Continuous Cotton Production Research Articles

Long−Term Fertilization Increased Nitrous Oxide Emissions from Croplands Reclaimed from Desert

Few studies have investigated how the reclamation of the desert to cropland affects soil nitrous oxide (N2O) emissions. A study site was initiated in 2005 at the southern Taklimakan Desert by establishing four fields along the desert−oasis ecotone. Three fields were reclaimed as croplands for continuous cotton (Gossypium hirsutum L.) production and received (1) high, (2) low, and (3) no fertilizer inputs and the fourth field remained as a native desert. Static-chamber monitoring of N2O flux was conducted from April 2019 to March 2021. N2O emissions occurred in cropland mainly after drip fertigation during the growing season. The two−year N2O emissions in the desert, no fertilizer, low fertilizer, and high fertilizer were 248, 670, 2232, and 3615 g N ha−1, respectively. The native desert was a weak source of N2O emissions, with the non−growing season emissions accounting for 66% of the annual emissions. N2O emissions from farmland mainly occurred over the growing season, accounting for 73−98% of the total annual emissions. The N2O flux was positively related to soil NO3−−N concentration and soil water−filled pore space (WFPS), highlighting the importance of soil N availability and moisture in affecting N2O emissions in extremely arid areas. Our results demonstrate that land reclamation from the desert to cropland significantly increased N2O emissions due to high nutrient inputs. Thus, appropriate fertilizer management in the reclaimed land is essential for maintaining yield, improving soil quality, and reducing N2O emissions for continuous cotton production.

Modeling the impacts of cover crops and no-tillage on soil health and cotton yield in an irrigated cropping system of the Texas Rolling Plains

An interest to grow cover crops is increasing in the semi-arid Texas Rolling Plains (TRP) region, where cotton ( Gossypium hirsutum L.) is a major cultivated crop. Under conservation tillage systems, cover crops are expected to enhance ecosystem services, including improved soil health and erosion reduction. However, there is a concern that cover crops could deplete soil water content and affect the subsequent cotton production. This study evaluated the efficacy of growing winter cover crops in a continuous cotton production system under irrigated conditions at Chillicothe, TX with the Denitrification Decomposition (DNDC) model. Treatments included: conventional tillage (CT), no-till (NT), no-till with mixed-species cover crop (Mixture), and no-till with winter wheat ( Triticum aestivum ) cover crop (Wheat) . The DNDC model was calibrated and validated against observed data from 2012 to 2020. Seed cotton yield prediction during model calibration had a percent bias (PBIAS) of 4.4 %, root mean square error (RMSE) of 385 kg ha −1 , r 2 of 0.55, d-index of 0.84, and a Nash–Sutcliffe model efficiency (NSE) of 0.92. Seed cotton yield during model validation had PBIAS of − 2.0 %, RMSE of 279 kg ha −1 , r 2 of 0.75, d-index of 0.93, and a NSE of 0.72. Simulated soil organic carbon (SOC) stock had a PBIAS of 8.6 % and 3 %, RMSE of 1.8 and 0.74 Mg ha −1 , r 2 of 0.92 and 0.98, d-index of 0.97 and 0.99, a NSE of 0.89 and 0.98 during model calibration and validation, respectively. Daily trends of simulated soil water content at 0–100 cm depth were within the acceptable range. Long-term simulations (25 years) revealed: (1) planting cover crops could accrue 11–19 % more SOC and 4–14 % more TN compared to no-cover crops, (2) cotton yield under cover crops was not significantly different from that under no-cover crops, (3) cover crop biomass increased immoblisation of nitrogen (N), which led to a decline in available N and hence, N-stress was simulated during the initial cotton growth period. In nutshell, results showed the potential of conservation management systems such as no-till and cover crops in improving soil health indicators without affecting cotton yields. • Simulated effect of mixture and winter wheat cover crops on seed cotton yield was not significant. • Cover crops sequestered 11–19 % more soil organic carbon (SOC) compared to no-cover crops. • Cover crops accrued 4–14 % more total nitrogen (TN) compared to no-cover crops. • Rate of SOC and TN accrual was highest under mixed species cover crop followed by winter wheat. • Soil N availability was declined in early stages of cotton due to increased N immobilization by cover crop biomass.

