Jonathan Aguilar

Crop Species Diversity Changes in the United States: 1978-2012

Anecdotal accounts regarding reduced US cropping system diversity have raised concerns about negative impacts of increasingly homogeneous cropping systems. However, formal analyses to document such changes are lacking. Using US Agriculture Census data, which are collected every five years, we quantified crop species diversity from 1978 to 2012, for the contiguous US on a county level basis. We used Shannon diversity indices expressed as effective number of crop species (ENCS) to quantify crop diversity. We then evaluated changes in county-level crop diversity both nationally and for each of the eight Farm Resource Regions developed by the National Agriculture Statistics Service. During the 34 years we considered in our analyses, both national and regional ENCS changed. Nationally, crop diversity was lower in 2012 than in 1978. However, our analyses also revealed interesting trends between and within different Resource Regions. Overall, the Heartland Resource Region had the lowest crop diversity whereas the Fruitful Rim and Northern Crescent had the highest. In contrast to the other Resource Regions, the Mississippi Portal had significantly higher crop diversity in 2012 than in 1978. Also, within regions there were differences between counties in crop diversity. Spatial autocorrelation revealed clustering of low and high ENCS and this trend became stronger over time. These results show that, nationally counties have been clustering into areas of either low diversity or high diversity. Moreover, a significant trend of more counties shifting to lower rather than to higher crop diversity was detected. The clustering and shifting demonstrates a trend toward crop diversity loss and attendant homogenization of agricultural production systems, which could have far-reaching consequences for provision of ecosystem system services associated with agricultural systems as well as food system sustainability.

Irrigation Scheduling Based on Soil Moisture Sensors and Evapotranspiration

Irrigation scheduling is crucial to effectively manage water resources and optimize profitability of an irrigated operation. Tools that can be customized to a field’s characteristics can greatly facilitate irrigation scheduling decisions. Soil moisture sensors and the evapotranspiration (ET)-based KanSched are two of the tools that could be implemented in an irrigated farm. Focusing on the installation of soil moisture sensors, demonstration set-ups were established at the Southwest Research-Extension Center plots in Garden City, Kansas, and in a producer’s field, each with three types of moisture sensors at different depths. Among others, this project validates the importance of moisture sensors being installed as early as possible in a representative location with good soil-sensor contact. The moisture sensors, at the least, help in determining when irrigation water should be applied or scheduled. Furthermore, in implementing an irrigation schedule, the irrigation manager considers the irrigation system capacity, the amount that can be efficiently applied, the soil intake rate, and other relevant factors.

Mobile Drip Irrigation Evaluation in Corn

Mobile Drip Irrigation (MDI) involves attaching driplines to center pivot drops. MDI has potential to eliminate water losses due to spray droplet evaporation, water evaporation from the canopy, and wind drift. MDI also may reduce soil water evaporation due to limited surface wetting. A study was conducted with the following objectives: 1) compare soil water evaporation under MDI and in-canopy spray nozzles; 2) evaluate soil water redistribution under MDI at 60 inch dripline lateral spacing; 3) compare corn grain yield, water productivity, and irrigation water use efficiency; and 4) compare end-of-season profile soil water under MDI and in-canopy spray at two well capacities 300 and 600 gpm. The experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, Kansas. The experimental design was randomized complete block with four replications, and two treatments MDI and in-canopy spray nozzles. Soil water evaporation was measured using four-inch minilysimeters placed between corn rows. The effect of a 60-inch lateral spacing on soil water redistribution was evaluated using soil water measurements made using neutron attenuation to a depth of 8 feet. Preliminary results indicate soil water evaporation was lower under MDI compared to in-canopy spray nozzles, by 35% on average. Soil water redistribution was adequate for dripline spacing of 60 inches in silt loam soils of southwest Kansas. At 600 gpm well capacity, corn yields were 247 and 255 bu/a for MDI and in-canopy spray nozzles, respectively. At 300 gpm well capacity, yields were 243 and 220 bu/a for MDI and in-canopy spray nozzles, respectively. However, the differences were not significant (p > 0.05) between the irrigation application technologies in 2015. The effect of application method on water productivity and irrigation water use efficiency was also not significant. The lack of significant differences could be attributed to the above normal rainfall received during the 2015 growing season (18.3 inches from May to October). Normal mean annual rainfall for the study area is 18 inches. The effect of application method on end-of-season soil water was statistically significant under low well capacity (300 gpm) with Mobile Drip Irrigation having more soil water compared to in-canopy spray nozzles in the 8 foot profile at harvest. It is worth noting that plots under MDI did not have deep wheel tracks associated with sprinkler nozzles.

Forage Sorghum and Corn Silage Response to Full and Deficit Irrigation

There is limited information on forage sorghum and corn silage yield response to full and deficit irrigation in Kansas. The objective of this study was to generate information on forage sorghum (brown mid-rib hybrids (BMR and non-BMR)) and corn silage yield response to different levels of irrigation as influenced by irrigation capacity in southwest Kansas. Preliminary results indicate the effect of irrigation capacity on forage yield was significant (P = 0.0009) in 2014 but not 2015, probably due to high growing season rainfall received in 2015. Corn silage produced significantly (p < 0.05) higher biomass at all irrigation capacities compared to forage sorghum hybrids in 2015. BMR forage sorghum produced significantly lower biomass compared to non-BMR hybrid in both 2014 and 2015 (P < 0.05). The highest amounts of forage produced for corn silage, BMR, and non-BMR forage sorghum were 24.6, 17.4, and 21.1 tons/a adjusted to 65%, moisture respectively. Water productivity ranged from 1.0 to 1.4 dry matter tons/a/in. More research is needed under normal and dry years to quantify forage sorghum and corn silage yield and forage quality response to full and deficit irrigation.