Institute of Ag Professionals

Transcription

1 Institute of Ag Professionals Proceedings of the 2013 Crop Pest Management Shortcourse & Minnesota Crop Production Retailers Association Trade Show Do not reproduce or redistribute without the written consent of author(s).

2 Advancing Agronomic Management to Mitigate Drought Stress in Corn Jeff Coulter Extension Corn Specialist z.umn.edu/corn

3 From Rhoads & Bennet (1990); Shaw (1988)

4 Corn response to irrigation timing (sandy soil in Illinois during 1988 drought) Irrigation timing Yield (% of maximum) Full irrigated 100% Not irrigated 17% Planting to silking 27% Silking to maturity 88% From Hoeft et al. (2000)

5 ET = Evaporation (E) + transpiration (T) Water use in corn: E = 25% T = 75% Transpiration cools leaves (carries away heat) Transpiration drives nutrient transport Transpiration is an unavoidable consequence of the need for the interior of the leaf to be open to the outside air so it can take in CO 2

6 Gradients of water potential cause movement of water from soil to plant to atmosphere -3 bars = soil near root -5 bars = soil adjacent to root -6 bars = xylem in root (tissue for transporting water) -8 bars = xylem in leaf -70 bars = air inside stomata -700 bars = air just outside stomata -950 bars = air beyond unstirred layer adjacent to leaf

7 Typical scenario in the Corn Belt Water surplus in spring Water deficit during grain filling

8 Available soil water Lamberton, MN 2013 vs. historic average ( ) Plant available soil water (inches) SoilMoisture/2013vsHistoricAverage/index.htm

9 Drought stress during vegetative stages Reduces plant height Can reduce ear length

10 Drought stress around pollination Delays silking: Severe drought stress can delay silk emergence until pollen shed nearly complete Causes kernel abortion, especially for the latefertilized kernels near tip of the ear

11 Drought stress during grain fill Promotes early senescense = less leaf area for photosynthesis Shortens grain filling period = lighter kernels Predisposes plants to stalk rots & stalk lodging

12 Reduce the risk of drought stress 1. Promote water infiltration = protect soil organic matter & avoid destroying soil structure 2. Promote soil permeability (water movement under saturated conditions) = avoid compaction & protect soil aggregates 3. Reduce potential for soil crusting = limit tillage & leave surface residue after planting 4. Plant early = build root system before the soil dries out; complete pollination & kernel set before driest part of season

13 In the absence of subsoil moisture, excess leaf area & water use during vegetative growth can deplete soil water before the sensitive reproductive stages

14 Reduce the risk of drought stress 5. Promote root growth = timely planting facilitates moist soil for deep roots. If not impaired, roots can grow 1-3 ft. deep under irrigation & 5-7 ft. deep without irrigation 6. Plant hybrids of varying maturity = spread risk of moisture stress at pollination 7. Hybrid drought tolerance & root ratings 8. Manage plant population 9. Optimum fertilization = promote crop growth & efficient water utilization 10. Control weeds = weeds use large amounts of water

15 Yield potential & stress tolerance are related For environments with severe drought stress, breeding has focused on reducing the risk of total yield loss: Decreased water use = lower yield potential when no to moderate drought stress Less leaf area Lower rates of transpiration Earlier silking & maturity From Lopes et al. (2011)

16 Yield potential & stress tolerance are related For environments with no to moderate drought stress, breeding has focused on: Increasing yield potential through shoot mechanisms Increased transpiration rates Increased stay green Maintaining growth under declining water status From Lopes et al. (2011)

17 New drought-tolerant hybrids How do new drought-tolerant hybrids compare with normal high-yield hybrids in MN: In the absence of drought stress? Under varying degrees of controlled drought stress? Is this affected by N supply? No side-by-side evaluation of new drought-tolerant hybrids & agronomics under controlled drought stress in MN

18 Drought stress study in timings of drought stress: None Stress from R2 R6 Stress from V14 R6 2 hybrids: drought-tolerant vs. not 3 N fertilizer rates: 0.5X; 1.0X; 1.5X 3 levels of soil N supply potential due to previous crop: Low (rye); moderate (soybean); high (alfalfa)