Variation in Bacterial Community Structure Under Long-Term Fertilization, Tillage, and Cover Cropping in Continuous Cotton Production.

Agricultural practices alter the structure and functions of soil microbial community. However, few studies have documented the alterations of bacterial communities in soils under long-term conservation management practices for continuous crop production. In this study, we evaluated soil bacterial diversity using 16S rRNA gene sequencing and soil physical and chemical properties within 12 combinations of inorganic N fertilization, cover cropping, and tillage throughout a cotton production cycle. Soil was collected from field plots of the West Tennessee Agriculture Research and Education Center in Jackson, TN, United States. The site has been under continuous cotton production for 38 years. A total of 38,038 OTUs were detected across 171 soil samples. The dominant bacterial phyla were Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, and Chloroflexi, accounting for ∼70% of the total bacterial community membership. Conventional tillage increased alpha diversity in soil samples collected in different stages of cotton production. The effects of inorganic N fertilization and conventional tillage on the structure of bacterial communities were significant at all four sampling dates (p < 0.01). However, cover cropping (p < 0.05) and soil moisture content (p < 0.05) only showed significant influence on the bacterial community structure after burn-down of the cover crops and before planting of cotton (May). Nitrate-N appeared to have a significant effect on the structure of bacterial communities after inorganic fertilization and at the peak of cotton growth (p < 0.01). Structural equation modeling revealed that the relative abundances of denitrifying and nitrifying bacteria were higher when conventional tillage and vetch cover crop practices were applied, respectively. Our results indicate that long-term tillage and fertilization are key factors increasing the diversity and restructuring the composition of bacterial communities, whereas cover cropping may have shorter-term effects on soil bacteria community structure. In this study, management practices might positively influence relative abundances of bacterial functional groups associated with N cycling. The bacteria functional groups may build a network for providing N and meet microbial N needs in the long term.

Soil acidification in a continuous cotton production system

AbstractEffects of nitrogen (N) fertilization on soil organic carbon (SOC) and total N are well established, but their effects on soil acidification and emerging soil health indicators such as labile N and carbon (C) pools are not adequately documented. This research evaluated soil N and C pools and soil pH with long‐term N management in continuous cotton (Gossypium hirsutum L.) production. Residual soil inorganic N, potentially mineralizable N and C, total N, SOC, pH, and electrical conductivity were measured after 17 yr of continuous N application. Comparison of five N rates (0, 56, 112, 168, and 224 kg ha–1) showed an increase in residual inorganic N pools and decrease in pH with an increase in N application rate, while other parameters did not change significantly. Soil acidification was significant with 168 and 224 kg N ha–1 rates. Soil pH dropped by 0.039 per kilogram increase in residual inorganic N. Optimizing N rate that minimizes residual inorganic N can reduce soil acidification.

Net return and risk analysis of winter cover crops in dryland cotton systems

AbstractWinter cover crop and no‐till are two promising conservation practices to reduce soil erosion and promote long‐term sustainability. This research evaluates the net returns of two different tillage methods and five cover crop treatments in dryland cotton (Gossypium hirsutum L.) production and identifies risk‐efficient tillage and cover crop management practices. Four‐year field experiments (2013−2016) were conducted for a continuous cotton production system under conventional tillage and no‐till without a cover crop, as well as no‐till with cover crops including winter wheat (Triticum aestivum L.), crimson clover (Trifolium incarnatum L.), Austrian winter field pea (Pisum sativum L.), hairy vetch (Vicia villosa Roth), and mixed cover crops. Results showed no statistical differences in lint yields (P = .98) or net returns (P = .82). No‐till with crimson clover decreased yield variation compared to conventional tillage, while hairy vetch and mixed cover crops increased yield variation. The average net returns were US$454 and $461 ha−1 for conventional tillage and no‐till without a cover crop, respectively. The average net returns ranged from $346 to $389 ha−1 for the cover crop treatments. Producers have a higher probability of getting a higher net return if switching from conventional tillage to no‐till. The risk analysis results showed that no‐till without a cover crop was the most preferred practice by risk‐neutral, somewhat and rather risk‐averse producers. For very and extremely risk‐averse producers, no‐till with crimson clover was the most preferred management practice.

