it is tilled and cultivated and then planted with corn.It is irrigated all summer and in the fall, if needed. Herbicides are used to control weeds and pesticides for pest control. b. Agrocenter, tilled field: tilled every year after the end of summer and planted with winter crops. In the spring, it is tilled again and cultivated and planted with summer crops.
It is irrigated only during the summer. In the fall, there was no irrigation. Weeds were managed manually during the summer, and were left without management in the fall. The field had been tilled and plant residue was incorporated in the soil two weeks before soil sampling.It was managed organically, without pesticide applications. c.
Agrocenter, non-tilled field: Same management as b, but it was still covered with dense plant growth when we sampled it. Materials & Methods needed Materials * 18 Cylindrical core samplers, of 5-cm diameter and 5-cm height * Knife or spatula * 18 Soil samples ( 3 x 2 samples from 3 different field and 3 different depths ( 5, 10 and 15 cm) * Top loading balance * PH tester instrument (glass electrodes). * EC tester instrument (Electrical Conductivity). * Oven to dry the core samples at 105 0CMethods Laboratory methods have been employed to measure soil parameters such as: Bulk density (g/cm3): The dry weight of soil divided by its volume, working an indicator of soil compaction.
Soil moisture (%): The percent of water volume contained in equal volume of soil core. Soil porosity (%): The percent of the soil core taken up by pores in the soil. Water filled pore space (%): The percent of soil pore space covered by soil moisture.
Soil PH: The value showing the acidity or alkalinity of the soil, affecting biological and nutrient availability.Soil EC: The value showing the water-soluble salts accumulation in the soil, affecting Plant growth, microbial activity, and salt tolerance Each Lab measured and recorded for each field, the above soil parameters values. Then all three Labs shared the findings to each other to calculate the mean and the standard deviation values, for each parameter, for each field. The results from the experimental data are displayed in attached Excel tables for discussion, addressing how the different soil management histories affect the measured soil parameters.In the same Excel Tables, Statistical standard deviation (SD+-) and % Relative Standard Deviation (RSD) have been calculated to check the significance of the results. Mean of all parameter values are shown in respective Graphics.
Each Lab followed the below procedure steps: 1. We took 3 x 2 soil samples from 3 different agroecosystems (Corn field, Agrocenter, non-tilled field, Agrocenter-tilled field) with different management histories, using 18 core samplers. 2. We weighed and labeled each core. 3. We determined the volume in cubic centimeters of each core ? *r2 (core internal radius r=2. cm) 4.
We collected core samples at three sites of the top 15 cm soil layer, taking properly 6 samples using the 5 cm height cores. 5. We weighed the cores with their soil.
6. We put the cores in the drying oven at 105 0C for 24 hours. 7. We recorded : * The mass of each empty core (a) * The mass of each core with the moist soil (b) * And the mass of each core with its dry soil (c) 8.
We calculated the Bulk Density (BD) and soil moisture content of the soil. * Bulk Density (gcm-3): It has been calculated using the following folmula:Weight of oven-dry soil in grams [(c) – (a)] BD (gcm-3) =———————————————————– Volume of core in cm3 * Soil Moisture Content (volume %): As the weight of 1 gram of water is equal to 1 cm3, we calculated the percent of moisture by volume, using the following formula: Volume of soil moisture in cm3 Soil moisture (volume %) = —————————————— x 100% Volume of core in cm3 . We calculated the Soil porosity, which is the percent of the core taken up by pores in the soil. Calculation was based on the ratio of soil Bulk Density (BG) to soil Particles Density (PD). The soil particles have a more or less fixed density of 2. 65 gcm-3. * % Soil porosity: It was calculated using the following formula: % Soil porosity = [1 – (BD / PD)] x 100% 10. We calculated the % Water Filled Pore Space (WFPS), using the % soil porosity and volume % water values.
This is a parameter showing, how much of the pore space is filled with water. * % Water Filled Pore Space (WFPS): It was calculated using the following formula: Volume % moisture % WFPS = ——————————– x 100% % Soil porosity 11. We measured the soil samples PH, using a Kelway PH tester (glass electrodes).
