Benefits of NT over CT. Water conservation in the NT benefits from reduced ET and runoff, and increased infiltration.

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Samuel McDaniel
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2 Benefits of NT over CT Water conservation in the NT benefits from reduced ET and runoff, and increased infiltration.

3 Weed control. Increased water and root penetration Uniform stands. Typically 4 to 8 rounds of tillage operations potential for heavy wind and water erosion of soil, and soil and Water quality deterioration. Reduction in tillage is inevitable for SUSTAINABILITY.

Hipped, Subsoiled, Rehipped after harvest NT : None Planting : In March; Harvest at Maturity in August N : ~224

4 CT vs. NT Experiment Field size : 200 X 35 m (0.65 ha) Established in 2008 Soil: Dundee silt loam Tillage : Conventional tillage(ct), No Tillage (NT) CT : Hipped, Subsoiled, Rehipped after harvest NT : None Planting : In March; Harvest at Maturity in August N : ~224 kg/ha Cultivar: : P31 G71 LL RR : P33 N55 RR : P33 N58 RR LL 2016 : DKC66-97 Irrigations : 2-3 cm, 1 to 5 per season Herbicide: Burndown/Roundup before planting.

5 Data Collected Grain yield Planting and harvest Soil skin N Number of irrigations Fertilizer amounts

6 Grain Yield: No-till vs. Conservation-till Corn Yield: CT vs. NT Grain yield, Kg/ha Years CT NT

7 Rainfall ( ) 40 Stoneville, MS Rainfall, cm Average: Months

8 Observations Corn Yield: CT vs. NT All the good rainfall years, CT fared better than NT, In Irrigated drought years, NT fared better than CT Irrigations were arbitrary: No irrigation scheduling Grain yield, Kg/ha Stoneville, MS Years CT NT Rainfall, cm Average: Months

9 Investigate if altered management can overcome observed deficiencies in the No-till system? Approach: Our goal Quantify tillage affects on C, N, H2O, and energy dynamics in corn cropping systems.

10 Irrigation scheduling Accurate ET data is the primary input. No direct measurements possible Closest to direct measurement is Weighing lysimeters - half century of crop ET investigations to advance efficient irrigation, but Important to develop timely solutions

11 ET Measurement and challenges - Lysimeter Not suited for flood/furrow irrigated systems

12 Modern Methods Eddy Covariance (EC) Residual Energy Balance (REB)

Residual Energy Balance approach for ET Estimate ET from energy balance measurements Rn = LE + Go + H + S air + S bm + S ph Rn net energy absorbed Go - can be measured

13 Residual Energy Balance approach for ET Estimate ET from energy balance measurements Rn = LE + Go + H + S air + S bm + S ph Rn net energy absorbed Go - can be measured at a depth (8-10 cm) and estimated at 0 cm. H = can be estimated S air can be estimated S bm - can be estimated S ph - can be estimated LE = estimated as a residual energy

Measurements Net radiation Air Temperature (T), Relative Humidity(RH), Wind speed (WS), Density of air, and Atmospheric Pressure Soil Heat Flux, Water, and

14 Measurements Net radiation Air Temperature (T), Relative Humidity(RH), Wind speed (WS), Density of air, and Atmospheric Pressure Soil Heat Flux, Water, and Temperature Radiative canopy temperature Vertical profile of T, RH, and WS for deriving aerodynamic temperature Crop height, and LAI Crop growth and development data

15 Soil Heat Flux - Go T t G0 G8 scs z C s = % Minerals * C m + % OM * C om + % SWC * Caw C m = 1.9 MJ m -3 O C -1 C om = 2.5 MJ m -3 O C -1 C sw = 4.2 MJ m -3 O C -1 (DeVries, 1963)

16 Sensible heat flux - H H = ρ a C p (T o -Ta)/r a Where, ρ a - density of air (kg/m -3 ), C p - specific heat at constant pressure, T o - surface aerodynamic temperature i.e. T at height Z H + d r a - aerodynamic resistance (s m -1 ) to sensible heat transfer. C p of dry air - ~1005 J kg -1 O K -1

