Edited by: Kwame Agyei Frimpong, University of Cape Coast, Ghana
Reviewed by: Benedicta Essel Ayamba, Soil Research Institute, Council for Scientific and Industrial Research (CSIR), Ghana; Mukesh Kumar Awasthi, Northwest A&F University, China
This article was submitted to Land, Livelihoods and Food Security, a section of the journal Frontiers in Sustainable Food Systems
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Bioplant is a liquid soil conditioner that contains a consortium of beneficial fungi and bacteria manufactured by Artemis and Angel Company Limited in Bangkok. Bioplant is purported to stimulate beneficial microbial activity in soil and hence increase crop yield. However, the efficacy of Bioplant has not been evaluated on Ghanaian soils. A screen house trial was consequently conducted to evaluate the efficacy or otherwise of Bioplant on the yield of lettuce in a Rhodic Kandiustalf amended with or without compost. The soil was mixed with compost at 20 parts soil to 80 parts compost and 60 parts soil to 40 parts compost (v/v) and potted in 1.7-L pots. There was another potted soil with no compost amendment. To each of these potted soils, Bioplant was applied at four rates, viz., zero, half the manufacturer's recommended rate, the manufacturer's recommended rate, and twice the manufacturer's recommended rate, and allowed to equilibrate for 2 weeks. Seedlings of lettuce of the variety Eden were transplanted into the pots, and the treatments kept at 80% field capacity. The treatments were replicated four times in a completely randomized design. At physiological maturity, the lettuce was harvested, and fresh and dry matter yields were taken. The C and N contents and N uptake in the harvested plants were also determined. Results indicate that conditioning the soil with Bioplant at half and the manufacturer's recommended rates increased N uptake, resulting in higher carbon accumulation with concomitant increases in both fresh and dry matter yields. The results also show that amending the Rhodic Kandiustalf with Bioplant at twice the manufacturer's rate suppressed yield. Application of Bioplant at the manufacturer's recommended rate in combination with compost amended at 40 parts to 60 parts soil (v/v) saw a 47 and 90% respective significant yield increases in fresh weight and dry matter when only Bioplant was applied at the manufacturer's recommended rate. It is therefore recommended for Bioplant to be applied at the manufacturer's recommended rate of 825 mL/ha in combination with 40 parts of compost to 60 parts of soil (v/v).
Soils of Ghana, except for the few variants of Vertisols in the Accra plains, are generally low in fertility. Their organic carbon contents are <1%, and the levels of N and P are very low (SRID MoFA,
To obtain appreciable crop yields, the application of nutrient from external sources has become imperative. Application of inorganic fertilizers through the soil for plant uptake has been the commonest way by which nutrients are made available to crops in Ghana. Thus, there is application of mainly inorganic fertilizers, of which the ammonium-based ones (urea and sulfate of ammonia) are the most popular. Application of these fertilizers has also aggravated the acidity problem as a result of nitrification under aerobic conditions (Chang et al.,
Nutrient use efficiency of the already low rate of fertilizers applied to soils in Ghana is low because of the poor nutrient holding capacities of the soils as a result of the low organic matter content and the presence of the low-activity clays. Returns on fertilizer application are thus low, negatively affecting soil and crop productivity, and consequently food security. Improving nutrient use efficiency would demand increasing the organic matter content of soils in Ghana to improve on their nutrient holding capacity (Tandy et al.,
A drawback of the use of compost, especially, in short duration crops is the slow release of nutrients (Zhang et al.,
Bioplant is a soil conditioner manufactured by Artemis and Angel Company Limited in Bangkok, Thailand. Bioplant is a microbial liquid conditioner that contains bacteria and fungi and 7.00 g N/L, 4.00 g P2O5/L, and 5.10 g K2O/L among other nutrients. It is purported to stimulate the activity of beneficial microbes in soil to improve nutrient uptake and hence increase crop yield. For Bioplant to be very effective, the soil must have high content of organic matter which would boost the proliferation of beneficial microbes and hence improve nutrient release
Most soils in sub-Saharan Africa and particularly Ghana are low in organic carbon contents with levels lower than 10 g/kg (Jones et al.,
As a soil conditioner, Bioplant would be deemed efficacious if it aids in the release of nutrients rapidly to meet the demand of crops. This attribute could be evaluated best if Bioplant is assessed on short-duration crops. It is in the light of this that a screen house experiment was conducted using lettuce (
A screen house experiment was conducted using Bioplant as a booster for N availability in a compost-amended Toje Series with the hypothesis that the biofertilizer would enhance N availability and uptake and, consequently, increase the yield of lettuce.
