Imazethapyr, alone and in combination with other herbicides, was applied PPI, PRE, and POST to pinto beans to determine weed control and selectivity to the crop. All of the herbicides improved pinto bean yield as compared with the unweeded control. Imazethapyr applied PPI and POST provided excellent control of black nightshade, kochia, Russian thistle, prostrate pigweed, and redroot pigweed. Barnyardgrass control with imazethapyr ranged from 58 to 96% and increased to 98% or greater when imazethapyr was combined with metolachlor, pendimethalin, trifluralin, or EPTC. Pinto bean yield was not reduced from any herbicide treatment compared to the handweeded control.

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Under the semiarid climate of the Southwest United States, accurate estimation of crop water use is important for water management and planning under conservation agriculture. The objectives of this study were to estimate maize water use and water productivity in the Four Corners region of New Mexico. Maize was grown under full irrigation during the 2011, 2012, 2013, 2014 and 2017 seasons at the Agricultural Science Center at Farmington (NM). Seasonal amounts of applied irrigation varied from 576.6 to 1051.6 mm and averaged 837.7 mm and the total water supply varied from 693.4 to 1140.5 mm. Maize actual evapotranspiration was estimated using locally developed crop coefficient curve and the tabulated United Nations Food and Agriculture Organization (FAO) crop coefficients, and from this maize water productivity was determined. Maize actual daily evapotranspiration (ETa) varied from 0.23 to 10.2 mm and the seasonal ETa varied with year and ranged from 634.2 to 697.7 mm averaging 665.3 mm by the local Kc curve, from 687.3 to 739.3 mm averaging 717.8 mm by the non-adjusted FAO Kc values, and from 715.8 to 779.6 mm averaging 754.9 mm with the FAO adjusted Kc values. Maize irrigation requirements varied from 758.4 to 848.3 mm and averaged 800.2 mm using the local developed Kc and varied from 835.5 to 935.6 mm and averaged 912.2 mm using FAO Kc. The net irrigation requirement varied from 606.8 to 678.6 using local Kc curve, and from 682.78 to 748.5 mm when adopting the FAO Kc values. Average irrigation requirement was 641 mm under the local Kc option and 730 mm under FAO Kc values option. Maize crop water use efficiency (CWUE) ranged from 1.3 to 1.9 kg/m 3 and averaged 1.53 kg/m 3 , evapotranspiration water use efficiency (ETWUE) values were higher than CWUE and varied from 2.0 to 2.3 kg/m 3 , averaging 2.1 kg/m 3. Maize irrigation water use efficiency (IWUE) was varied with years and averaged 1.74 kg/m 3. There were strong relationships between maize CWUE and maize seasonal irrigation amounts of IWUE and the seasonal irrigation amounts with R 2 of 0.97 and 0.92, respectively. Maize CWUE increased linearly with maize IWUE with a coefficient of determination R 2 of 0.99, while IWUE showed a strong quadratic relationship with ETWUE (R 2 = 0.94). The results of this study can be used as a guideline for maize water management under the semiarid conditions in northwestern New Mexico and other locations with similar climate and management conditions. Irrigation requirements for maize should be adjusted to the local meteorological conditions for optimizing maize irrigation requirement and improving maize water productivity.

Gypsum has a long history as a soil amendment. Information on how flue gas desulfurization (FGD) gypsum affects soil, water, and plant properties across a range of climates and soils is lacking. We conducted a meta‐analysis using data from 10 field sites in the United States (Alabama, Arkansas, Indiana, New Mexico, North Dakota, Ohio, and Wisconsin). Each site used three rates each of mined and FGD gypsums plus an untreated control treatment. Gypsum rates included a presumed optimal agronomic rate plus one rate lower and one rate higher than the optimal. Gypsum was applied once at the beginning of each study, and then data were collected for 2 to 3 yr. The meta‐analyses used response ratios (R) calculated by dividing the treatment value by the control value for crop yield or for each measured element in plant, soil, and vadose water. These R values were tested for their significance with z values. Most R values varied only slightly from 1.00. Gypsum significantly changed more R values from 1.00 for vadose water than for soil or crop tissue in terms of numbers of elements affected (11 for water, 7 for soil, and 8 for crop tissue). The highest R value for soil was 1.57 (Ca) which was similar for both mined and FGD gypsum, for crop tissue was 1.46 (Sr) for mined gypsum, and for vadose water was 4.22 (S) for FGD gypsum. The large increase in Ca and S is often a desired response to gypsum application. Lowest R values occurred in crop tissue for Mg (0.89) with FGD gypsum and for Ni (0.92 or 0.93) with both gypsums. Although some sites showed crop yield responses to gypsum, the overall mean R values for mined gypsum (0.987) and for FGD gypsum (1.00) were not significantly different from 1.00 in this short‐term study. Core Ideas Meta‐analysis was used to evaluate gypsum treatments at 10 sites within the United States. Response ratios were calculated for crop yields and chemistries of soil, plants, and water. Crop yields showed both positive and negative results to gypsum treatments. Most R values for elements varied only slightly from 1.0, meaning no treatment effect. Concentrations of elements in samples were below levels of environmental concern.

The utility of water production models as irrigation management tools is dependent upon their accuracy. Development of precise water production models requires a thorough understanding of how water and other factors interact to affect plant growth and yield. The objective of this experiment was to identify significant environmental variables which control water production function (transpiration vs. yield) variability between harvests and seasons for alfalfa (Medicago sativa L.) over a seven year (1981)(1982)(1983)(1984)(1985)(1986)(1987) period in northwestern New Mexico. A single line-source design was used to supply a continuous gradient of irrigation (I) to the crop, and transpiration (T) was calculated as the difference between evapotranspiration, as estimated by the water balance method, and modeled soil water evaporation at each I level. Yield per cutting was found to be a function of T, growing degree-day accumulation, average daily solar radiation, year and harvest number within year. A multiple regression equation formulated with these variables explained 82% of the yield variability. Average yield per cut in 1981 at 50 mm ofT was 1 Mg ha -1 and in 1985 at the same level of T was 2 Mg ha-1 based on the regression model. Yield per cut at any given level of T, as estimated by the coefficients of this equation reached a maximum at year 5.7 and a minimum in year 1. Within a season, yield per unit T was generally greatest at cut 1 and lowest at cut 2. Total seasonal yield was found to be a function of T and year which explained 90% of yield variability. Yield varied from 0.83 Mg ha-1 to 18.1 Mg ha-1 and T varied from 186 mm to 1298 mm.A positive linear relationship between alfalfa (Medicago sativa L.) yield (Y) and water, as evapotranspiration (ET) or transpiration (T), has been recognized by various researchers (Bauder et al. 1978;Retta and Hanks 1980;Sammis 1981;Wright 1988). As pointed out by Vaux and Pruitt (1983) however, parameters of the water producOffprint requests to." D. Smeal tion function (relationship between Y and ET, or T) are generally site and crop (or cultivar) specific. Hanks and Retta (1980) also recognized variability in the water production function between years. The prospects then are poor for developing a predictively useful, single variable, mathematical relationship between yield and water-use that is applicable among multiple harvests and years (Highstreet et al. 1987;Undersander 1987;Wright 1988). For water-production models to be accurate irrigation management tools, they must consist of complex multivariate functions that consider environmental characteristics and crop physiological development. These models could then assist irrigators in their effort to maximize water-use efficiencies and economic returns. The objective of this research was to develop a water production function for alfalfa that is applicable over a seven year period at Farmington, NM. The independent variables considered were: harvest number; year; average daily solar radiation for growing period (Sa) or...