Hyperspectral imaging for estimating leaf, flower, and fruit macronutrient concentrations and predicting strawberry yields.

Managing the nutritional status of strawberry plants is critical for optimizing yield. This study evaluated the potential of hyperspectral imaging (400-1,000 nm) to estimate nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) concentrations in strawberry leaves, flowers, unripe fruit, and ripe fruit and to predict plant yield. Partial least squares regression (PLSR) models were developed to estimate nutrient concentrations. The determination coefficient of prediction (R2P) and ratio of performance to deviation (RPD) were used to evaluate prediction accuracy, which often proved to be greater for leaves, flowers, and unripe fruit than for ripe fruit. The prediction accuracies for N concentration were R2P = 0.64, 0.60, 0.81, and 0.30, and RPD = 1.64, 1.59, 2.64, and 1.31, for leaves, flowers, unripe fruit, and ripe fruit, respectively. Prediction accuracies for Ca concentrations were R2P = 0.70, 0.62, 0.61, and 0.03, and RPD = 1.77, 1.63, 1.60, and 1.15, for the same respective plant parts. Yield and fruit mass only had significant linear relationships with the Difference Vegetation Index (R2 = 0.256 and 0.266, respectively) among the eleven vegetation indices tested. Hyperspectral imaging showed potential for estimating nutrient status in strawberry crops. This technology will assist growers to make rapid nutrient-management decisions, allowing for optimal yield and quality.

Combined effects of biochar and fertilizer applications on yield: A review and meta-analysis.

The use of biochar is changing, and the combined application of biochar with fertilizer is increasingly gaining acceptance. However, the yield gains results reported in the existing literature through the co-application of fertilizer with biochar are conflicting. To resolve this, we utilized a meta-analysis of 627 paired data points extracted from 57 published articles to assess the performance of the co-application of biochar and fertilizers on crop yield compared with the corresponding controls. We also studied the impact of biochar characteristics, experimental conditions, and soil properties on crop yield. Our analysis showed that individually, biochar and inorganic fertilizer increased crop yield by 25.3% ± 3.2 (Bootstrap CI 95%) and 21.9% ± 4.4, respectively. The co-application of biochar with both inorganic and organic fertilizers increased crop yield by 179.6% ± 18.7, however, this data needs to be treated with caution due to the limited dataset. The highest yield increase was observed with amendments to very acidic soils (pH ≤5), but the benefits of biochar were not affected by the rate and the time after the application. In addition, the effects of biochar are enhanced when it is produced at 401-500 °C with a C:N ratio of 31-100. Our results suggest that the co-application of biochar with either inorganic and/or organic fertilizers in acidic soils increase crop productivity compared to amendment with either fertilizer or biochar. Our meta-analysis supports the utilization of biochar to enhance the efficiency and profitability of fertilizers.

Biochar compound fertilisers increase plant potassium uptake 2 years after application without additional organic fertiliser.

Biochar compound fertilisers (BCFs) are an emerging technology that combine biochar with nutrients, clays and minerals and can be formulated to address specific issues in soil-plant systems. However, knowledge of BCF performance over consecutive crops and without re-application is limited. This study aims to assess the residual effect of organic BCFs soil-plant nutrient cycling 2 years after application and without additional fertiliser inputs. We applied BCFs and biochar with organic fertiliser amendments and established a crop of ginger and a second crop of turmeric (Curcuma longa) without re-application or additional fertilisation. All treatment formulations included bamboo-biochar and organic fertiliser amendments; however, two novel BCFs were formulated to promote agronomic response in an intensive cropping system. We report here on the effect of treatments on soil and plant macronutrient and micronutrient cycling and turmeric growth, biomass and yield at harvest. Both BCFs (enriched (10 t ha-1) and organo-mineral biochar (8.6 t ha-1) increased foliar K (+155% and +120%) and decreased foliar Mg (-20% and -19%) concentration compared with all other treatments, suggesting antagonism between K and Mg. Plants were limited for K, P and B at harvest but not N, Ca or Mg. Foliar K was dependent on the biochar formulation rather than the rate of application. Biochar-clay aggregates increased K retention and cycling in the soil solution 2 years after application. Clay blended BCFs reduced K limitation in turmeric compared to biochar co-applied with organic amendments, suggesting these blends can be used to manage organic K nutrition. All formulations and rates of biochar increased leaf biomass and shoot-to-root ratio. Novel BCFs should be considered as an alternative to co-applying biochar with organic fertiliser amendments to decrease application rates and increase economic feasibility for farmers. Applying BCFs without re-application or supplementary fertiliser did not provide sufficient K or P reserves in the second year for consecutive cropping. Therefore, supplementary fertilisation is recommended to avoid nutrient deficiency and reduced yield for consecutive organic rhizome crops.

