Heavy metals and metalloids (HMs) are environmental pollutants, most notably cadmium, lead, arsenic, mercury, and chromium. When HMs accumulate to toxic levels in agricultural soils, these non-biodegradable elements adversely affect crop health and productivity. The toxicity of HMs on crops depends upon factors including crop type, growth condition, and developmental stage; nature of toxicity of the specific elements involved; soil physical and chemical properties; occurrence and bioavailability of HM ions in the soil solution; and soil rhizosphere chemistry. HMs can disrupt the normal structure and function of cellular components and impede various metabolic and developmental processes. This review evaluates: (1) HM contamination in arable lands through agricultural practices, particularly due to chemical fertilizers, pesticides, livestock manures and compost, sewage-sludge-based biosolids, and irrigation; (2) factors affecting the bioavailability of HM elements in the soil solution, and their absorption, translocation, and bioaccumulation in crop plants; (3) mechanisms by which HM elements directly interfere with the physiological, biochemical, and molecular processes in plants, with particular emphasis on the generation of oxidative stress, the inhibition of photosynthetic phosphorylation, enzyme/protein inactivation, genetic modifications, and hormonal deregulation, and indirectly through the inhibition of soil microbial growth, proliferation, and diversity; and (4) visual symptoms of highly toxic non-essential HM elements in plants, with an emphasis on crop plants. Finally, suggestions and recommendations are made to minimize crop losses from suspected HM contamination in agricultural soils.

Heavy metals and metalloids (HMs) are environmental pollutants, most notably cadmium, lead, arsenic, mercury, and chromium. When HMs accumulate to toxic levels in agricultural soils, these non-biodegradable elements adversely affect crop health and productivity. The toxicity of HMs on crops depends upon factors including crop type, growth condition, and developmental stage; nature of toxicity of the specific elements involved; soil physical and chemical properties; occurrence and bioavailability of HM ions in the soil solution; and soil rhizosphere chemistry. HMs can disrupt normal structure and function of cellular components and impede various metabolic and developmental processes. This review evaluates: (1) HM contamination in arable lands through agricultural practices, particularly due to chemical fertilizers, pesticides, livestock manures and compost, sewage-sludge based biosolids, and irrigation; (2) factors affecting the bioavailability of HM elements in the soil solution, and their absorption, translocation, and bioaccumulation in crop plants; (3) mechanisms by which HM elements directly interfere with the physiological, biochemical, and molecular processes in plants with particular emphasis on the generation of oxidative stress, inhibition of photosynthetic phosphorylation, enzyme/protein inactivation, genetic modifications, and hormonal deregulation, and indirectly through inhibition of soil microbial growth, proliferation, and diversity; and (4) visual symptoms of highly toxic non-essential HM elements in plants with an emphasis on crop plants. Finally, suggestions and recommendations are made to minimize crop losses from suspected HM contamination in agricultural soils.

A study was conducted in an irrigated arid agroecosystem in southwestern USA, to compare two conservation tillage systems (strip tillage (ST) and no-tillage (NT)) to conventional, plow-based tillage (PT) system. Corn silage (Zea mays L.) was planted in this trial. Growth parameters (plant population and height) of corn silage were measured during the season and yield was evaluated at harvest. Soil physical measurements assessed included mean weight diameter of dry aggregates, wet aggregate stability, and penetrometer resistance. While soil biological measurements included total microbial biomass, diversity index (DI), total bacteria biomass, total fungi biomass (TFB), arbuscular mycorrhizae fungi (AMF), and total saprophytes. Results showed that plant population and silage yield at 65% moisture content were not significant with tillage during both trial years. Soil physical parameters were mostly not significant with tillage, while three out of the six biological measurements (DI, TF, and AM) were significant with tillage at p ≤ 0.05. No-tillage had higher DI and TFB than the ST, but not different from PT, while AMF was significantly higher in PT than ST, but not different from NT. The study demonstrates that farmers in the study region can adopt conservation tillage without yield losses during the early years of transition.

Broadleaf (Plantago major L.) and buckhorn plantain (Plantago lanceolata L.) are perennial weeds that are notoriously difficult to control in alfalfa cropping systems. Sharpen^® (saflufenacil) herbicide has been registered for broadleaf weed control in dormant alfalfa, although it has not been evaluated on plantain control. Field and greenhouse experiments were conducted to determine the efficacy of saflufenacil on plantain control with assessments of damage to alfalfa and effects on yield. In the greenhouse, applications of saflufenacil alone caused greater injury to both broadleaf and buckhorn plantain compared to the non-treated control (NTC). Additionally, applications of saflufenacil in combination with other herbicides (imazethapyr or imazamox) caused the greatest amount of injury to both broadleaf and buckhorn plantain compared to all other commercially available herbicide treatments. However, this injury was not enough to effectively control the weeds and prevent recovery and regrowth over time. In the field, alfalfa did not exhibit damage symptoms, or have reduced yield when treated with saflufenacil compared to the NTC. This research indicates that applications of saflufenacil provided temporary injury throughout the duration of the study to both broadleaf and buckhorn plantain with few negative effects to alfalfa in the field.

Reducing tillage has become necessary in irrigated, arid cropping systems in southwestern USA, to address soil degradation and erosion problems associated with intensive soil tillage. A study was conducted in arid southwestern USA, to compare a reduced tillage method (strip tillage) to two conventional tillage methods (plow tillage and raised bed tillage) for irrigated upland cotton (Gossypium hirsutum) production. Strip tillage (ST) was established in a single pass by a strip tillage equipment, while the plow tillage (PT) consisted of plowing, disking the soil twice, subsoiling and harrowing. The raised bed tillage (BT) consisted of all the tillage operations under PT method, with an additional tillage event to shape the beds. Crop and soil parameters were assessed during the growing seasons. Soil physical and biological measurements were assessed at the beginning of the trial before planting, and at the end of each cropping season. Results show no significant differences in cotton yield and fiber quality parameters under the tillage systems tested. Out of the soil physical measurements assessed, the cone index (CI) significantly differed with tillage systems during the mid-season assessments, with BT generally having better CI than ST and PT. Other physical measurements were not significant with tillage, but significantly declined over time irrespective of tillage treatments. Out of the soil biological measurements assessed, the total fungal biomass and the arbuscular mycorrhizae fungi biomass were significant with tillage, with ST and BT having higher measurements than PT. In contrast to soil physical measurements that declined, most of the soil biological measurements improved over time. Comparing some soil biological measurements at the beginning to the end of the trial across the tillage treatments, the total microbial biomass increased from 714 to 3565 ng/g, the total bacterial biomass increased from 321 to 1478 ng/g, and the total fungal biomass increased from 84 to 436 ng/g. This study shows that ST can perform adequately for sustainable cotton production in an irrigated arid region of United States.

A weed garden was constructed to quantify and improve identification skills among clientele. The garden was planted with over 100 weed species based on surveys on problematic weeds. The weed garden proved useful for introducing additional hands-on learning activities into traditional lecture-based seminars. Through seminar and field day attendee feedback, data were gathered on weeds commonly misidentified. The data reflected the need to continue focusing education efforts on weed identification and to increase training on weeds commonly misidentified. Through continued use of the weed garden, Extension specialists can enhance clientele identification skills and aid in developing effective weed management strategies.