17 Calculation of density of moist air: a Pd Pw RdT RwT T = air temperature, O K; P d = partial pressure of dry air; and P w = partial pressure of water vapor. R d = gas constant for dry air = J kg -1 O K -1 R w = gas constant for water vapor = J kg -1 O K -1 P d = P- P w (P- measured at co-agmet station). P w = P sat * RH Psat *10 7.5T T 35.85

18 H = ρ a C p (T o -Ta)/r a Surface aerodynamic temperature (T o ) for corn Chaves et al. (2005) developed models for estimating T o T a, T s_rs, u, and LAI _RS : using T o = [(0.534 T s )+(0.39 T a )+ (0.224 LAI)- (0.192 u) ]. We can also calculate it from the logarithmic temperature profile equation for surface layer: T u * H z d 0.4 C u* zh ( z) T0 ln p T(z) is the mean air temp. at height, z; zh is roughness parameter for sensible heat transfer; 0.4 is von Karman s constant; u* is friction velocity, d is zero plane displacement.

19 Estimation of r a Factors effecting r a Wind speed < 0.1 m/sec (calm ) OR > 0.1m/sec Stability of the air layer i.e. T o < T a Stable T o > T a Unstable T o = T a Neutral

20 When, u > 0.1 m s z d z ra ln u k z 0 u = 2 m wind speed (m s -1 ) k = 0.41 (von Karman s const. ) z = wind height (m) -1 d = zero plane displacement (m) z o = roughness length for sensible heat (m) φ = the stability correction Logarithmic wind Profile equation (z m = roughness length for momentum transfer (m). u ( z) u* z d ln 0.4 zm z o and d can be estimated from plant height (h c ) (Jacobs and Van Boxel., 1988) for corn: d = 0.75 h c z o = 0.25 (h c -d)

21 z d z ra ln u k z 0 The stability correction term, φ, For stable conditions (T o < T a ): (Mahrt and Ek., 1984) φ = ( Ri) (1 + 5 Ri) 1/2 where R i is the Richardson number, and Ri gt ( ats)( zd) ( Ta ) u 2

22 z d z ra ln u k z 0 For unstable conditions (Ts > Ta): Where, 115 Ri 1 K( R) i K 75k 2 1/2 1 [( zd zo)/ zo] 1/2 2 {ln[( z d zo) / zo]} k is von Karman s constant

23 z d z ra ln u k z 0 For neutral stability (Ts Ta) < 1 o C) And when u < 0.1 m s 1 r a = 1720 ms -1 When, (Ts - Ta) > 0.1 O C and u < 0.1 m s 1 r a a c 1.52 Ts Ta p 1/3

24 Rn = LE + Go + H + S air + S bm + S ph Air storage: S air S C z C z T air a pdry t w pwet T t

25 Biomass storage, S BM (Wilson and Baldocchi, 2000) T B M S B M ( C B M ib M i ) t Rn = LE + Go + H + S air + S BM + S ph i - different elements of aboveground BM, T - change in temperature of biomass type, i during t, Ci = specific heat of the relevant biomass type

26 Energy Balance in the CT vs. NT

27 Energy Balance in the CT vs. NT

28 Energy Balance in the CT vs. NT

29 Energy Balance in the CT vs. NT

30 Comparison between Lysimeter and REB First year: Corn planted and collecting data Lysimeter ET in Cotton (Bushland, TX data) Lysimeter, mm EnergyBalance Sasi ET, mm DOY

31 Questions?

Evapotranspiration. Here, liquid water on surfaces or in the very thin surface layer of the soil that evaporates directly to the atmosphere

Evapotranspiration. Here, liquid water on surfaces or in the very thin surface layer of the soil that evaporates directly to the atmosphere Evapotranspiration Evaporation (E): In general, the change of state from liquid to gas Here, liquid water on surfaces or in the very thin surface layer of the soil that evaporates directly to the atmosphere