Effects of Late-Season Water Lease on Forage Crops

A. Soil Moisture Results: Dry Cottonwood Ranch (DCCR)- The original probes from the East field had to be removed due to Columbian Ground Squirrel activity and the severing of wires to the probes. These probes were put in the DCCR North field. Soil probes logged data at two locations, one irrigated and one non-irrigated (late season) in 2013 and 2014. Each location contained two probes, which were buried at depths of one and three feet. The range in soil moisture tension was not as large as the Lampert Ranch between the shallow and deep probes, although demonstrated a similar trend of declining soil moisture after irrigation was shut off in early July. In addition, the irrigated shallow probe maintained high soil moisture as a result of irrigation.

Soil testing occurred in each of the irrigated fields at DCCR and analyzed for organic matter, phosphorus, potassium, magnesium, calcium, soil PH and nitrates. Overall, soil nutrients were within normal ranges of healthy, although some inputs of additional nitrogen and phosphorus are needed in the north field. Dry Cottonwood planted a cover crop in this field in 2015 and 2016 with the intent of improving the nitrogen and phosphorus levels.

Soil moisture measurements were conducted using the feel and appearance method and recorded using the NRCS checkbook approach, which compares soil moisture to irrigation application, evapotranspiration and precipitation. Due to poor water availability and little precipitation, soil moisture in the corners of the fields was low and subsequently production was quite low (not even cut, less than .5 tons per acre). Weeds issues were present in these non-irrigated corners. Dry Cottonwood Ranch did see an increase in the Columbia Ground Squirrel, as a result from switching from flood irrigation to pivot.

Lampert Ranch- Soil probes logged data at two locations in Varney Sandy Clay Loam, one irrigated and one non-irrigated (late season). Each location contained two probes, which were buried at depths of one and three feet. The Lampert Ranch soil data from 2013-2016 demonstrated lower soil tension (wetter) in the irrigated field during the month of August. For both fields, the deep probe was highly saturated with water throughout the irrigation season, which suggests an abnormally high groundwater table. The soil moisture tension for the shallow probes was also higher (drier) than anticipated. Irrigation use stopped on 58 acres July 8th through September 25th of 2013 and 2014, 6.6 acres in 2015 and 37.4 acres in 2016. No change in water application occurred before July 8th or after September 25th.

On the Lampert ranch there was no noticeable increase in pests, although there was an increase in non-desirable grass species in some of the upper alfalfa fields participating in the split-season lease.

2 Bar Ranch- The 2 Bar Ranch was included in 2015 due to the irrigated crop types (alfalfa) and to provide diversity in both soil type and age of the alfalfa stand. The alfalfa stand was replanted relatively recently (4 years) and the partially irrigated ground was located on Carten Wetsand complex soils, while the fully irrigated comparison was located on Gregson loam soils. The two soil moisture probes were redeployed in the area irrigated after July 1 and the area that was not irrigated following first cutting on July 1.

The non-irrigated alfalfa was visibly drier, although there was no noticeable increase in weeds or impact to plant health. It is also quite possible due to the soil type and vicinity to the Racetrack Creek water source that the alfalfa benefits from a high water table and adjacent irrigation. Carten Wetsand complex soils are described as being often sub-irrigated and have poor drainage properties. The soil moisture probe data also indicates that despite a lack of irrigation beginning July 1, soil moisture did not depart from the irrigated field until late July, indicating that the roots continued to have sufficient soil moisture for nearly 4 weeks following 1st cutting.

B. Hay Yield and Clipping Results: Dry Cottonwood Ranch- 2013 Clipping data from the West field of DCCR for first crop had a total of 2550 grams between the 3 plots for an average of 850 grams. The East field of DCCR had a total of 2265 grams between the 3 plots with an average of 755 grams. A second clipping was not done on the DCCR as there was a miscommunication and 2nd cutting had already been taken off the field. Crop yields for second cutting non-irrigated alfalfa on Dry Cottonwood were approximately .25 tons per acres (producer estimate). These non-irrigated areas were not cut due to the stunted growth and excessive steminess and were instead left standing for fall cattle grazing.