The objectives of the study were two-fold:
to verify if the manufacturer's recommended application rate of the conditioner is effective in increasing N uptake and hence yield of lettuce in a highly weathered Ghanaian Rhodic Kandiustalf of low fertility and
to ascertain the efficacy of Bioplant when applied in combination with compost on the yield of lettuce.
The Toje Series, a Rhodic Kandiustalf, was used as the soil for the study. This soil is widely cultivated in the Coastal Savanna Zone of Ghana but is inherently low in fertility. The plow layer of the soil was sampled from an area that had had no known history of fertilizer and any soil conditioner application. The soil was air-dried and passed through a 2-mm sieve to obtain the fine earth fraction for some physicochemical analyses. Undisturbed soil samples were taken for the determination of bulk density and water holding capacity (WHC). The particle size distribution of the fine earth fraction was determined using the Bouyoucos hydrometer method (Day,
Maize stubble was co-composted with groundnut husk biochar in the ratio of eight parts of the maize stubble to two parts of groundnut husk biochar on volume-to-volume basis.
An unprocessed Toje Series (unprocessed soil) was packed into 1.7-L plastic pots with drainage holes to attain the field bulk density of the soil. Subsequently, the soil was mixed with the compost in two soil-to-compost ratios of 20:80 (C80) and 60:40 (C40) on a volume basis and packed. To another pot, only soil was packed (C0), and this served as the control. Bioplant (BP) as a conditioner was applied to the potted soils at four rates of zero (BP0), half the manufacturer's rate (BP1), the manufacturer's recommended rate (825 mL/ha) (BP2), and twice the manufacturer's rate (BP3). All the soils were allowed to equilibrate for 2 weeks amidst watering to attain 80% WHC. While allowing the soils to equilibrate, lettuce seeds of the variety Eden were nursed. At the end of the 2 weeks, the seedlings were transplanted at two per pot. The moisture content of the media for growth (soil ± compost ± Bioplant) was maintained at 80% WHC to avoid leaching. These were replicated four times. Thus, with three compost application rates of 0, 40, and 80 and four Bioplant application rates and four replications arranged in a completely randomized design, there were a total of 48 experimental units.
At maturity, the lettuce was harvested, and the fresh weight determined. The lettuce was then dried in an oven at 65°C until a constant weight was attained and the dry matter content taken. The dried lettuce leaves were then milled, and the C and N contents determined on a TruMac C–N analyzer. The N uptake in the leaves per pot for each treatment was estimated by multiplying the leaf N content with the dry weight.
After harvest, the soils from the various pots were poured out into plastic bowls, homogenized, and subsampled for air-drying. These were then sieved to obtain the fine earth fraction and analyzed for pH, organic carbon, total N, and available P as described earlier.
The aforementioned measured parameters were subjected to analysis of variance (ANOVA) using Genstat 12th edition to establish, if any, significant treatment effects at
Some physical and chemical properties of the soil used for the study are presented in
Some physicochemical properties of Toje Series
74.4 | 19.4 | 6.2 | 1.3 | 5.7 | 0.35 | 8.0 | 0.7 | 5.96 | 5.62 |
Some chemical properties of the compost used in the study are presented in
Some chemical properties of the compost used.
