The ability of soil to retain water under drought and other extreme hydrological events is critical to the sustainability of food production systems and preserving soil ecosystem services. We investigated the impact of biochar on water retention properties in California agricultural soils in a series of column, lab incubation, and field studies. Results from studies based on similar variables (soil, biochar) were used to demonstrate the impact of biochar on soil-water relations at different scales. The influences of biochar type (softwood, 600–700 °C, low surface area; walnut shell, 900 °C, high surface area), application rate (0, 0.5, 1% wt.), and particle diameter (0–0.25, 0.25–0.5, 0.5–1, 1–2 mm) were investigated. Only the higher surface area biochar increased the field capacity of a sandy soil. Neither biochar, altered the field capacity of the higher clay content soil. The walnut shell biochar with 1–2 mm particle diameter was more effective at increasing field capacity in sandy soils compare to smaller biochar size fractions. Neither biochar affected the wilting point in either soil. Neutron imaging was used to explore potential mechanisms involved in water retention by observing the spatial and temporal distribution of water in and surrounding biochar particles (~ 2 mm diameter). After wetting, water retained in the internal pores of biochar was continuously released to surrounding space (~ 2.2 mm sphere) during a 7-day air drying at room temperature, suggesting that soil water retention is improved via the biochar's intraparticle structure. In the field trial, (6 yr., corn-tomato rotation), neither walnut shell biochar amendment (10 t/ ha, equivalent to 0.5% wt. in lab scale experiments) nor agricultural management practices (organic, conventional) altered the water retention capacity of a silty clay loam soil. These data suggest that biochars with a high pore volume can temporarily increase the field capacity and plant available water in a coarse-textured soil, until biochar internal pores are filled by clay and soil organic matter. Our results suggest that biochar can have a limited impact on soil water retention when biochar pore volume is low, or soil texture is fine. High dosage (≥10 t/ha) of high pore volume biochar with bulky particle size (≥1 mm) can improve water retention of coarse-textured soil with limited capacity of water storage and may improve soil's resilience during hydrological extremes.

Biochar is increasingly been used as a soil amendment to improve water-holding capacity, reduce nutrient leaching, increase soil pH, and also as a means to reduce contamination through sorption of heavy metals or organic pollutants. The sorption behavior of three phenylurea herbicides (monuron, diuron and linuron) on five biochars (Enhanced Biochar, Hog Waste, Turkey Litter, Walnut Shell and Wood Feedstock) and an agricultural soil (Yolo silt loam) was investigated using a batch equilibration method. Sorption isotherms of herbicides to biochars were well described by the Freundlich model (R(2) = 0.93-0.97). The adsorption KF values ranged from 6.94 to 1306.95 mg kg(-1) and indicated the sorption of herbicides in the biochars and Yolo soil was in the sequence of linuron > diuron > monuron and walnut shell biochar > wood feedstock biochar > turkey litter biochar > enhanced biochar > hog waste biochar > Yolo soil. These data show that sorption of herbicides to biochar can have both positive (reduced off-site transport) and negative (reduced herbicide efficacy) implications and specific biochar properties, such as H/C ratio and surface area, should be considered together with soil type, agriculture chemical and climate condition in biochar application to agricultural soil to optimize the system for both agricultural and environmental benefits.

Adding manure to croplands restores carbon and nutrients in depleted soils, while addressing a waste disposal need. This practice depends on the abundance and activity of microbial communities to break down manure inputs, which provide carbon for microbial growth and release nutrients for plant and microbial uptake. In a 2-year field study, we measured changes to soil physicochemical properties and microbial community composition in a conventional rotation of summer sileage corn and winter wheat. Three ratios of manure to mineral N fertilizer were used: all manure (100% of plant N from manure), mixed (50% plant N from by manure and 50% from mineral fertilizer), and all mineral (100% plant N from mineral fertilizer). Yields of corn and wheat were similar across treatments. Soil microbial community dissimilarity increased with higher ratios of application, suggesting a dose-dependent relationship between manure application and microbial community composition. Both microbial biomass and dissolved organic carbon showed the greatest response immediately following manure application, then decreased until the next application. The Shannon index increased shortly after manure application, with the largest increase observed in soils receiving manure input. Many of the taxa that increased in relative abundance following manure application were specifically taxa known to be present in manure and not common or present in soil before manure application. Microbial community changes following manure application were transitory, indicating that without continual inputs of resources, these alterations are not maintained. This was in contrast to microbial biomass which slowly increased in size over the 2-year study period. Better understanding of how manure interacts with microbial communities will help in developing better nutrient management practices and help reduce our reliance on mineral fertilizers.