12. We measured the soil samples Salinity, by instrument measuring the Electrical Conductivity-EC (mmho/cm=dS/m). Soils with high concentration (EC> 4 dS/m) of neutral salts are called saline.Results and Discussion Table 1: Mean, Standard Deviation and Relative Standard Deviation of Lab results Field| Lab| Cores| Core mass (g)=c| Core + moist soil mass (g)=b| Core + oven dry soil mass (g)=a| Water lost mass (g)(b-a)| Dry soil mass (g)(a-c)| Bulkdensity g/cm3| Gravimetric water content GWC(c-a)/(c-a)| Volumetric water content VWC(cm3/cm3)| % Soil Porosity| PH| EC| % Water Filled Pore Space WFPS| Corn| | | | | | | | | | | | | | |Mean| | | 96,12| 226,12| 199,77| 26,35| 103,64| 1,05| 0,25| 0,27| 60,16| 7,05| 1,75| 45,36| SD +-| | | 0,28| 17,7| 13,54| 5,28| 13,63| 0,14| 0,03| 0,05| 5,24| 0,46| 0,87| 12,33| RSD%| | | 0,29| 7,83| 6,78| 20,03| 13,16| 13,16| 13,45| 20,03| 8,71| 6,60| 49,6| 27,19| Non-tilled| | | | | | | | | | | | | | | Mean| | | 96,58| 217,02| 195,2| 21,82| 98,62| 1,00| 0,22| 0,22| 62,09| 7| 0,71| 35,99| SD +-| | | 1,59| 10,66| 8,74| 2,86| 8,22| 0,08| 0,02| 0,03| 3,16| 0,18| 0,06| 5,92| RSD%| | | 1,65| 4,91| 4,48| 13,14| 8,34| 8,34| 9,05| 13,14| 5,09| 2,61| 8,68| 16,46| Tilled| | | | | | | | | | | | | | |Mean| | | 95,75| 206,35| 188,18| 18,17| 92,43| 0,94| 0,19| 0,18| 64,47| 6,97| 0,60| 28,8| SD +-| | | 0,36| 8,3| 67,34| 3,31| 6,08| 0,06| 0,03| 0,03| 2,34| 0,27| 0,03| 9,61| RSD%| | | 0,38| 4,02| 35,79| 18,21| 6,58| 6,58| 16,21| 18,21| 3,62| 3,95| 4,96| 33,36| Results: Detailed results have been recorded in the attached Excel Tables (Sheet1 & Sheet2). 1. Corn field findings: * Bulk density (g/cm3): Mean 1. 05 +- 0.
14. RSD % 13. 16 < 20% (no error significance). * Water lost mass (g): Mean 26. 35 +- 5. 28. RSD % 20. 3 (limit no error significance).
* Soil porosity (%): Mean 60. 16 +- 5. 24.
RSD % 8. 71 < 20% (no error significance). * PH : Mean 7.
05 +- 0. 46. RSD % 6. 60 < 20% (no error significance). * EC: Mean 1. 75 +- 0. 87. RSD % 49.
6 >20% (error significance, due to wrong measurement). 2. Non-tilled field findings: * Bulk density (g/cm3): Mean 1. 00 +- 0.
08. RSD % 8. 34 < 20% (no error significance).
* Water lost mass (g): Mean 21. 82 +- 2. 86. RSD % 13. 84 (no error significance). * Soil porosity (%): Mean 62. 9 +- 3. 16.
RSD % 5. 09 < 20% (no error significance). * PH : Mean 7. 00 +- 0. 18. RSD % 2.
61 < 20% (no error significance). * EC: Mean 0. 71 +- 0. 06. RSD % 8. 68 < 20% (no error significance).
3. Tilled field findings: * Bulk density (g/cm3): Mean 0. 94 +- 0. 06. RSD % 6.
58 < 20% (no error significance). * Water lost mass (g): Mean 18. 17 +- 3.
31. RSD % 18. 21 (no error significance). * Soil porosity (%): Mean 64.
47 +- 2. 34. RSD % 3. 62 < 20% (no error significance).
* PH : Mean 6. 97 +- 0. 27. RSD % 3.
5 < 20% (no error significance). * EC: Mean 0. 60 +- 0. 03. RSD % 4. 96 < 20% (no error significance).
The values of measured parameters fall almost within accepted normal limits in all three fields. Discussion The results show that measured soil parameters differ in the three different field origin soil samples, but do not show significant differences. Nevertheless, taking in consideration each field management history we can compare their soil quality. Corn field belongs to long term monoculture, conventionally treated tilled soil.Corn is a highly demanding crop in nutrients, contributing to soil nutrients losses. Agrocenter, tilled field belongs to multiculture, rotational semi-tilled soil, with surface crop residue. Agrocenter, non-tilled field belongs to multiculture, rotational non-tilled soil, with surface crop residue.
In similar soil map units (soil types), like our case, the different field practices management affect soil quality in following aspects : * No-till and other reduced tillage practices leave residues on the surface and protect the soil from wind and water erosion.Along with crop residue the no-till system increases aggregate stability, organic matter, microbial activity and invertebrates, infiltration, available water holding capacity, cation exchange capacity and the breakdown of pesticides. * No-till cool and wet soils contribute to slower residue decomposition, lower nutrient losses, greater denitrification potential, greater biological activity, diversity finally enhancing soil quality and maintaining productivity. * Reduced tillage soils have higher surface bulk density and penetration resistance. * Crop rotations provide biodiversity to reduce insects, weeds, and disease in no tilled systems. Rotations by cover crops that include grass and legumes are good for erosion control and increase organic matter * Conventional management systems with intensive tillage and low residue crops result in soil erosion. Corn is a highly demanding crop in nutrients and its tillage management affects soil quality seriously.
Conclusion Soil Quality is defined as “The ability of soil to function; to supply plants with adequate nutrients, have good drainage and aeration, promote root growth and biological activity. ” The Key Strategies (USDA, NRCS) for the best Soil Quality Management are: • Enhance organic matter Avoid excessive tillage • Manage pests and nutrients efficiently • Prevent soil compaction • Keep the ground covered • Diversify cropping systems In long term evaluation, we could expect that the soil quality of the three tested fields will be classified as: Agrocenter, Non-tilled soil is better than other two tilled fields. Agrocenter, Tilled soil is better than Corn field one, in sense that the first one is rotational and more covered than the highly demanding corn soil.
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