pH (1:1)water | 7.4 |
EC (dS/m) | 4.67 |
Total carbon (g/kg) | 326.4 |
Total nitrogen (g/kg) | 13.2 |
Available nitrogen (g/kg) | 0.9 |
Total P (mg/kg) | 7,366.7 |
Available P (mg/kg) | 370.0 |
Total Ca (g/kg) | 6.05 |
Total Mg (g/kg) | 5.41 |
Total Na (g/kg) | 2.16 |
Total K (g/kg) | 50.03 |
The effect of compost on lettuce yield, nutrient content, and uptake is presented in
Effect of compost on yield, nutrient composition and N uptake in lettuce
C0 | 104.27a | 3.98a | 410.8a | 36.7ab | 0.15a |
C40 | 220.7b | 12.01b | 473.2c | 39.1b | 0.49b |
C80 | 107.3a | 3.58a | 432.8b | 34.9a | 0.13a |
Cv (%) | 18 | 17.8 | 4.5 | 8.8 | 18.5 |
Increasing the volume of compost applied to 80 parts decreased yield by almost 51% from 220.7 g in the C40 amended soil to 107.3 g fresh weight (
The carbon content of the lettuce in the un-amended soil was 410.8 g/kg. On application of 40 parts of the growing medium with compost (C40), the carbon content of the lettuce increased (
The effect of Bioplant on fresh and dry matter yields of lettuce is presented in
Effect of Bioplant on fresh and dry matter yields and N uptake of lettuce.
BP0 | 94.73a | 3.33a | 397.0a | 32.3a | 0.11a |
BP1 | 146.52b | 7.09c | 452.2b | 38.9b | 0.29c |
BP2 | 200.28c | 9.9d | 458.9b | 37.9b | 0.41d |
BP3 | 134.82b | 5.77b | 447.8b | 38.5b | 0.22b |
Cv (%) | 18 | 17.8 | 4.5 | 8.8 |
Increasing further the Bioplant application rate to that of the manufacturer recommendation (BP2) saw a 2.1-fold and almost 1.4-fold increases in fresh weight of lettuce over those grown in BP0 and BP1 soils, respectively.
Carbon accumulations were generally statistically similar (
Nitrogen levels in the lettuce followed a similar pattern as carbon, with the lettuce from the Bioplant-amended soils being similar in concentrations of the primary nutrient accumulated, albeit with significantly higher (
Increasing the application rate to twice the manufacturer's recommended rate (BP3) saw a 33% reduction in fresh matter yield from that of lettuce plants grown in soils conditioned with Bioplant at the manufacturer's recommended rate. Uptake of N consequently decreased to almost half that in lettuce at the recommended rate. Uptake of N in lettuce induced by Bioplant application was in the order (
The interactive effect of both compost and Bioplant application on yield of lettuce is presented in
Interactive effect of compost and Bioplant on yield, nutrient composition, and N uptake of lettuce.
C40 | No application | 172.53e | 6.59de | 430.6bc | 34.6abc | 0.23cd |
Half rate | 239.99f | 14.38f | 486.2de | 42.2cd | 0.61e | |
Full rate | 295.33f | 18.85g | 504.7e | 45.1cd | 0.85f | |
Double rate | 174.96e | 8.23e | 471.2.cde | 34.6abc | 0.28d | |
C80 | No application | 39.36a | 1.00a | 380.8a | 29.4a | 0.03a |
Half rate | 107.53bcd | 3.27abc | 436.7bc | 35.7abc | 0.12abc | |
Full rate | 156.74de | 5.79cde | 448.8bcd | 32.1ab | 0.19bcd | |
Double rate | 125.57bcde | 4.25bcd | 464.8cde | 42.4d | 0.18bcd | |
Cv (%) | 18 | 17.8 | 4.5 | 8.8 | 18.5 |
On doubling the rate of Bioplant to the full recommended rate while maintaining the compost rate at 40 parts (C40), the fresh weight of the lettuce did not increase significantly from that at the half rate of Bioplant. However, the dry matter yield increased almost by 31% from 14.38 to 18.85 g. Carbon and N accumulations were similar to those in lettuce when the half Bioplant rate and C40 compost were applied to the soil. Nitrogen uptake increased significantly (
At twice the manufacturer's recommended rate of Bioplant application in combination with C40, both fresh and dry matter yields of lettuce declined significantly from those at the manufacturer's rate, corroborating the decline in yield when twice the recommended rate was applied with no compost amendment. Combining Bioplant at the recommended rate with 40 parts of compost produced lettuce that is almost 95 g heavier in fresh weight and 9 g heavier in dry matter than the corresponding lettuce grown in only Bioplant-conditioned soil at the manufacturer's recommended rate (BP2). These increases represented 47 and 90% significant yield increases (
It is noteworthy that combining C40 and Bioplant at half the recommended rate produced lettuce with fresh weight that was statistically similar to the fresh weight obtained when C40 was combined with Bioplant at the manufacturer's recommended application rate. However, when the former (C40 + BP1) is compared with only Bioplant at half the manufacturer's recommended rate (BP1), there was a 64% increase in fresh weight of lettuce compared with the C40 + BP1-amended soil.