Reclamation of desert land to continuous cotton cropping affects soil properties and microbial communities in the desert-oasis ecotone of Xinjiang, China

A large area of desert land in the desert-oasis ecotone in northwestern China is being reclaimed for continuous cotton production for several decades. However, little is known about the possible effect of reclamation and long-term monocultural cotton cultivation on soil properties and microbial communities in the desert-oasis ecotone area. Soil samples were collected from the 0–20-cm mineral soil from croplands that had been continuously planted cotton for 5, 25, and 50 years after reclamation, as well as a desert land (t = 0, before reclamation, used as the control). Soil physical and chemical properties, enzyme activities, and bacterial and fungal community diversities were determined. Soil organic carbon, total nitrogen, and enzyme activities increased up to 25 years after reclamation, and further monocultural cotton cropping was not beneficial to improve soil quality. Soil urease, alkaline phosphatase, and sucrase activities increased by 121~205%, 100~167%, and 206~719% in croplands as compared with the desert land, respectively, after reclamation with the highest value at 25 years of cotton cultivation. Bacterial richness and diversity increased from desert land to the 5-year-old cropland and then remained stable after 5 years of cotton cropping, and soil fungal richness and diversity were not affected by reclamation and cropping years. Crop rotation or fallow should be considered to maintain or improve soil quality over the long-term monocultural cropping.

Effects of continuous cropping with straw return on particulate organic carbon and Fourier transform infrared spectroscopy in cotton field

A long-term field experiment was conducted to investigate the effects of continuous cotton production years (0 as control, 5, 10, 15 and 20 years) and straw return on soil organic carbon (SOC) structure and stability by using Fourier transform infrared spectroscopy (FTIR) in Manas River valley of Xinjiang. The results showed that the relative peak intensity of polysaccharide and aromatics decreased with increasing continuous cropping years, whereas the aliphatic and alcoholic phenols relative peak intensity and the CH/C=C increased. The content of soil particulate organic carbon (POC) increased significantly in the 5-yr of cotton production farmland and then decreased with the increases of continuous cropping years. POC content was 5.11 times higher in 5-yr than that of the control. The content of mineral-bound organic carbon (MOC) was the highest in 10-yr farmland, being 1.84 times higher than that of the control. The highest value of the ratio of POC and MOC content (ω(POC)/ω(MOC)) was observed in 5-yr farmland. Together, long-term continuous cotton production with straw return led to SOC structure aliphatic and soil mineral binding increased the protection of organic matter, thus increasing the stability of soil organic matter.

Inorganic Phosphorus Distribution in Soil Aggregates Under Different Cropping Patterns in Northwest China

Accurate information on soil inorganic phosphorus (Pi) is crucial for the sustainable development of agriculture in arid regions. An experiment was conducted to investigate the effect of cropping patterns on Pi concentrations in soil aggregates from the 0–10 cm depth in northwest China. The three cropping patterns were as follows: continuous cotton (CC), corn-wheat rotation (CW), and tree-cotton intercropping (TC). The results showed that more than 89% of the soil mass was in the macroaggregates (> 0.25 mm) in all cropping patterns, indicating a good soil structure in the study area. Total Pi and available P concentrations were significantly higher in the TC > CW. Additionally, the O-P concentrations were enriched in the CC treatment. But, the Ca8-P, Al-P and Fe-P concentrations were significantly greater in CW and TC than in CC. These results suggested that continuous cotton production leads to plant available Pi (Ca8-P, Al-P, and Fe-P) convert into unavailable Pi forms (Ca10-P and O-P). The TC system had the greatest contribution to total P in > 0.25 mm aggregates (p < 0.05), suggesting TC had a greater capacity to supply soil P. TC may be an appropriate farming practice for maximum availability of P in arid farmland ecosystems.