Effects of biochar, compost, and biochar-compost on soil total nitrogen and available phosphorus concentrations in a corn field in Papua New Guinea.

Replenishing soil nutrient particularly total nitrogen (TN) and available phosphorus (P) is important to sustain soil health for food production. Organic amendments such as compost and biochar are commonly applied to improve soil nutrient retention especially N and P. In farms, biochar is usually applied once followed by applying other organic amendment applied in their full rates. Both form and rate of organic amendments can affect soil nutrient concentrations particularly in short term. This study aimed to examine the effects of compost and mixture of compost with biochar (both at full rates) on soil nutrient concentrations in short term. A randomised complete block filed experiment with eight replicates was used for this study. The effects of biochar (5 t/ha) only, compost (at the rates of 10 t/ha, 25 t/ha and 35 t/ha) and biochar mixed with compost (5 t/ha and 10 t/ha, respectively) on soil nutrient concentrations compared with control were explored in a corn field. Compost treatment at the rate of 35 t/ha had significantly higher TN, available P, calcium (Ca) and iron (Fe) compared with other treatments and control. Soil potassium (K) levels remained unchanged among all treatments. Biochar only treatment had significantly higher available P and Ca concentrations compared with biochar mixed with compost treatment. Compost application at higher rate (35 t/ha) proved best practice to significantly increase TN and available P concentrations in short term. Significantly higher available P concentration in biochar only treatment compared with the biochar mixed with compost treatment could have been associated with stimulation of P immobilisation when biochar was mixed with compost. Our results indicated that the form and rate of organic amendments in short term cropping systems are important to be considered while applying to a volcanic soil to ensure N and P availability for plants are not compromised.

Short-term application of mulch, roundup and organic herbicides did not affect soil microbial biomass or bacterial and fungal diversity.

Application of synthetic herbicides is currently the most widely used and cost-effective methods to assist with revegetation programs. However, the effects of short-term application of herbicides such as Roundup®, acetic acid, BioWeed™ and Slasher® as compared with mulch, on soil microbial biomass and microbial diversity remain unknown. This study examined the effects of short-term herbicide application on soil microbial biomass, C:N ratio, and fungal and bacterial communities at months 2 and 8 following initiation of treatment application. No effects of treatments on soil pH, C:N and microbial biomass were found. No segregation among treatments in the community structure of bacteria and fungi was observed. However, the fungal phylum Basiodiomycota had one unidentified class, which was only found in the mulch treatment, suggesting the C quality in the mulch treatment may differ compared with the other treatments. The dry and hot conditions experienced throughout the study period may have resulted in fast degradation of the herbicides and may have minimised the impacts of the herbicides on microbial diversity and community structure. Given that the research was undertaken at a single site and over only a short time frame, the results should be extrapolated with caution. Herbicides may have greater impact with long-term use. Future research will need to assess the revegetation success of each treatment and determine if the observed change in Basidiomycota profile and C quality identified in this study becomes significant over the long-term. We hypothesise that mulching may be a preferred treatment to facilitate weed control in riparian zone revegetation.