Hemp (Cannabis sativa L.) is an emerging high-value specialty crop that can be cultivated for either fiber, seed, or cannabidiol (CBD). The demand for hemp and its products has been consistently on the rise in the 21st century. The United States of America (USA) has reintroduced hemp and legalized its production as an agricultural commodity through the 2018 Federal Farm Bill. Although there is a renewed interest in the adoption of hemp due to the emerging market, its production in the United States (US) remains limited partly because of unclear agronomic guidance and fertilization recommendations. This review article provides information on the current agronomic management practices that are available in the literature and identifies the future research needs for cultivating this multipurpose crop to address the growing market demands. Hemp production could be beneficial if managed properly. Hemp fertilizer requirements vary in accordance with the type of hemp grown (seed, fiber, or CBD), soil, environmental conditions and requires a wide range of macro- and micronutrients. Integrating management practices in hemp cultivation intended to build soil health is promising since the hemp cropping system is suitable for crop rotation, cover cropping, and livestock integration through animal waste applications. Hemp also has significant environmental benefits since it has the potential to remediate contaminated soils through phytoremediation, convert high amounts of atmospheric CO2 to biomass through bio-sequestration, and hemp biomass for bioenergy production. This review identifies that most of the agronomic research in the past has been limited to hemp fiber and, to some extent, hemp seed but not CBD hemp. With the increase in the global markets for hemp products, more research needs to be conducted to provide agronomic guidelines for sustainable hemp production.

Limited water supplies in arid regions put constraints on agriculture. In arid New Mexico, greenhouse chile pepper production has the potential for water and nutrient savings. The objectives of this study were to (1) compare two capacitance sensors-(Hydra probes and 5TM) and one TDR CS616 sensor, (2) compute actual evapotranspiration (ETa) for drip-irrigated chile peppers for three water treatments, and (3) develop new crop coefficients (K c) for the three growing seasons in a greenhouse study. Three water treatments were (1) control where water was applied near the surface using two drip emitters, (2) partial root zone drying vertical (PRDv) where subsurface irrigation was applied at 20 cm depth from soil surface, and (3) partial root zone drying compartment (PRDc) where roots were divided into two compartments and irrigation was switched between compartments after 15 days. Sensor-generated volumetric water contents ( were correlated with the gravimetrically determined  and the new calibration coefficients improved the precision of estimates. From 2011 onward, irrigation amounts were adjusted to minimize deep percolation, and about 30% less water was applied in 2014 as compared to the 2011 growing season but no significant differences were observed in transpiration rate and leaf temperature. The ratio of intercellular to ambient CO 2 concentrations (Ci/Ca) was significantly correlated to transpiration rate and vapor pressure deficit in 2014 (P<0.05). ETa obtained from water balance and reference ET (ETr) from Penman-Monteith developed the K c for drip-irrigated greenhouse chile peppers for three growing seasons. The maximum values of K c were about 1.4 during 2013 and 1.2 during 2014. The 2011 growing season was shorter and the maximum K c were closer to one. Crop coefficients for greenhouse grown chile peppers varied with growing seasons and irrigation treatment. Irrigation scheduling can be done based on the soil moisture or K c for the known growing season. This study demonstrated the water saving potential of PRD.

Identifying the importance of soil biology in different land use systems is critical to assess the present conditions of declining soil (C) and global land degradation while regulating soil health and biogeochemical nutrient cycling. A study was undertaken in a mixed watershed comprising of different land use systems (agricultural, grassland, agroforestry, and eroded); situated in the Shiwalik region in the foot hills of the lower Himalayas in India, a fragile ecosystem susceptible to land degradation. Soil samples from 0–15 and 15–30 cm depths were collected from these land use systems and analyzed for a suite of different soil health indicators, including physio-chemical soil properties, aggregate stability, soil microflora, and the enzymatic activities that are critical for nutrient cycling. Principal component analysis was used to group different land uses and understand their association with soil microflora, enzyme activities, and soil physio-chemical properties. We found that a greater number of soil microflora and enzymatic activities were associated with grassland and agroforestry land use systems. Aggregate-associated soil C correlated well with the soil microflora under different land use systems studied. The biplots revealed that the fungal:bacterial ratio (2 × 103–0.1 × 103) was a robust indicator of C accumulation and soil health, and was in greater association with the agroforestry land use system. Random forest, a non-parametric statistical test, on average explained that 68% to 92% of the variability in soil microbial population was due to land use and other soil health properties. Overall, the biological soil health indicators used in this study demonstrated the fact that land use management systems that employ constant crop cover with minimal disturbance have the potential to improve soil sustainability and ecological functioning.

Amaranth (Amaranthus spp.) is an increasingly high-valued niche vegetable crop among small organic growers in North Carolina, due to its increasing demand among diverse immigrant groups. Production is however hampered by insect pests such as the flea beetle (FB), Disonycha glabrata (Coleoptera: Chrysomelidae), that cause significant yield reduction. Chemical insecticides are generally applied for pest control despite their known risks to health and the environment. Integrated pest management (IPM), which is a cost effective and environmentally friendly approach is still under-exploited in vegetable production by small growers. We studied IPM approaches, suitable for organic production of amaranth by screening nine amaranth varieties for resistance to the flea beetle (FB), D. glabrata, grown with, and without, mulch. D. glabrata population was 60% higher in plots with mulch compared to plots without. The amaranth varieties Molten fire and Green Callaloo recorded the lowest and the highest beetle population commensurate with low, and high leaf damage, respectively. Conversely, leaf yields in the mulched plots were 50% less than recorded in the zero-mulch counterpart, with Green Callaloo variety recording the lowest. These findings will serve as building blocks for a sustainable pest management plan that is appropriate for organic production of Amaranthus spp. in North Carolina.

Water saving, productivity, and quality of the chile pepper were evaluated under three irrigation treatments. Three drip irrigation treatments used were 1) control, where water was applied at the surface using two drip emitters; 2) partial root-zone drying vertically (PRDv), where subsurface irrigation was applied at 20 cm depth from soil surface; and 3) partial root-zone drying compartment (PRDc), where roots were divided into two compartments and irrigation was applied to one of the compartments on every alternate-day cycle for 15 days. Continuous measurements of soil water content were carried out during the growing seasons of 2013 and 2014, respectively. During both growing seasons, the stomatal conductance (gS) and net photosynthetic rates (Pn) were similar among all treatments including the control. In both PRD treatments, a higher rooting depth and root length density (RLD) than the control likely compensated for the water stress in dry soil zones by taking up more water from the water available parts of the root-soil system. In PRDc and PRDv treatments, 30% less water was applied than control without significant changes to plant stress expressed by stem water potential, plant height, capsaicinoid concentration, and yield. The increased irrigation water use efficiency (IWUE) demonstrated water saving potential of both PRD techniques for chile pepper production in water-limited arid environments.

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