Irrigation and Nitrogen Management for Subsurface Drip Irrigated Corn 25 years of K-State s Efforts.

Transcription

1 Irrigation and Nitrogen Management for Subsurface Drip Irrigated Corn 25 years of K-State s Efforts. Freddie Lamm Professor and Research Irrigation Engineer KSU Northwest Research-Extension Center, Colby, Kansas 1

2 Introduction??? Since its beginning in 1989, K-State SDI research has had three purposes: 1) to enhance water conservation; 2) to protect water quality; 3) to develop appropriate SDI technologies for the region. 2

3 When trying to obtain optimal crop Introduction??? production, it is easy to envision that there could be much interaction between these three goals. 1) to enhance water conservation; 2) to protect water quality; 3) to develop appropriate SDI technologies for the region. For example, an SDI design that allows plants to have equal opportunity to applied water can also result in efficient use of available soluble nutrients limiting the chances for nutrient leaching. 3

4 Conserving Water When properly managed, there is no need for any type of irrigation system to waste water!! Using a similar train of thought, no irrigation system can save water!! Only a human action or decision can actually save water!! 4 of 28

5 Conserving Water My discussion here will be limited to improvements in water usage at the farm level that can be obtained on a real-time basis. Whether the water is actually conserved or is being extended to another beneficial use will not be the topic of this discussion. 5

6 Can you save water with SDI? Subsurface drip irrigation (SDI) applies water below the soil surface to the crop root zone through small emission points (emitters) that are in a series of plastic lines typically spaced between alternate pairs of crop rows. Designed emitter discharge typically range from 0.6 to 4 L/hr. 6

7 Can you save water with SDI? SDI can be used for small, frequent just-in-time irrigation applications directly to crop root system. 7

8 The primary ways that SDI can potentially increase crop water productivity and also save water are: Reduction and/or elimination of deep drainage, irrigation runoff, and soil water evaporation Improved infiltration, storage, and use of precipitation Improved in-field uniformity and targeting of water within plant root zone Improved crop health, growth, yield, and quality So, these are the conceptual reasons! 8 So, how can you save water with SDI??

9 Evidence of the water savings Relative WP In four different K-State studies at Colby, Kansas, spanning the period 1989 through 2004, and Relative corn yield RYield = FFI FFI 2 RSQUARE = 0.49 SE= 0.15 SDI Water Requirement, SDI Fertilizer, (Standard Fertilizer Trt) SDI Irrigation Capacity, (Hi Population Trt) SDI Frequency, (Hi Population Trt) Fraction of full irrigation 0.9 both plateaued at 80% of full irrigation RWP = FFI FFI 2 RSQUARE = 0.27 SE= 0.14 SDI Water Requirement, SDI Fertilizer, (Standard Fertilizer Trt) SDI Irrigation Capacity, (Hi Population Trt) SDI Frequency, (Hi Population Trt) Fraction of full irrigation

10 Evidence of the water savings Water amount (mm) Yield (Mg/ha) An early K-State SDI study ( ) indicated we could maintain yields at 75% of full irrigation and that one of the major reasons was through reduction of early season drainage losses. That is, we were more closely matching corn water needs with smaller and more timely irrigation events SDI Corn Yields, Colby, KS Yield resulting from irrigation Yields resulting from AET Yield = AET AET and Irrigation (mm) SDI Water Requirement Study, Seasonal ETc for corn Seasonal deep percolation Seasonal irrigation amount No Irrigation treatment (Percentage of ETc replaced) 10

11 Evidence of the water savings A later study at Colby, , indicated even small amounts of daily SDI can have good results in corn production. Relative corn yield In 1998, with normal, but nearly perfectly timed precipitation, a maximum corn yield of 19.1 Mg/ha occurred with an irrigation capacity of 6.35 mm/day (Total irrigation 286 mm) Irrigation capacity (mm/d) of 28 Large yield increase Season precipitation, 322 mm Maximum corn yield, 19.1 Mg/ha 85,393 p/ha 77,409 p/ha 70,680 p/ha 61,352 p/ha

12 Evidence of the water savings Small amounts of daily SDI provided even more dramatic results in an extreme drought year. Relative corn yield Large yield increase Season precipitation, 158 mm Maximum corn yield, 16.1 Mg/ha 80,011 p/ha 70,861 p/ha 63,146 p/ha 55,971 p/ha Irrigation capacity (mm/d) In 2000, with 50% of normal precipitation, a maximum corn yield of 16.1 Mg/ha occurred with an irrigation capacity of 6.35 mm/day (Total irrigation 457 mm). 12