19

20 Rainfall & irrigation amounts

21

22 No stress Drought stress

23 Hybrids tested Normal hybrid: NK Brand N36A-3000GT 96-day relative maturity Selected for maximum yield when no drought stress Drought-tolerant hybrid: NK Brand N42Z-3011A 99-day relative maturity Agrisure Artesian TM Technology

24 N application by previous crop 40 lb N/ac at planting; remainder sidedressed at V6

25 1) Anthesis began 3 days later for the drought-tolerant hybrid 2) Anthesis-silking interval was slightly narrower for the drought-tolerant hybrid (averaged across previous crops, drought stresses, & N rates) LSD (0.10)

26 1) Anthesis occured earlier when no drought stress 2) Inconsistent effect of N rate on the start of anthesis (averaged across previous crops & hybrids) LSD (0.10) Time of drought stress

27 1) Anthesis silking was 1 to 1.5 days earlier when no stress 2) Little effect of N rate on anthesis silking interval (averaged across previous crops & hybrids) LSD (0.10) Time of drought stress

28 Chlorophyll meter used to assess: - leaf chlorophyll (indicator of leaf N concentration) - stay green

29 Drought stress reduced chlorophyll & accelerated its decline (averaged across previous crops, hybrids, & N rates) LSD (0.10)

30 Drought-tolerant hybrid had lower chlorophyll levels (averaged across previous crops, drought stresses, & N rates) LSD (0.10)

31 N deficiency reduced chlorophyll & accelerated its decline (averaged across previous crops, drought stresses, & hybrids) LSD (0.10)

32 No drought or N stress Drought stress V14 R6 & N stress (0.5X N rate)

33 Silage yield was higher with drought-tolerant hybrid (+3% for R2 R6; +9% for V14 R6) (averaged across previous crops & N rates) LSD (0.10)

34 1) Yield was 11% higher with drought-tolerant for V14 R6 2) Yield was similar for R2 R6 & V14 R6 with drought-tolerant (averaged across previous crops & N rates) LSD (0.10) Time of drought stress

35 Normal hybrid, no drought stress Normal hybrid, stress V14 R6 Drought-tolerant, no drought stress Drought-tolerant, stress V14 R6

36 Silage yield with 0.5X N rate was 8-10% less when drought stress, but 22% less when no drought stress (averaged across previous crops & hybrids) LSD (0.10)

37 Grain yield with 0.5X N rate was 12-16% less when drought stress, but 27% less when no drought stress (averaged across previous crops & hybrids) LSD (0.10) Time of drought stress

38 0.5X N rate, no drought stress 0.5X N rate, stress V14 R6 1.0X N rate, no drought stress 1.0X N rate, stress V14 R6

39 1) Silage yield did not differ among N rates after alfalfa 2) Silage yield was less with the 0.5X N rate after soybean & rye (averaged across drought stresses & hybrids) LSD (0.10)

40 1) Top yield with 1.5X N rate, & with 1.0X N rate after alfalfa 2) Yield loss with 0.5X N rate was largest after soybean & least after alfalfa (averaged across drought stresses & hybrids) LSD (0.10)

41 Alfalfa, 0.5X N rate Alfalfa, 1.0X N rate Soybean, 0.5X N rate Soybean, 1.0X N rate

42 Summary Drought affects corn in MN each year & it is most common during the 2 nd half of the growing season Drought-tolerant hybrids have not been evaluated under controlled drought stress in MN, leading to variable results that are linked to site-specific weather We compared a popular drought-tolerant hybrid for central MN to a representative high-yield check hybrid

43 Summary Grain & silage yields did not differ among hybrids when no drought stress Drought-tolerant hybrid had higher silage yield when stress (+3% for R2 R6; +9% for V14 R6) Drought-tolerant hybrid had 11% higher grain yield when drought stress from V14 R6 Grain yield of drought-tolerant hybrid was similar when drought occurred from V14 R6 or R2 R6

44 Summary Hybrid selection should still be based on yield & agronomic characteristics across multiple locations Drought-tolerance should not reduce yield, & can result in higher yields when drought stress, especially when it occurs around pollination Drought-tolerant hybrids do not appear to have different N requirements

45 Thank you! z.umn.edu/corn