Cover crops are the plants which are grown to improve soil fertility, prevent soil erosion, enrichment and protection of soil, and enhance nutrient and water availability, and quality of soil. Cover crops provide several benefits to soils used for agriculture production. Cover crops are helpful in increasing and sustaining microbial biodiversity in soils. We summarized the effect of several cover crops in soil properties such as soil moisture content, soil microbial activities, soil carbon sequestration, nitrate leaching, soil water, and soil health. Selection of cover crops usually depends on the primary benefits which are provided by cover crops. Other factors may also include weather conditions, time of sowing, either legume or non-legume and timing and method of killing of a cover crop. In recent times, cover crops are also used for mitigating climate change, suppressing weeds in crops and increasing exchangeable nutrients such as Mg 2+ and K +. Cover crops are also found to be economical in long-term experiment studies. Although some limitations always come with several benefits. Cover crops have some problems including the method of killing, host for pathogens, regeneration, and not immediate benefits of using them. Despite the few limitations, cover crops improve the overall health of the soil and provide a sustainable environment for the main crops.

Most long-term studies evaluate only average crop yields and overlook year-to-year yield variability, which could be highly significant. Our objectives were to evaluate the impact of long-term cropping systems and fertility management on corn (Zea mays L.) yield and yield stability. Cropping systems were (i) CC, continuous corn; (ii) CS, corn-soybean [Glycine max (L) Merr.]; (iii) 4C4A, 4 yr corn-4 yr alfalfa (Medicago sativa L.); and (iv) COW2RT, corn-oat (Avena sativa L.)/winter wheat (Triticum aestivum L.)-2 yr red clover (Trifolium pratense L.)/timothy (Phleum pratense L.). Fertility regimes were inorganic, or manure based on crop N or P requirements. Averaged across fertility regimes, mean corn yields in 4C4A and COW2RT were 10 to 12% higher than CC, and 7% higher in 4C4A than CS. Yield trends were similar (0.28 Mg ha -1 yr -1 ) among all cropping systems. Coeffi cient of variation (CV) analysis indicated that yield variability was highest in CC (CV = 28%) and lowest in 4C4A (CV = 21%) across fertility regimes. Regression analysis indicated that response of corn yield to the environment mean did not diff er among the cropping systems within inorganic and P-based manure fertility and corn yielded lower in CC than in 4C4A and COW2RT systems. Under N-based manure fertility, yield was lower in CC than in other systems in the poorest-yielding year, but similar in the highest-yielding year. Results suggest that, on average, rotations are likely to produce higher yields than CC across fertility regimes. In high-yielding years with N-based manure fertility, however, corn yield in monoculture may be similar to that in rotations.

Th e importance of saffl ower (Carthamus tinctorius L.) is increasing as a low input, stress-tolerant oilseed crop around the world. Adapting a crop growth model for saffl ower will help to assess the feasibility of this crop under diverse environmental conditions with relatively limited fi eld experimentation. Th e objective of the project was to adapt the Decision Support System for Agrotechnology Transfer (DSSAT) Cropping System Model (CSM-CROPGRO) to simulate growth and seed yield of spring saffl ower. Th e CROPGRO template approach was used, and parameters in species and cultivar fi les were developed based on saffl ower literature and calibration to fi eld data. Th e entered base temperatures for photosynthetic, vegetative, and reproductive processes of saffl ower ranged from 0 to 5°C while corresponding optimum temperatures varied from 19 to 40°C. Simulated results were compared with observed data collected from fi eld experiments conducted at Clovis, NM, during 2013 and 2014. Th e model predicted the crop life cycle (anthesis and harvest maturity date) with relative root mean square error (RRMSE) of 0.07. Average plant biomass, head mass, head number and seed number were satisfactorily simulated when compared to observed values. Seed yield, averaged over irrigation treatments and years, was predicted as 1963 kg ha -1 compared to measured value of 1902 kg ha -1 with RRMSE of 0.12. Reasonable prediction of phenology, growth, and yield by the model adapted for saffl ower suggested that the CROPGRO-saffl ower model is promising to simulate saffl ower production in semiarid climates. However, further testing of the CROPGROsaffl ower model under diff erent environments is needed.

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Guar (Cyamopsis tetragonoloba L.) is a drought‐tolerant summer annual legume that can be grown for forage, green pods, or seeds. Galactomannans use in various industries such as food, cosmetic, paper, and oil etc. has attracted the guar production for seed. Currently, most of the United States’ demand for guar is met through imports. Preliminary research has shown that guar can be potentially grown in semiarid irrigated conditions in southern New Mexico (NM). A 2‐yr field study was conducted from 2014–2015 to evaluate stand establishment, physiology, and yield performance of eight guar genotypes under four planting dates in southern NM. In both years, mid‐June planting resulted in better stand establishment by having higher plant density than late‐April and mid‐May plantings. The mid‐June planting resulted in higher photosynthetic rate (Pn) compared to late‐April and early July plantings. Transpiration rate (Tr), leaf area index (LAI), clusters plant−1, pods plant−1, and seeds plant−1 were also higher for mid‐June planting compared to mid‐May and early July plantings in both years. Across genotypes and years, mid‐June planting produced 13, 27, and 45% higher seed yield than late‐April, mid‐May, and early July plantings. Across planting dates, genotype NMSU‐15‐G1 had highest seed yield among all genotypes in both years; however, it did not differ significantly from cultivar Matador. Introduction lines and cultivar Matador took more days to reach various stages. The mid‐June planting showed early maturity. Guar planted under mid‐June planting appears to increase seed yield along with having early maturity in southern NM. Planting date had a significant effect on guar seed yield. Significant genotypic variation for seed yield was observed across planting dates. Planting dates and genotypes showed a significant interaction for guar seed yield. Mid‐June planting increased guar seed yield over other tested planting dates.