2014: The West field of DCCR had a total of 2810 grams between the 3 plots for an average of 937 grams for first cutting. The East field of DCCR had a total of 2750 grams between the 3 plots with an average of 917 grams. This was an increase over 2014 partly due to more even water application by the new pivots. No clippings were conducted for second cutting since bale weights were measured and there were no acres participating in a split-season arrangement during 2014 (aside from some non-irrigated corners). Irrigated alfalfa for first cutting weighed in at 2.24 tons/acres and second cutting weighed in at 1.61 tons/acre for a total of 3.85 tons/acre.

2015: DCCR became increasing harder to monitor because of change in irrigation from flood to pivot and they are not turning any water off and some of the corners receive no irrigation at all. A comparison in the south field was performed (which had been done before). With the dry corner that is under flood and had not received any water this season at 460 grams and then the field under pivot was at 880 grams. This originally was the West field in other data that has been taken in the past. The dry corner in the North field was a very old stand of alfalfa grass and had 780 grams and no clippings were taken under the pivot as it was under a cover crop.

First cutting yields were down to 1.7 tons/acre and second cutting was 1.0 tons/acre for a total of 2.7 tons per acre. 2015 yields were lower due to drought conditions, aging alfafa and mechanical issues with the pivots. In addition to the lack of water on the non-irrigated acres, the alfalfa was also reaching the end of its productive life, which may have also contributed towards a lower yield.

2016: Clippings were not taken the DCCR ranch this year due to change in irrigation and plowing of some of the field and putting in cover crops. We did do hay sampling though for DCCR.

First cutting yields improved to 2.8 tons per acre for first cutting and 2.2 tons per acre for second cutting under the West Alfalfa pivot for a total yield of 5 tons per acre. Total yields across the three pivots were down overall due to cover crops being in place in 2 of the 3 pivots. One corner in the South field was flood irrigated for first cutting and produced 1.4 tons per acre. For second cutting, 1.06 tons per acre were harvested on the South field and the yield loss of the non-irrigated corner was approximately 0.81 tons per acre.

Yields were also lower in the irrigated fields due to cover crops, aging alfalfa stands and low soil moisture at times. With so many factors at play with DCCR in 2015 and 2016, it is difficult to draw many conclusions regarding the impacts of split-season water leasing. Cover crops such as the one planted at DCCR in 2015 and 2016 did require less irrigation application overall and may not have required late season water. For ranches looking to improve soil health, decreasing or stopping irrigation of cover crops in late July or early August could be an option for those also looking to conserve irrigation water.

Lampert Ranch- 2013 Lampert Ranch fields are alfalfa grass stands that are 4 years old. Wheel line field had a total of 2145 grams between 2 plots with an average of 1072.5 grams. Pivot Field of Lampert Ranch had a total of 2795 grams between 3 plots with an average of 932 grams.

On August 26th a second clipping was taken on the Lampert Ranch, the wheel line field had a total of 990 grams from 2 plots with an average of 495 grams. Irrigation had ceased on this field on July 5. The field had a very healthy stand with an average temperature of 81 degrees Fahrenheit and rainfall for July was 1.42 inches and August was 1.46 inches of rainfall. The pivot field had a total of 1090 grams from 2 plots with an average of 545 grams.

The yield change of .5 tons per acre for the Lampert Ranch was consistent with prior low precipitation years for this aging alfalfa stand on well drained, sandy soils. No yield change was observed on certain lower elevation acres that benefitted from an especially high groundwater table. The biggest take-away on the Lampert Ranch was the location of certain alfalfa fields and the age of the stands. Those fields located closer to the river which benefit from a higher water table were impacted much less than those fields located closer to upland grass communities.

2014 Lampert Ranch fields are alfalfa grass stands that are 5 years old, starting to see an encroachment of quackgrass, Kentucky bluegrass and dandelions especially under the pivot.

