Guide for Pressure-Sensitive Paint Testing at NASA Ames Research Center Unitary Plan Wind Tunnel

Optical measurement techniques have become a standard option for wind tunnel tests. Pressure-sensitive paint (PSP) is a mature test technique and a common experimental technique in many wind tunnels to measure the global mean static pressure on a model. PSP is a valuable tool when a more detailed distribution of the pressure is needed rather than the conventional pressure taps alone. Planning for a test with optical-based techniques can present new challenges even for experienced customer. The purpose of this paper is to provide a resource to the wind tunnel testing community and customers interested in obtaining PSP measurements on a wind tunnel model at the NASA Ames Research Centers Unitary Plan Wind Tunnel. An overview of PSP mechanics, a list of requirements for ones considering PSP measurements, and PSP deliverable details are specified

Corn Yield Response to Water Availability

Drought-tolerant technologies have become popular in hybrids for low-yielding corn environments across central and western Kansas and are marketed for their ability to produce higher grain yields with less water. The objective of this study was to compare water use, yield, and water use efficiency (WUE) of two types of drought-tolerant (DT) corn hybrids and a high-yielding non-DT hybrid. Water use and yield of two DT and one non-DT, high-yielding hybrid were compared in both dryland and irrigated situations. The average yield for the irrigated corn was 217 bu/a, and the average was 127 bu/a in dryland, representing a yield increase of 90 bu/a. The irrigated corn received a total of 10 in. more water than the dryland corn over the course of the growing season, resulting in 9 bu for each additional inch of water use averaged across the three hybrids. The irrigated corn used a mean of 20.85 in. of water, and the dryland corn used a mean of 11.66 in. of water. The WUE was 10.71 bu/in. and 10.43 bu/in. for dryland and irrigated corn, respectively. Although hybrid yields differed in the irrigated environment, water use and WUE were similar for all hybrids in both dryland and irrigated environments. One DT hybrid exhibited more stable yields across dryland and irrigated environments compared with the other DT hybrid and the non-DT hybrid

Grain Sorghum Yield Response to Water Availability

Yield effects of irrigation on sorghum and corn were compared, focusing only on the grain sorghum phase. Average water use for irrigation was 22 in., and dryland sorghum used 17 in. Average yields based on 12.5% grain moisture for dryland and irrigated sorghum were similar, with 138 bu/a for the irrigated and 142 bu/a for the dryland environment. Irrigated sorghum yields were similar, but in dryland, the Pioneer 84G62 hybrid yielded 149 bu/a, a 10 bu/a increase over Pioneer 84Y50 and DKS 53-67 hybrids, which yielded 139 bu/a and 138 bu/a, respectively. Although there was a difference in the yield between the hybrids on the dryland block, there were no significant differences between water use and water use efficiency (WUE)

Subsurface Drip Nitrogen Fertigation of Corn

The efficient management of nitrogen (N) fertilizer and irrigation is of utmost importance because they are two of the greatest expenses for corn production. This project was conducted to determine if yield and efficiency of fertilizer N in corn could be improved by applying N at later developmental stages through a subsurface drip irrigation (SDI) system. Experiments in 2014 and 2015 compared a Preplant Surface application that injected fertilizer in bands below the residue at planting, to four versions of SDI fertigation that differed in timing and total amount of N applied. The SDI Sidedress treatment concluded at corn tassel stage (VT). The SDI Maximum treatment supplied an additional 40 lb N/a through corn blister stage (R2). The SDI Sensor treatment received N fertigations after corn V10 stage only if the ratio of the SPAD readings from SDI Sensor plots to Reference plots was less than 95%. The Reference treatment received both the surface band injections and all SDI fertigations for total seasonal N application that far exceeded crop N requirements. The Reference treatment produced up to 32 bu/a more grain than the Preplant Surface treatment, but produced an average of 0.7 bushels of grain per pound of N fertilizer. The SDI Maximum treatment averaged only slightly less grain yield than the reference treatment but produced 1.15 bushels of grain per pound of N fertilizer on average. The SDI Sidedress and SDI Sensor treatments resulted in similar yields that averaged 16 bu/a more than the Preplant Surface treatment. The SDI Sidedress treatment used fertilizer N the most efficiently, producing 1.3 bushels of grain per pound of N fertilizer. Applying N into the reproductive stages of corn increased yield, but N fertilizer was used most efficiently when N applications were completed by VT. Although using the sensor to determine later N applications reduced fertilizer input slightly compared to a maximum fertilizer approach, yields were reduced enough to result in similar efficiency of fertilizer use

