Nutrient availability Temperature Daylength Solar radiation Soil moisture/ RainIrrigation Fertilizer Population Sowing date Cultivar Mineral nutrition Phenological development Canopy development Biomass accumulation Partitioning Yield Quality PROCESSES ENVIRONMENT MANAGEMENT Relationship between environment and management factors and the physiological processes that regulate crop yield and quality. (Source: Hay & Porter 2006).

Light  Complex & dynamic signal  Quantity of light  photons falling /area/time  Quality of light  plant responses

Growth vs Development Growth: an irreversible increase in DM - function of light interception and - photosynthesis and then - assimilate partitioning Development: irreversible change in the state of an organism - fixed pattern and reversion is rare Eg. silking, pod initiation, dough development

A) Vegetative Emergence and Leaf appearance rates (phyllochron). B) Reproductive Time of flowering (anthesis), Duration of grain fill. Driven by temperature modified by photoperiod and vernalization Plant development

Sowing to emergence Thermal time - soil temperature

Temperature (°C) Days to 75% germination Ryegrass Time for germination

Germination rate (1/days) Temperature (°C) Germination rate TbTb T opt Tt = 65 ° Cd T max

Thermal time Tt = Thermal time (°Cd) = Tmax + Tmin - T b 2 Growing degree days (GDD) Heat units (HU)

Tb=Tb= Temperature ( o C) Whero 27 o Cd/node Development rate (nodes/d) Massey 37 o Cd/node Temp.Interval

Crop Growth and Yield 1)C = E*Q C = daily rate of DM prod. E = radiation use efficiency Q = PAR intercepted 2)Y = HI*C*dtY = seed yield/unit area HI = harvest index

Year Yield Height HI BY (t/ha) (m) (%) (t/ha) Little Joss LJ (low fert.) Cap- Dep rht 2 Hobbit Norman Nor. (low fert.) Change in HI over time

Light - photosynthesis to produce CHO’s for growth. - Photosynthetically active radiation (PAR) is in the visible range ( nm). - Conversion of PAR to DM ~2.5 g DM /MJ/m 2 for C3 plants ~3.8 g DM /MJ/m 2 for C4 plants

Dryland Irrigated Total DM production (C) from successive harvests and intercepted PAR (Q) for field peas in 5 experiments in 4 seasons with different cultivars, sowing times and irrigation treatments. The form of the regression is: 2.36±0.03 g DM/MJ PAR (R 2 =0.97). Source: Wilson 1987

Intercepted solar radiation (GJ/m 2 ) Total DM (t/ha) Intercepted solar radiation (GJ/m 2 ) Total DM (t/ha) Apples Barley Potatoes Sugar beet (Source: Monteith, 1977)

Time of day (h) Irradiance (W/m 2 ) December (14.4 MJ PAR/m 2 /d) March (6.5 MJ PAR/m 2 /d) June (2.2 MJ PAR/m 2 /d) Global irradiance on sunny days (W/m 2 )

Photosynthetically active radiation (PAR) PAR averages11.4 MJ/m 2 /d in summer (Dec) 2.2 MJ/m 2 /d in winter (Jun) and therefore potential dry matter yield is: summer: 11.4 x 2.5 = 28.5 g/m 2 = 285 kg DM/ha/d winter: 2.2 x 2.5 = 5.5 g/m 2 = 55 kg DM/ha/d Conclusion: Available PAR levels are non-limiting for pasture production in New Zealand

Pasture production in Canterbury Potential Actual

Potato Proportion of incident PAR intercepted (%) Green Area Index Proportion of incident PAR intercepted (%) Critical GAI (Source: Khurana & McLaren 1982)

Leaf area index (LAI) = area of leaf lamina (m 2 ) area of soil surface (m 2 ) influenced by; i) Species LAI Cmax (kg/ha/d) white clover ryegrass mixture maize

Measurements Light environment Photosynthesis Soil moisture Chemical Analysis: -N (shoots and roots) -Starch in roots -Soluble sugars in roots Others: - SLW - SPAD - Chl a+b

Light level (PPFD  mol m 2 /s) Photosynthetic rate  mol CO 2 /m 2 /s Non Limited Nitrogen 3.5% Temperature 14 o C Predawn LWP -10 bar (Source: Peri et al. 2002)

Pmax s (dimensionless) Temperature ( o C) Pmax s = 0.99 x e(-0.5 x (T-20.4/7.90) 2 ) o C (Source: Peri et al. 2002)

Predawn leaf water potential (bars) Pmax s = x Pmax s (dimensionless) (Source: Peri et al. 2002)

Foliage N concentration (g N/kg DM) % N5.2% N Pmax s (dimensionless) (Source: Peri et al. 2002)

Modelling photosynthesis C C Pmax s %NPmax s f (T) f (N) f (  lp )  lp Pmax s * * Pp max * Where Pp max is maximum measured photosynthetic rate of 27.4  mol CO 2 m -2 s -1 Most basic approach (Source: Peri et al. 2002)

200 kg N/ha anthesis Control (0 N) Days after crop emergence Green leaf area index kg N/ha (Source: Green 1987)

Effect of water stress on relative yield Soil moisture deficit (mm) Relative yield I+N D+N y = -1.45%/mm 78 mm DLDL (Source: Mills et al. 2006)

Ryegrass Clover 50 mm 250 mm Water extraction (mm water/10 cm soil) Depth (m) Lismore Stoney loam (100 mm) Wakanui Silt loam (380 mm) Patterns of water extraction

Experiment site

Growth rates (2 year means) Month JASONDJFMAMJJ Growth rate (kg/ha/d) I +N 21.9 t/ha I -N 9.8 t/ha 15.7 t/ha D+N 6.3 t/ha D-N

Water stress effect on yield Thermal time DM yield (t/ha) I+N y = 7.0 kg DM/ha/ o Cd 21.9 t/ha D+N 15.7 t/ha 21 Nov 30 Jan (Source: Mills et al. 2006)

DM yield response to thermal time (T b = 3°C) Thermal time (°Cd) DM yield (t/ha) I+N y = 7.0 kg DM/ha/ o Cd I–NI–N y = 3.3 kg DM/ha/ o Cd 21.9 t/ha 9.8 t/ha (Source: Mills et al. 2006)

Ryegrass only 13 kg DM/ha/mm Lucerne 28 kg DM/ha/mm 20 kg DM/ha/mm Spring WUE: legume = (nitrogen) Water use (mm) Accumulated DM (t DM/ha) Ryegrass / clover (Source: Moot et al. 2008)

Clover yield (kg DM/ha) Fixed N (kg N/ha) White clover Sub clover Biological N fixation y = 28.0±0.66x (R 2 =0.96) (Source: Lucas et al. 2010)

Conclusions Light interception drives growth Nitrogen affects leaf area expansion Temperature affects leaf area expansion Water affects leaf area expansion NTW affect photosynthesis Pests and diseases affect leaf area! CANOPY MANAGEMENT