Wheel line field had a total of 1725 between 2 plots with an average of 862.5 grams. Pivot Field of Lampert Ranch had a total of 2200 grams between 3 plots with an average of 733 grams. This is down overall from 2014 mostly attributed to grass encroachment and a cool spring.

On August 20th a second clipping was taken on the Lampert Ranch, the wheel line field had a total of 2115 grams from 2 plots with an average of 1057 grams. Irrigation had ceased on this field on July 8. The field had a very healthy stand with an average temperature of 80 degrees Fahrenheit and rainfall for July was 1.67 inches and August was 1.29 inches of rainfall. The pivot field had a total of 2430 grams from 3 plots with an average of 810 grams. The yield change between the irrigated and non-irrigated fields for second crop was approximately .5 ton per acre.

2015 Only one set of clipping data was taken this year on August 18, 2015. Lampert Ranch fields are alfalfa grass stands that are 6 years old and another field the west field that as added with a stand that is at least 10 plus years old. Fields are getting more grass encroachment and dandelions. Wheel line field that had water turned off on July 8 had 970 grams total with an average of 485 grams per plot. The stand under the pivot had a total of 1275 grams with an average of 637.5 grams. Overall production is down due to Kentucky bluegrass and dandelion encroachment and aging of alfalfa plants with less production.

We put in another field at the Lamperts for the study which is the East field below the house. Irrigation ceased on half of the field on July 8 as well. Non-irrigated portion averaged 685 grams and irrigated portion had 805 grams of forage. The yield change between the irrigated and non-irrigated fields for second crop was approximately .5 ton per acre.

2016 Lampert Ranch fields are alfalfa grass stands that are 6 years old and older, the 5 acre wheel line field is about 30% alfalfa and 70 percent grass. We also included a 9 acre wheel line field that is about 60 percent grass and 40 percent alfalfa. All fields had water turned off the beginning of July. It was a dry summer and most of grass was droughted out when fields were clipped on August 27th. The field that is paired with the pivot also is seeing a lot more cheatgrass encroachment under the wheel line where water has been turned off and some pocket gopher invasion as well. Under the pivot with traditional irrigation on July 5th there was an average of 797.5 grams per plot, compared to the wheel line that had 690 grams per plot. On August 27th a second clipping was taken and the pivot had 750 grams per plot and the wheel line was at 435 grams per plot.

The 5 acre field averaged 426 grams per plot on July 5th and 257.5 grams per plot on August 27th. We added the 9 acre field as it is irrigated very similar and has an older stand of alfalfa that is comparable to the other fields at had 575 grams per plot on July 5th and 327.5 grams on August 27th. This field also has a lot of pocket gopher activity. The yield change between the irrigated and non-irrigated fields for second crop was approximately .5 ton per acre.

2 Bar Ranch- 2015 The Two Bar Ranch did not receive any clipping data since the harvested acres were weighed using the bale weight technique.

First cutting yields were 3.5 tons per acre and second cutting yields were 1.8 tons per acre for a total of 5.3 tons per acre in 2015. The 2 Bar Ranch exhibited much higher yields that other participants, which may have also resulted in a slightly higher loss per ton (.8 tons per acre) on the non-irrigated field (for second crop). The main lesson learned so far from the 2 Bar Ranch is that even on highly productive soils, the impacts of split season leasing on yield are not as significant as expected (.8 tons per acre less than irrigated 2nd crop).

The difference of .8 tons per acre in 2nd cutting yield may have also been greater if the age of the alfalfa stand in the irrigated area was replanted at the same time. The full season irrigated area alfalfa, which we used for comparison was predominately planted around 8 years ago. Overall, the non-irrigated area from July 1 onward was visibly drier at the time of cutting, despite producing only a .8 ton per acre difference (2.6 ton per acre irrigated, 1.8 ton per acre non-irrigated).

2016 DCCR Hay Production Workbook 2013-16 alfalfa clipping data DCCR Johnston Soil Data Lampert entire soil study