Cover Crop Impacts on Soil Water Status

Water is a primary concern for producers in the Great Plains; as such, research is warranted to quantify how much cover crops affect the amount of soil water available to subsequent cash crops. Cover crop mixes have been marketed as a means to conserve water in no-till cropping systems following winter wheat (Triticum aestivum L.) harvest. The objectives of this study are to quantify changes in soil profile water content in the presence of different cover crops and mixtures of increasing species complexity, to quantify their biomass productivity and quality, and to quantify the impact of cover crops on subsequent corn (Zea mays L.) yields. We hypothesized the change in soil water brought on by the cover crop treatments would be correlated to the quantity of biomass produced and the species composition, rather than mixture complexity. Soil moisture was measured using a neutron probe to a depth of 9 ft. Results from 2013–14 showed no difference in water use between cover crop mixtures and single species. Cover crops depleted the soil profile by a maximum of 3.5 in. during growth, but fallow was able to gain 0.75 in. of water during the same period. At the time of corn planting, soil moisture under all cover crops had replenished to levels at cover crop emergence, except for the brassicas, which had extracted water from deeper in the profile. Corn yields were reduced following the grass cover crops and the six-species mix. Corn yields were more closely related to the carbon:nitrogen (C:N) ratio of the cover crop residue than to profile soil moisture at corn emergence. The fact that yields were similar for corn after fallow and for corn after brassica cover crops implied that water was not the cause of yield reductions after the other cover crops

Effect of Defoliation at Different Stages on Grain Sorghum

Loss of leaf area usually results in yield loss in grain crops, but the amount of yield loss varies with extent and timing of defoliation. Grass crops, such as corn and grain sorghum, are particularly sensitive to leaf area loss near the time of seed set because there is little opportunity for the plant to compensate. An experiment to quantify yield reductions associated with various levels of defoliation imposed at different stages of grain sorghum development was conducted at Manhattan, KS, in 2022. Target defoli­ations of 0, 33, 66, and 100% were imposed at 5-leaf, flag-leaf-appearance, half-bloom, and hard-dough stages. Defoliation of 5-leaf sorghum resulted in minimal yield loss unless the defoliation rate was 100%, which delayed heading and reduced head size and seed size. Leaf area losses of 50% or more at the hard dough stage caused yield reduc­tions of only about 10–12%. Yield reductions were greatest when leaf area was lost at flag leaf appearance or half bloom. Leaf area loss of 60% and 100% caused yield losses of 25% and 75%, respectively. These yield losses were associated with different combina­tions of reductions in head size and seed size

Effect of Late Planting Dates on Corn Yield

Planting date studies have been conducted for corn over many years. Often the focus has been to determine the optimum planting date for maximizing yield. In some areas, planting early-maturing corn hybrids as early as possible has been a successful strategy for avoiding hot, dry conditions at the critical pollination and early grain fill stages. Planting later can be an alternative strategy that attempts to avoid the most intense heat by moving the critical growth stages for corn centered around pollination to later in the growing season. This strategy has been adopted by some growers in areas that often encounter heat and moisture stress during the growing season. However, crop insur­ance cutoff dates for planting are earlier than some farmers may want to plant their corn acres. The purpose of these studies was to assess the yield potential for corn planted after the insurance planting cutoff date and to compare corn yields from a wide range of planting dates