Combining 40 parts of the compost with all the three rates of Bioplant did not show any changes in C and N accumulation in the lettuce leaves, with the levels of carbon ranging between 471.2 and 504.7 g/kg and those of N between 35 and 45 g/kg. Nitrogen uptake among the treatments, however, was significantly different. Amendment of Bioplant and 40 parts of compost to the Toje Series saw N uptake in the following order: manufacturer's recommended rate > half the manufacturer's rate > double the manufacturer's rate (
When the compost was applied at 80 parts on a volume basis to 20 parts of the soil in combination with the three different rates of Bioplant, the yield of lettuce decreased with respect to those at similar rates of Bioplant and 40 parts compost amendment. At half the Bioplant recommended application rate with C40 compost amendment, fresh lettuce weight was 239.9 g, more than twice the weight when the same rate of Bioplant was amended with soils to which 80 parts of compost had been applied (
There was no difference in carbon contents of the leaves of lettuce among the three rates of Bioplant applied to 80 parts of compost-amended soil. However, doubling the manufacturer's recommended rate of Bioplant application reflected in the superior N accumulation to the other rates at 80 parts of compost amendment to the soil. This superior accumulation of N in lettuce grown in pots with double the manufacturer's recommended rate did not affect uptake of N as all the Bioplant treatments had statistically similar levels of N uptake under 80 parts of compost amended to the soil.
Some chemical properties of the residual soil after harvest are presented in
Effect of compost application on some residual soil properties
C0 | 5.8 | 0.37 | 7.8a | 0.528a | 3.20a |
C40 | 6.5 | 1.45 | 11.8b | 0.757b | 11.45b |
C80 | 7.1 | 2.34 | 14.5c | 0.905b | 18.10c |
The loamy sand texture of the soil coupled with the bulk density of 1.3 Mg/m3 gave a good indication of the soil's physical suitability for root growth and permeability, which are very important for the soil–plant–water relationship (McKenzie et al.,
The addition of compost to soil generally helps to improve the structure and fertility status of the soil. Additionally, amendment of the soil with the biochar-compost should increase the pH of the moderately acidic soils to near neutral to enhance P availability and dry matter yield (Latifah et al.,
As indicated in
The higher nitrogen uptake of lettuce in the BP1 and BP2 soils than their BP0 counterparts also reflected in their respective significantly superior carbon contents of about 450 g/kg relative to the 400 g/kg of BP0. A higher N uptake would promote better leaf expansion as a result of higher chlorophyll formation and hence higher assimilation of carbon (Gastal and Saugier,
A reduction in fresh matter yield following a 100% increase in the manufacturer's recommended Bioplant application rate to BP3 may have resulted in a lower N uptake, culminating in a lower dry matter yield of lettuce. It is evident that doubling the manufacturer's recommended application rate of Bioplant to the soil reduced the dry matter yield of lettuce significantly by 19 and 42% from the BP1- and BP2-conditioned soils, respectively. It thus appears that doubling the rate suppressed nutrient availability, leading to a decrease in leaf expansion and hence fresh and dry matter yields.
As indicated in
Results from the work have shown that Bioplant as a conditioner when applied to the Rhodic Kandiustalf at the manufacturer's recommended rate during land preparation boosts N uptake and increases yield of lettuce. For better and more efficient utilization of Bioplant, it is ideal to apply it in combination with some amount of compost.
It is recommended for Bioplant to be used in combination with compost or decomposed organic manure for better yield if the organic matter content of the soil is low. Under conditions of high organic matter contents of soils, Bioplant could be used without compost. Bioplant should be applied to the soil well-ahead of seeding or planting to boost microbial activity and mineralization to synchronize nutrient availability with uptake.
The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.
All authors listed have made substantial intellectual contributions to the work and approved it for publication.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
The authors would like to thank the Plant Protection and Regulatory Services Directorate of the Ministry of Food and Agriculture, Ghana, for the provision of the Bioplant conditioner.
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