Effects of Cowpea-Amaranth Intercropping and Fertiliser Application on Soil Phosphatase Activities, Available Soil Phosphorus, and Crop Growth Response

The potential of durum wheat-chickpea intercropping to improve the soil available phosphorus status and biomass production in a subtropical climate

The intercropping system is a promising approach to augmenting the soil nutrient status and promoting sustainable crop production. However, it is not known whether intercropping improves the soil phosphorus (P) status in alluvial soils with low P under subtropical climates. Over two growing seasons--2019-2020 and 2020-2021--two experimental fields were employed to explore the effect of durum wheat (Dw) and chickpea (Cp) cropping systems on the soil available P. A randomized complete block design was used in this experiment, with three blocks each divided into three plots. Each plot was used for one of the following three treatments with three replications: Dw monocrop (Dw-MC), Cp monocrop (Cp-MC), and Dw + Cp intercrop (CpDw-InC), with bulk soil (BS) used as a control. A reduction in the rhizosphere soil pH (-0.44 and -0.11 unit) was observed in the (Cp-MC) and (CpDw-InC) treatments over BS, occurring concomitantly with a significant increase in available P in the rhizosphere soil of around 28.45% for CpDw-InC and 24.9% for Cp-MC over BS. Conversely, the rhizosphere soil pH was significantly higher (+0.12 units) in the Dw-MC treatments. In addition, intercropping enhanced the soil microbial biomass P, with strong positive correlations observed between the biomass P and available P in the Cp-MC treatment, whereas this correlation was negative in the CpDw-InC and Dw-MC treatments. These findings suggested that Cp intercropped with Dw could be a viable approach in enhancing the available P through improved pH variation and biomass P when cultivated on alluvial soil under a subtropical climate.

Alleviating summer heat stress in cowpea-baby corn intercropping with stress-reducing chemicals and fertility variations

Over the past century, the average surface temperature and recurrent heatwaves have been steadily rising, especially during the summer season, which is affecting the yield potential of most food crops. Hence, diversification in cropping systems with suitable fertilizer management is an urgent need to ensure high yield potential during the summer season. Since intercropping has emerged as an important strategy to increase food production, the present study comprises five intercropping systems in the main plot (sole cowpea, sole baby corn, cowpea + baby corn in 2:1, 3:1, and 4:1 row ratio), three levels of fertilizer viz. 100 (N20 P40), 125 (N25 P50), and 150% (N30 P60) recommended dose of fertilizer (RDF) in the subplot, along with two stress-mitigating chemicals (0.5% CaCl2 and 1% KNO3) in the sub-sub plots. A split-split plot system with four replications was established to carry out the field experiment. The effect of intercropping, fertilizer levels, and stress-mitigating chemicals on crop growth rate (CGR), relative growth rate (RGR), plant temperature, relative water content (RWC) and chlorophyll content of cowpea and baby corn, as well as cowpea equivalent yield (CEY), was investigated during the summer seasons of 2019 and 2020. The experiment was conducted at Agriculture University, Kota (Rajasthan), India. Results showed that CGR, RGR, RWC and chlorophyll content of both crops and CEY were maximum under intercropping of cowpea and baby corn in a 2:1 row ratio compared to other intercropping systems. However, the plant temperature of both crops was significantly lower under this system. CEY, CGR, RGR, and chlorophyll content were considerably greater in the subplots with a fertilizer application of 150% RDF compared to lower levels of fertilizer (100 and 125% RDF). Our findings further show that foliar application of CaCl2 0.5% at the flowering and pod-developing stages of cowpea dramatically boosted CEY, CGR, RGR, RWC, and chlorophyll content of both crops and lowered the plant temperature.

Effects of different planting distances and fertilizer use on the remediation of farmland contaminated with Cd by intercropping Cucurbita moschata and Amaranthus hypochondriacus L