Response of Drought-Tolerant Hybrids to Environmental Yield Potential

Due to increasing non-irrigated corn acres, decreasing availability of irrigation water in some areas of western Kansas, and increasing water restrictions, producers are looking for more efficient ways to use available water. Drought-tolerant (DT) hybrid technologies are marketed for their ability to produce more stable yields in stress-prone environments. The objective of this research was to understand how DT and non-DT corn hybrids respond to a wide range of environmental conditions in terms of soil water status change, canopy indicators of stress, dry matter partitioning, and grain yield. Two DT hybrids, and one non-DT hybrid were compared in 2014 and 2015 at five locations in rain-fed, limited-irrigation, or fully irrigated regimes making a total of 18 environments. Grain yield was measured at all 18 environments, and biomass production was estimated at 14 of the environments. Yields of all hybrids were comparable in most environments, but as environment yields increased beyond 200 bu/a, one of the DT hybrids lagged behind the other two hybrids. Although one of the DT hybrids had slightly greater harvest index values than the other two hybrids in environments that resulted in a greater portion of dry matter allocated to grain, the differences were not consistent enough to be conclusive

Harvest Method, Cultivar, and Time of Swathing Effects on Yield and Oil Content of Winter Canola

Producers want to achieve the highest yield and oil content possible using either swathing or direct cutting to harvest winter canola. Multi-year experiments were conducted to evaluate the effects of harvest method (swathing versus direct cutting) and cultivar on seed moisture, yield, and oil content; and to evaluate the effects of swathing timing on yield and oil content. The harvest method experiments were conducted for two seasons at the Redd Foundation Field near Partridge, KS. The time of swathing experiments were conducted for two seasons near Manhattan, KS. In 2016 and 2017, harvest method had a significant effect on seed moisture, yield, and oil content. Swathing produced seed with lower moisture content and greater yield, but direct cutting produced seed with the highest oil content. Cultivars differed in their response to yield depending on the harvest method used. Some cultivars responded positively to swathing, others responded positively to direct cutting, and some showed no response to harvest method. Time of swathing had a significant effect on yield and oil content. As a rule, as seed color change progressed, yield and oil content increased. All swathing treatments had greater yield than direct cutting except when swathing was done at green seed. Seed from direct cutting had significantly greater oil content than seed from all swathing treatments. Both swathing and direct cutting can be used effec­tively to harvest winter canola

Long-Term Cover Crop Management Effects on Soil Health in Semiarid Dryland Cropping Systems

Growing cover crops (CC) in semiarid drylands may provide benefits to soil health. This study examined long-term CC management effects in a no-till winter wheat-grain sorghum-fallow cropping system in southwest Kansas. Objectives were to assess the impacts of CCs on 1) soil organic carbon (SOC) and nitrogen (N) stocks, 2) soil susceptibility to erosion, as well as to 3) quantify the effects of haying cover crops as annual forages. Treatments were spring-planted and included peas for grain as well as one-, three-, and six-species CC mixtures of oats, triticale, peas, buckwheat, turnips, and radishes compared with conventional chemical-fallow. Half of each CC treatment was harvested for forage. All phases of each rotation were present every year. Soil samples were collected from the 0- to 6-inch depth in 2018 and 2019 corresponding with wheat planting and harvest in the three-year rotation. Results indicate no significant difference in SOC with CCs compared to fallow in either 2018 or 2019, though SOC stocks were greater than in 2012. This was possibly due to periods of drought reducing total carbon (C) inputs compared to earlier periods of relatively greater precipitation. Haying of CCs had no effect on soil health indicators compared to when CCs were left standing. Soil N was not increased with CCs compared to fallow or peas. Mean weight diameter of wet aggregates in 2018 was not different between CCs hayed (0.042 in.) and CCs left standing (0.044 in.) but were greater than fallow (0.033 in.) or peas (0.030 in.). Growing a CC significantly increased the proportion of larger (0.30- to 0.08-in.) aggregates (37%) compared to peas (21%) but not compared to fallow (24%). These differences were not significant after wheat harvest in 2019. Our findings suggest that CCs may improve soil physical properties compared to conventional chem-fallow in semiarid dryland cropping systems