Carbon dioxide mitigation potential of conservation agriculture in a semi-arid agricultural region

The Texas High Plains (THP) region is one of the largest upland cotton (Gossypium hirsutum L.) producing regions in the world. Cotton is a versatile crop with uses for both food and fiber products. Conservation management practices such as no-tillage and cover crops have been used to reduce wind erosion on the THP but are also associated with mitigating and reducing greenhouse gas (GHG) emissions from soil. Although row-crop agriculture has been linked to GHG emissions across the world, cotton production in the THP ecoregion has not been thoroughly evaluated for its contribution to GHG production. This research quantified the soil flux of carbon dioxide (CO2-C) from continuous cotton production systems on the THP after implementing three tillage practices: (1) no-till with a winter wheat cover crop (NTW); (2) no-till winter fallow (NT); and (3) conventional tillage winter fallow (CT). In addition, the timing of nitrogen fertilizer application was evaluated within each tillage system. Five N treatments were implemented: (1) an unfertilized control; (2) 100% pre-plant (PP); (3) 100% side-dressed (SD); (4) 40% PP 60% SD; and (5) 100% PP with a nitrogen stabilizer product (STB). Tillage practice affected CO2-C flux rates in spring 2016 and 2017 with the NTW system having greater CO2-C flux than the NT and CT systems. In summer 2017, the NTW system had a greater flux of CO2-C than the NT or CT systems. In fall/winter 2016, the NTW and CT systems had a greater CO2-C flux than the NT system. Cumulative emissions of CO2-C were affected by N treatment in 2016, with later season applications of N fertilizer increasing emissions compared to the STB treatment and the control. In 2017, cumulative emissions of CO2-C were greater in the NTW system than in the NT and CT system. However, a greater amount of CO2-C was assimilated by the wheat cover crop from the atmosphere than was lost from the soil which reduced net C losses from the system. With continued use of no-tillage and a cover crop, lower net soil CO2-C losses should result in a greater rate of soil organic C gain, positively impacting the sustainability of cotton production in the THP.

Duration of continuous cropping with straw return affects the composition and structure of soil bacterial communities in cotton fields.

Salinized land in the China's Xinjiang Region is being reclaimed for continuous cotton production. The specific objectives of this field study were (i) to compare bacterial composition and diversity in unfarmed (i.e., unreclaimed) and continuously (5, 10, 15, and 20 years) cropped soils and (ii) to explore correlations between soil properties and the bacterial communities identified by Illumina MiSeq sequencing. The results showed that bacterial species richness and diversity increased for 10-15 years and then declined when salinized land was reclaimed for cotton production. Proteobacteria and Firmicutes were the dominant phyla in unfarmed soil. Continuous cropping reduced the abundance of Firmicutes but increased that of Chloroflexi, Acidobacteria, and Actinobacteria. Cluster analyses showed that the greatest similarities in bacterial communities were between the 5- and 10-year treatments and between the 15- and 20-year treatments. Soil pH, electrical conductivity, alkali-hydrolyzable N, and available P were significantly correlated with bacterial community distribution. Overall, cotton production improved soil physicochemical properties and altered the structure and composition of soil bacterial communities compared with unfarmed soil. These positive effects began to decrease after 10-15 years of continuous cotton production.

Measuring Sustainable Cotton Production Using Total Factor Productivity

Continuous cotton (Gossypium hirsutum L.) production was examined using data from Alabama's long-term Old Rotation experiment (c. 1896). Index values were used to examine trends in productivity and sustainability for 95 yr. Treatments studied were those receiving (i) no N fertilizers and no winter legumes for 95 yr, (ii) only winter legumes as a source of N, and (iii) chemical fertilizer N. Three sets of index numbers were calculated from all inputs and outputs involved in the production systems: (i) total factor productivity (TFP), which accounts for an direct production inputs, but which does not consider production externalities; (ii) productivity relative to a base plot; and (iii) total social factor productivity (TSFP), which accounts for all direct production inputs as well as externalities of soil erosion and pesticide use. Viewed from the 95-yr perspective of the Old Rotation experiment, all three treatments fulfill at least one criterion required for a system to be considered sustainable. Output per unit of input is higher in 1991 than in 1896, even when externalities are valued. None of the systems showed a linear trend in output or TFP over the life of the experiment; productivity cycles are present in all three systems, despite a positive overall trend. An average annual rate of TSFP growth of 1.8%/yr was attained- Accounting for erosion and pesticide externalities reduced the annual productivity growth rate by 0.2%/yc The system that has neither an organic nor a chemical source of added N was less productive and less sustainable than the two other systems with a 0.3%/yr TSFP growth rate. The plots using organic and chemical sources of N had similar productivity impacts. Valuing soil erosion and pesticide externalities had only a modest effect on measured productivity. The most dramatic single event to affect the productivity of cotton farming was the introduction of the mechanical cotton picker. The impact of this technology was powerful enough to offset the effect of many other changes in the system.

