Biodegradable plastic mulch is potentially a suitable alternative to conventional polyethylene mulch because of the limited disposal options of the latter. However, biodegradable plastic mulch must perform better or comparably to polyethylene mulch to be widely adopted. Gas exchange and soil microclimate are important factors impacted by the use of plastic mulch, which in turn have implications on crop productivity. A controlled-environment study was established in a greenhouse to assess gas exchange and soil microclimate dynamics under biodegradable plastic, polyethylene, and paper mulches with and without planting holes, as well as the impact of the mulches on the growth of sweet corn (Zea mays). A no-mulch condition was included as control. In addition, we monitored CO2 concentrations in the vicinity of planting holes (chimney effect) in a greenhouse and agricultural field conditions under sweet corn production. The plastic mulches (both biodegradable plastic and polyethylene mulches) decreased the soil O2concentration to a minimum of 181–183 mmol mol-1, and when compared to the no-mulch, the plastic mulches reduced water loss within 50 days by 35–68 mm. The paper mulch inhibited light penetration more than did the plastic mulches. There was an increase in the CO2 concentration at 2.5 cm above the planting holes in the plastic mulches compared to that under the no-mulch. However, the differences were not discernible at 15 cm above the ground. Consequently, we did not observe significant impacts on the growth of sweet corn, possibly, because the canopy height of sweet corn was more than 15 cm within a few days after planting. Overall, the plastic mulches did not reduce O2 concentration below 100 mmol mol-1, the minimum level in which plant growth becomes impaired. Also, the often reported improved growth of sweet corn from plastic mulching could be attributable to other factors, such as weed control, reduced water loss, and early season soil warming, rather than elevated CO2 concentrations and fluxes in the vicinity of planting holes. Highlights- Gas exchange and soil microclimate dynamics under biodegradable plastic, polyethylene, and paper mulches were assessed - Elevated CO2 levels were observed near planting holes of plastic mulches (both biodegradable and polyethylene) - The plastic mulches inhibited O2 exchange, but not to a level that could impair plant growth - Polyethylene mulch conserved soil water better than biodegradable plastic and paper mulches - Paper mulch inhibited light penetration better than plastic mulches
Plastic mulch films are used globally in crop production but incur considerable disposal and environmental pollution issues.Biodegradable plastic mulch films (BDMs), an alternative to polyethylene (PE)-based films, are designed to be tilled into the soil where they are expected to be mineralized to carbon dioxide, water and microbial biomass.However, insufficient research regarding the impacts of repeated soil incorporation of BDMs on soil microbial communities has partly contributed to limited adoption of BDMs.In this study, we evaluated the effects of BDM incorporation on soil microbial community structure and function over two years in two geographical locations: Knoxville, TN, and in Mount Vernon, WA, USA.Treatments included four plastic BDMs (three commercially available and one experimental film), a biodegradable cellulose paper mulch, a non-biodegradable PE mulch and a no mulch plot.Bacterial community structure determined using 16S rRNA gene amplicon sequencing revealed significant differences by location and season.Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA where differences were observed between BDMs and no-mulch plots.Extracellular enzyme rate assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDMs and PE treatments.Overall, BDMs had comparable influences on soil microbial communities to PE mulch films.
Nitrogen (N) deficiency limits the net carbon assimilation rate (AN), but the relative N sensitivities of photosynthetic component processes and carbon loss mechanisms remain relatively unexplored for field-grown cotton. Therefore, the objective of the current study was to define the relative sensitivity of individual physiological processes driving N deficiency-induced declines in AN for field-grown cotton. Among the potential diffusional limitations evaluated, mesophyll conductance was the only parameter substantially reduced by N deficiency, but this did not affect CO2 availability in the chloroplast. A number of metabolic processes were negatively impacted by N deficiency, and these effects were more pronounced at lower leaf positions in the cotton canopy. Ribulose bisphosphate (RuBP) regeneration and carboxylation, AN, and gross photosynthesis were the most sensitive metabolic processes to N deficiency, whereas photosynthetic electron transport processes, electron flux to photorespiration, and dark respiration exhibited intermediate sensitivity to N deficiency. Among thylakoid-specific processes, the quantum yield of PSI end electron acceptor reduction was the most sensitive process to N deficiency. It was concluded that AN is primarily limited by Rubisco carboxylation and RuBP regeneration under N deficiency in field-grown cotton, and the differential N sensitivities of the photosynthetic process and carbon loss mechanisms contributed significantly to photosynthetic declines.
Brassica carinata is a non-food industrial oilseed crop that can be grown in the winter in the southeast US without impacting food, feed, or fiber crops. Carinata is a low carbon advanced renewable fuel feedstock and a good source of animal protein. Carinata research in the SE US through a public-private partnership has developed a comprehensive body of knowledge regarding carinata agronomics, life cycle analysis, best management practices and economics. This article aims to help growers and others interested in carinata to understand its biology, agronomy, and production aspects.
Growers rely on nutrient sufficiency ranges (NSRs) after plant tissue analysis to inform timely nutrient management decisions. The NSRs are typically established from survey studies across multiple locations, which could be confounded by several abiotic and biotic factors. We conducted field studies in 2020, 2021, and 2022 to validate the lower thresholds of the NSRs for corn (Zea mays) at the early growth stage as reported in the Southern Cooperative Series Bulletin #394. We induced various corn nutritional levels by making different nutrient application rates. If the NSRs are valid, samples within the same replication that satisfy the NSRs of all nutrients should have similar biomass accumulation. The results showed that the NSRs were not valid under the conditions tested. In total, 47.6% of the samples satisfied all the lower thresholds of the NSRs, and 25.4% of those samples had relative biomass <50%, with relative biomass even as low as 24.2% observed. Moreover, 9.6% of the total samples had P and Cu levels that failed to meet the lower threshold but still had relative biomass ≥75%. The findings highlight the sensitivity of corn to nutrient imbalance and the need to optimize nutrient diagnostic methods at the early growth stage.
Camelina ( Camelina sativa L. Crantz) is an oilseed crop with the potential for dryland crop production in the Great Plains. However, pod shattering may cause significant yield losses. We determined the impact of different harvest times on camelina seed yield (SY), water use efficiency, protein and oil content, and estimated biodiesel yield. Spring (Blaine Creek) and winter (BX WG1) camelina cultivars were harvested at three different stages, corresponding to the three‐digit Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scales of 805 (early harvest; 50% ripe pods), 807 to 808 (mid‐harvest; 70–80% ripe pods), and 809 (late harvest; >90% ripe pods). In addition, different harvest methods were assessed to identify and quantify other sources of yield loss. Seed moisture contents at early, mid, and late harvests were 14.2, 9.8, and 6.8%, respectively. On average, the SY of early harvest was 9.5 and 23.6% greater than the mid‐ and late harvests, respectively. Total seed loss incurred during direct‐combine harvest was 11.7%, which was attributable to the mechanical disturbance imposed on the pods and the combine settings. Camelina seed oil content was greatest at mid‐harvest, but the estimated biodiesel yield was not significantly different between the early and mid‐harvests. In general, direct combining when 75% of camelina pods are ripe will provide a balance between SY loss and the seed protein and oil contents.