13 Evidence of the water savings Good yields were obtained with small irrigation capacities in both the normal and drought years. Irr Cap (mm/d) Irrigation (mm) Yield (Mg/ha ) No Irr Yields for greatest plant density are shown in Table. Relative corn yield Relative corn yield Season precipitation, 322 mm Maximum corn yield, 19.1 Mg/ha 85,393 p/ha 77,409 p/ha 70,680 p/ha 61,352 p/ha Irrigation capacity (mm/d) 2000 Season precipitation, 158 mm Maximum corn yield, 16.1 Mg/ha 80,011 p/ha 70,861 p/ha 63,146 p/ha 55,971 p/ha Irrigation capacity (mm/d) 13

14 ASW (mm/2.4 m) Evidence of the water savings Our thoughts on these deep silt loam soils in western Kansas are that irrigation capacities of as low as 4.3 mm/day provide a large enough portion of corn water needs that mm/d 5.1 mm/d 4.3 mm/d 3.3 mm/d 2.5 mm/d No irrigation SDI Irrigation Capacity, 2000 Hi Plant Population Day of year the corn can scavenge the soil profile for the daily remainder without excessive water stress. 14

15 Corn yield (Mg/ha) There is growing evidence from our K-State studies and others in the Great Plains that SDI can stabilize yields at a greater level than alternative irrigation systems when deficit irrigated Does SDI really increase crop per drop? KSU-NWREC Colby, Kansas Incanopy sprinkler, (Wet years) Incanopy sprinkler, (Dry years) Subsurface drip, (Wet years) Subsurface drip, (Dry years) Irrigation capacity (mm/day) Caveat: Although we believe this is true for most crop years, we have found that SDI sometimes experiences some reduction in kernel set in extremely dry years. We continue to research this problem. 15

16 Protecting water With SDI we can spoon-feed both water and nutrients and as a result better manage the two. quality with SDI We can limit the amount of deep drainage and eliminate irrigation runoff and apply nitrogen just-in-time as needed. 16

17 Depth (m) Protecting water quality In an early study at Colby, , we found nitrogen applied with SDI redistributed differently in the soil profile than surfaceapplied preplant N Preplant Surface Applied N May 1990, initial conditions Oct 1990, after 245 kg/ha Oct 1991, after 490 kg/ha SDI Injected N May 1990, initial conditions Oct 1990, after 280 kg/ha Oct 1991, after 515 kg/ha Nitrate Concentration (mg/l) 17 of 22 Because residual soil-n levels were greater with SDI fertigation, this lead us to study if SDI fertigation N needs could be lowered.

18 Corn grain yield (Mg/ha) WP (Mg grain /ha-cm) ANU (Mg N/ha) Show me evidence of protecting water quality while retaining excellent corn yields! As a result, we SDI Fertigation, Colby, KS, developed a BMP in 1994 irrigation, 277 mm irrigation, 305 mm the mid-90s that 1996 irrigation, 152 mm stated a nitrogen fertigation level of kg N/ha with the total applied Yield nitrogen including Apparent Nitrogen Uptake 2 Water Productivity 0.04 other non-fertigation applications to be Applied nitrogen (kg/ha) 210 kg N/ha. Irrigation is to be scheduled and limited to replace 75% of ET. Unity line for Applied vs. Uptake Note: Yield, nitrogen uptake and water productivity all plateau at 210 kg N/ha. 18

19 Depth (cm) Protecting water quality while retaining excellent corn yields! After 4 years of continuous application of the fertigation trts., nitrate-n levels in the soil were increasing and moving downward when the fertigation rate exceeded 180 kg N/ha. (Equivalent to 210 kg N/ha total) SDI Fertigation, Colby, KS Nitrogen profiles at study end, 10/14/96 Injected N-rate None 90 kg/ha 135 kg/ha 180 kg/ha 225 kg/ha 270 kg/ha Nitrate Concentration (mg/kg) This emphasizes that high-yielding corn production can be environmentally sound, efficient in both nutrient and water use. 19

20 Achieving the goals of conjunctive management of water and nutrients with SDI CAVEAT: When water and nutrients are highly managed for greatest effectiveness, there can be less margin of error. Be diligent in observing the crop performance and monitoring the SDI system. As we move forward, we may use sophisticated methods, but there are some easy methods too. 20

21 For example, if you observe this SDI corn field experiencing nitrogen stress due to dry surface soil conditions despite having abundant nitrogen reserves in the soil surface layers. The preplant surface-applied N was positionally unavailable to the crop during drought. One should immediately apply N through the SDI system to remedy this nitrogen deficiency. 21

22 Water application with deeper SDI systems is largely unobserved. Waiting until the corn wilts is not the cue! Or you fail to observe this MONITOR your flowrates and pressures! 22

23 It cannot be overemphasized that management and technology go hand-in-hand and both can only be optimized in the presence of the other. 23

24 Comments or Questions?? Google SDI in the Great Plains 24