Crop Rotation and Tillage Effects on Soil Water and Cotton Yield

AbstractThe Texas Southern High Plains is a major cotton (Gossypium hirsutum L.) producing area where a monoculture of conventionally tilled continuous cotton is thought to be causing a downward trend in yields. A factorial experiment with split plot design evaluated the main and interactive effects of (i) cotton‐wheat (Triticum aestivum L.)‐fallow rotation vs. continuous cotton, (ii) no tillage vs. conventional tillage, and (iii) furrow diking vs. no diking on cotton yield and soil water. Effects were determined for both dryland and irrigated production. Of the main factors considered, the cotton–wheat rotation had the greatest positive effect on yield and also on soil water variables. Rotation increased dryland and irrigated lint yields 12.6 and 12.8%, respectively. No tillage significantly increased yields (6.9 and 5.5% for dryland and irrigated, respectively) and enhanced seasonal soil water status. Yield increase due to diking was not statistically significant (P &gt; 0.05) under continuous cotton production or when wheat was rotated with cotton. The greatest cotton lint yield and soil water increases were obtained when no tillage was combined with the cotton–wheat rotation (20–25% increases). Percent yield increase was directly associated with improved soil water relations resulting from the cropping and tillage treatments.

Influences of nitrogen treatments and irrigation methods on soil chemical properties

Abstract Changes in soil chemical properties were investigated in conjunction with an ongoing study of fertility and irrigation relationships of cotton. Four irrigation methods and five nitrogen fertilization rates were the primary focus of the study. The four irrigation regimes studied were: high frequency center pivot, low frequency center pivot, furrow irrigated, and unirrigated. Nitrogen rates were 0, 30, 60, 90, and 120 lb N/A. Soil samples were collected from each plot in 6‐in‐ increments to a depth of 24 in. in 1982 and again in 1986 after four years of continuous cotton production. The soil samples were analyzed for pH, organic matter (OM), P, K, electrical conductivity (EC), and NO3 ‐‐N. All background soil characteristics were found to vary with depth with the exception of NO3 ‐‐N. The follow‐up sampling and testing in 1986 showed significant differences in soil properties as a function of irrigation, N‐fertilization, depth, and their interactions. Nitrates were accumulated in the 18 to 24‐in. depth under high (120 lb N/A) fertilization, and in the 0 to 6‐in. depth under the four lower treatments (0, 30, 60, and 90 lb N/A). Soil pH was highest in the furrow and high frequency center pivot irrigated regimes and lowest in the unirrigated regime. Soil pH also decreased with depth. Electrical conductivity of the soil was highest in the high frequency regime and not significantly different among the other three irrigation methods. The 0M content of the soil was greatest in the high frequency regime but not significantly different in the low frequency, furrow, or unirrigated blocks. Soil 0M was found to decrease with depth through 18 in. in all cases. The P and K status of the soil was not changed as a result of the N fertilization or irrigation treatments.

Populations of bacteria and actinomycetes associated with sclerotia ofPhymatotrichum omnivorum buried in Houston black clay

Sclerotia ofPhymatotrichum omnivorum (Shear) Duggar (the causal agent of root rot of cotton) were produced in the laboratory and then buried at a depth of 45 cm at three sites in Texas situated on Houston black clay soils with various cropping histories. The sites included a native grassland prairie, a field in continuous cotton production, and a field in which cotton, corn, and sorghum were grown in rotation. Samples of sclerotia were retrieved monthly over a 12 month period. Populations of bacteria and actinomycetes were enumerated using dilution-plate techniques and isolates were screened (in vitro) for their ability to produce substances inhibitory toP. omnivorum. The sclerotia supported large numbers of bacteria (including fluorescent pseudomonads) and actinomycetes. Numbers associated with sclerotia ranged from 106–109 cells per gram of sclerotia plus adherent soil and were 2–3 orders of magnitude greater than numbers from soil at the same depth but free of sclerotia. Bacteria and actinomycetes antagonistic toP. omnivorum were isolated from sclerotia buried at each of the three sites. Up to 26% of the isolates inhibited growth ofP. omnivorum.