Soil organic amendments in agricultural production can benefit crop production and a wide range of soil properties, including soil aggregation. Soil aggregate formation is largely driven by microbial activities, and can in-turn influence microbial communities by generating distinct microbial habitats, as well as associated impacts on water and nutrient dynamics. We investigated the long-term effects of two fertilizer management strategies (poultry manure compost vs. mineral fertilizer) and biochar amendment (0 vs. 10 t ha−1 walnut shell biochar, 900 °C pyrolysis temperature, by-product of gasification) on soil aggregation, soil organic C, and microbial community dynamics in water-stable aggregate fractions in corn-tomato rotations. Using wet-sieving, soils (0–15 cm) were divided into four size fractions: large macroaggregates (2000–8000 μm), small macroaggregates (250–2000 μm), microaggregates (53–250 μm) and silt and clay (<53 μm) for calculation of mean weight diameter in both 2014 and 2018. The total C and microbial community composition and abundance within each fraction were evaluated in 2018. Across all treatments, six years of continuous compost application maintained soil aggregate stability and C storage by increasing soil microbial biomass and associated dissolved organic C. Bacterial and fungal populations under compost treatments were significantly higher than under mineral fertilizer treatments based on 16S rRNA gene copy number and internal transcribed spacer (ITS) abundance, which likely contributed to the formation and maintenance of macroaggregates in compost treatments. Interestingly, continuous application of manure compost may increase microbial available C sources by increasing the abundance of bacteria with the potential to degrade aromatic C as predicted from 16S sequences. Soil under the mineral fertilizer treatment showed decreases in the proportion of large macroaggregates, bulk soil C, and aggregate-associated C storage compared to the compost treatment. The application of highly recalcitrant walnut shell biochar had limited long-term impacts on soil aggregation and C dynamics, likely due to its lack of microbially-available C and limited interaction with the soil environment. Our results indicate that continuous compost inputs maintained soil structure and associated physical stabilization of SOM by enlarging soil microbial available C pool, higher soil microbial biomass, and increasing aggregate formation. The soil aggregate structure, in-turn, generated diverse habitats and altered soil microbial communities. Compost inputs, in addition to or in partial replacement of mineral fertilizer inputs, can provide valuable microbial-driven ecosystem services, such as carbon storage and soil structure, while still providing fertility for crop growth.

Background

To evaluate the safety and tolerability of docetaxel/carboplatin regimen in the post-operative setting of patients with non-small cell lung cancer (NSCLC).

Methods

Enrolment of 133 patients with stage Ib - IIIa NSCLC was undertaken in an open-label, single arm study to assess the safety and tolerability of docetaxel (75 mg/kg) and carboplatin (AUC 5.5) administered for 3 cycles after resection for curative intent. The primary endpoint of the study was safety, as reflected by a febrile neutropenia rate of <10%. Other endpoints assessed protocol compliance and the impact of minimally invasive surgical technique.

Results

Patient accrual was completed at 1 center in the US and 10 centers in China in <6 months. Febrile neutropenia complicated treatment in 12 patients (9.0%), below the predetermined safety threshold of 14 patients. Four VATS and 8 open thoracotomy patients experienced febrile neutropenia (P=0.26). Completion of the three-cycle adjuvant regimen was achieved in 86% (95% CI, 77-95%) of patients. Sixty-two of 66 VATS patients compared to 53 of 67 open thoracotomy patients received all three doses according to protocol (P<0.01). Thirteen serious adverse events (9.8%) and no deaths were attributed to the study regimen.

Conclusions

In this rapidly accrued study, docetaxel and carboplatin were well-tolerated in the adjuvant treatment of NSCLC. Adjuvant treatment compliance was higher among patients undergoing a minimally invasive surgical approach. (ClinicalTrials.gov number NCT00883675).