Improving soil structure to reduce soil degradation

Transcription

1 Managing soils for profit and restoration Improving soil structure to reduce soil degradation Professor R Jane Rickson Chair in Soil Erosion and Conservation Cranfield Soil and AgriFood Institute February 16 th 2016

2 Outline of the presentation 1. What is soil structure? 2. Soil degradation: cause or effect of poor soil structure? 3. The importance of soil management to improve soil structure 4. Take home messages

3 1. What is soil structure? Soil structure depends on: Mineral content (texture: clays, silts and sands) 45% Chemical composition (bonds between particles) Air 25% Water 25% Organic matter content 5% Soil flora: roots and leaves Soil fauna macro-organisms e.g. earthworms micro-organisms microbes» bacteria» fungi» viruses Organic Matter 5% Water 25% Air 25% Clays, silts and sands 45% The physical arrangement of soil particles, air space, water content and organic matter = soil structure Allows roots to grow Allows movement of air, water and soil organisms Affects soil strength / loading capacity (resist compaction)

4 1. What is soil structure? Soil aggregate size distribution Pore size distribution Macropores (easy drainage a good or bad thing?; poor seed bed; lodging) Mesopores (water storage / holding capacity (floods and droughts), water availability to crops) Micropores (water unavailable to crops; more air and water movement) The 3 Rs : Well structured soils can receive, retain and release water Visual soil assessment / evaluation research.co.nz/publi cations/books/visual -soil-assessmentfield-guide

5 1. What is soil structure?

6 1. What is soil structure? Soil structure and soil health / soil quality ORGANIC MATTER BIOTA WATER/AIR NUTRIENTS STRUCTURE Soil Structure and Soil Health: The pivotal 5 (after Professor Karl Ritz, pers.comm)..but soil structure can be affected by management (good and bad)

7 2. Soil degradation: cause or effect of poor soil structure? As identified in the EU Thematic Strategy for Soil Protection (2006) ORGANIC MATTER BIOTA WATER/AIR NUTRIENTS STRUCTURE Estimated 12 million hectares of agricultural land are lost to soil degradation every year.

8 Soil degradation in the UK: cause or effect of poor soil structure?

9 2. Soil degradation: cause or effect of poor soil structure? Example: Soil erosion in England & Wales Wind erosion Tillage erosion Co-extraction with root crops and farm machinery Water Typical erosion rate range (t ha -1 year -1 ) Land use affected Arable, upland, some pasture Arable Arable Arable, pasture, upland Exported off field Yes No Yes Yes Comparison of the magnitude of soil loss for different erosion processes (Owens et al., 2006). N.B. Rate of soil formation 1 t ha -1 year -1 (Verheijen et al., 2009)

10 2. Soil degradation: cause or effect of poor soil structure? Irreversible loss of a natural resource / asset? e.g. loss of soil depth due to erosion Compaction high bulk density, loss of porosity, flooding? Loss of organic matter / carbon (carbon storage and mitigating climate change) Yield decline (quantity, quality and reliability; e.g. 20 million tonnes of grain per annum) Costs (e.g. nutrient replacement) Off-site consequences (water quality) Courtesy of Alastair Leake True impacts on food production often masked by unsustainable inputs (e.g. irrigation, chemical fertilisers)

11 2. Soil degradation: cause or effect of poor soil structure? million per year (2010) Agricultural production Flooding Ecosystem service Regulating Water quality Provisioning Greenhouse gas emission s Other Cultural Central estimate Erosion ?? % Compaction ?? % Loss of organic matter 2?? ?? % Diffuse contamination???? 25*? 25 2% Loss of soil biota???????? Soil sealing???????? TOTAL ? 1,229 % 20% 19% 11% 49% 2% 100 *cost of regulation to protect soils from contamination? Estimates not available at national scale After Graves, A., Morris, J., Deeks, L.K., Rickson, R.J., Kibblewhite, M.G., Harris, J.A, and Farewell, T.S The Total Costs of Soils Degradation in England and Wales. SP1606. Final Report to Defra, June Total

12 3. The importance of soil management to improve soil structure Aim of soil management: To maintain a fertile seedbed and root zone, whilst retaining maximum resistance to soil degradation ORGANIC MATTER A. Enhance soil and crop productivity (quantity, quality and reliability of marketable yield) Provide physical support to canopy and root development Improve uptake of water and nutrients by roots Reduce soil borne pests / diseases / weeds BIOTA NUTRIENTS WATER STRUCTURE B. Control soil degradation Erosion; diffuse pollution; compaction; losses of C, organic matter and habitats; salinisation; acidification Soil health: the pivotal 5 C. Concept of sustainable intensification Producing more (quantity/ quality/ reliability of marketable yield) with less environmental impact / damage A + B = C Soil erosion, Bedfordshire

13 Soil management practices to improve soil structure: examples 1. Soil cultivation and tillage Maintain soil structure Prepare a suitable growing medium for a crop (germination, emergence and development) Maintain organic matter and soil biology Bury/incorporate surface residues/fym Remove local or general soil compaction problems (promote drainage) Provide adequate soil strength to support surface traffic 2. Crop agronomy + 14 minutes rainfall 3. Increasing soil organic matter content

14 Soil management practices to improve soil structure: examples a) Conventional v conservation tillage reduced tillage, minimum till, strip tillage, zero till, etc. The main reasons to use min-till are: To reduce energy consumption To reduce labour, fuel and machinery costs High work rates To conserve moisture To retain plant cover to minimize erosion Minimise loss of organic matter Keep soil structure / less compaction + 14 minutes rainfall Courtesy of Professor Karl Ritz

15 Soil management practices to improve soil structure: examples a) Conventional v conservation tillage Challenges of min-till Min-till needs dry ground conditions for sowing in order to avoid compaction and smearing in the final seed bed. One of the best tools in your tool box for min-till is patience Wait until conditions are excellent for sowing. Avoid sowing in a compacted or smeared seed bed. Residue management Slugs Machinery Weeds and costs of control (economic and environmental) + 14 minutes rainfall Courtesy of Dr Rob Simmons Courtesy of Professor Karl Ritz

16 Soil management practices to improve soil structure: examples 1. Soil cultivation and tillage b) Timeliness of operations soil moisture content when trafficking erosion and compaction risks? c) Depth of operations plough pan formation? effects on biota? Effects on structure? doubling the working depth, approx. quadruples the drawbar pull force and fuel requirement d) Direction of operations (up/down on steep, marginal land)

17 A case study: Optimising soil disturbance and use of mulches for erosion and runoff control Dr. Joanne Niziolomski

18 Field trial treatments Shallow soil disturbance (175 mm), both with and without straw mulch (6 t ha -1 ). Winged tine Narrow with two shallow leading tines Modified para-plough

19 Total soil loss (kg) Soil disturbance field trial results: Total soil loss (kg) No shallow Non-SSD Narrow NSLT tine shallow Modified MPP Winged WT tine soil disturbance leading tine SSD type para-plough (Niziolomski, 2015) Modified para-plough with straw most reduced soil loss Little significant difference was observed between SSD (different tines) and Non-SSD Straw mulch decreased total soil loss as compared with no mulch

20 Soil management practices to improve soil structure: examples 2. Use of crop agronomy for better soil management Rotations Cover and companion cropping Break crops (deep rooting species) Nutrient replenishment (e.g. N fixing legumes) Grass waterways (erosion and runoff control) N.B. Demonstrates Good Agricultural and Environmental condition (GAEC) Eligible for Basic Payment Scheme under CAP reform and greening rules

21 Root morphology of cover crops T D F E Turnip Rape Root Root traits expected to Crop Type improve soil structure Wheat D Fibrous vigorous deep roots Rye D Deep fibrous roots Oats D Aggressive deep roots Italian ryegrass F Fibrous root system Lucerne E Deep and aggressive rooting Phacelia F Prolific root system but more confined to surface Radish Mustard Fodder radish Chicory T Tap root Sweet clover T E Tap root, long and extensive root hairs on laterals Vigorous and extensive multi-order lateral branching, Field bean E Large, strong roots Lupin E Tap root Cranfield University PhD study (Agnese Mancini): Cover crops for soil erosion and runoff control in forage maize

22 Case study: Use of grassed waterways for sediment control

23 Case study: Use of grassed waterways for sediment control

24 Soil management practices for healthy soils 3. Increasing soil organic matter content Green manures (cover cropping) Composts Mulches Sewage sludge Digestate from AD plants Increase organic matter content, carbon, soil biota Improve soils structure and resilience Effects will be specific to materials used and sites (weather, soil type, etc) Closed-Loop

25 Case study: Application of organic waste to restore soil health and productivity of a degraded soil Benedict Unagwu Improve Soil Quality Indicators (SQIs)? Increase crop yield? Mushroom compost Poultry manure Anaerobic digestate PAS compost (green waste)

26 Results: Post-incubation soil analysis (Organic Matter Content) F(17,62) = , p = Key: C = Control; PM = Poultry manure; OM (%) PAS = PAS 100:2005 Quality Protocol compliant compost; SW = Anaerobic digestate solid waste; MC = Mushroom compost; = 10 t ha; 2 = 30 t/ha. 0.0 CF CNF PM1F PM1NF PM2F PM2NF PAS1F PAS1NF PAS2F PAS2NF SW1F Treatments SW1NF SW2F SW2NF MC1F MC1NF MC2F MC2NF F = with fertiliser; NF = without fertiliser Mean Mean±SE

27 Amendment effects on maize height and biomass control 10 t ha -1 PM 10 t ha -1 MC At 3 weeks after planting At tasseling (9 weeks after planting) 27

28 4. Take home messages Soil structure is fundamental to healthy soils ORGANIC MATTER Soil management can improve soil structure, increase crop productivity and control degradation processes Cost effectiveness of practices will be site specific and must fit into current farming practices socio-economic context infrastructure / machinery farmer psychology / behaviour Ultimate goal is economically, socially and environmentally acceptable food production = sustainable intensification BIOTA NUTRIENTS STRUCTURE WATER

29 In conclusion.. The challenge for global agriculture is to grow more food, on not much more land, using less water, fertiliser and pesticides than we have historically done. Sir John Beddington former UK Government Chief Scientific Adviser. The answer is in the soil Thank you for your attention Professor Jane Rickson ext. 2705