Selecting suitable agronomic measures can strengthen the application of intercropping in the remediation of cadmium (Cd)-contaminated soil. In this study, the effects of different planting densities and fertilizer applications on the crop growth and Cd absorption of a pumpkin (Cucurbita moschata)-Amaranthus hypochondriacus L. intercropping system was determined. The goal was to provide enhanced means and a scientific basis for the promotion and application of this intercropping system. The Cd content of pumpkin in different planting systems was lower than the national food safety standard (0.05 mg kg^-1). In the IN-1 (4 pumpkin plants intercropped with 200 A. hypochondriacus plants) and IN-2 (4 pumpkin plants intercropped with 400 A. hypochondriacus plants) intercropping systems, the bioconcentration amount (BCA) per plant of Cd in A. hypochondriacus increased by 32.43% and 25.25%, respectively, compared with that of the monocropping system (P < 0.05). The IN-2 system had the highest equivalent ratio of heavy metal removal (3.08), indicating that this model had a substantial advantage for removing Cd. The land equivalent ratio of IN-1 (2.89) and IN-2 (2.60) was significantly higher than that of other intercropping systems, indicating that these two models had obvious yield advantages. In our study, chicken manure was the best at promoting the growth and yield of the two plants and sludge treatment significantly enhance Cd absorption of A. hypochondriacus. In general, intercropping four pumpkin plants with 400 A. hypochondriacus plants and applying chicken manure fertilizer can strengthen the application of this intercropping system in Cd-contaminated soil.

Could a Legume-Switchgrass Sod-Seeding System Increase Forage Productivity?

Nowadays, the lack of cattle feed, particularly green fodder, has become a key limiting factor in the agricultural economy. Switchgrass appears to offer a viable solution to the feed shortage. An improved cultivation practice might be needed to boost switchgrass forage production all season long. This study was conducted to quantify the positive effects of introducing different legume crops (vetch and pea), optimally fertilized, on the production and quality of mixed harvested switchgrass-legumes hay in late spring (May) and switchgrass hay harvested once more in early fall (September). The studied intercropping systems, independently of the legume species used, increased forage productivity (almost threefold), reaching 7.5 t ha^-1 and quality characteristics, with protein content almost rising threefold, reaching 12.5%. The aforementioned practice can assist the perennial crop (switchgrass) in providing a high hay production during the early fall harvest, even without fertilization. The overall annual economic benefit for the farmers may be increased by 90-720 € per ha, depending on the prevailing weather conditions. Overall, it may be concluded that the suggested cropping system produces a significantly higher yield of cattle feed compared to traditional monocultures, improving the agricultural economy while reducing the negative effects of modern agriculture on the environment.

Inoculating plant growth-promoting bacteria and arbuscular mycorrhiza fungi modulates rhizosphere acid phosphatase and nodulation activities and enhance the productivity of soybean (Glycine max)

Soybean [Glycine max (L.) Merrill] cultivation is important for its dual role as rich source of dietary protein and soil fertility enhancer, but production is constrained by soil nutrient deficiencies. This is often resolved using chemical fertilizers that exert deleterious effects on the environment when applied in excess. This field study was conducted at Nkolbisson-Yaoundé in the agro-ecological zone V of Cameroon to assess the performance of soybean when inoculated with plant growth-promoting bacteria (PGPB) and arbuscular mycorrhiza fungi (AMF), with or without NPK fertilizer addition. Ten treatments (Control, PGPB, AMF, PGPB+AMF, PGPB+N, PGPB+PK, PGPB+N+PK, PGPB+AMF+N, PGPB+AMF+PK, and PGPB+AMF+N+PK) were established in a randomized complete block design with three replicates. Mycorrhizal colonization was only observed in AMF-inoculated soybean roots. In comparison to control, sole inoculation of PGPB and AMF increased the number of root nodules by 67.2% and 57%, respectively. Co-application of PGPB and AMF increased the number of root nodules by 68.4%, while the addition of NPK fertilizers significantly increased the number of root nodules by 66.9-68.6% compared to control. Acid phosphatase activity in soybean rhizosphere ranged from 46.1 to 85.1 mg h^-1 kg^-1 and differed significantly across treatments (p < 0.001). When compared to control, PGPB or AMF or their co-inoculation, and the addition of NPK fertilizers increased the acid phosphatase activity by 45.8%, 27%, 37.6%, and 26.2-37.2%, respectively. Sole inoculation of PGPB or AMF and their integration with NPK fertilizer increased soybean yield and grain contents (e.g., carbohydrate, protein, zinc, and iron) compared to the control (p < 0.001). Soil phosphorus correlated significantly (p < 0.05) with soybean grain protein (r = 0.46) and carbohydrate (r = 0.41) contents. The effective root nodules correlated significantly (p < 0.001) with acid phosphatase (r = 0.67) and soybean yield (r = 0.66). Acid phosphatase correlated significantly (p < 0.001) with soybean grain yield (r = 0.63) and carbohydrate (r = 0.61) content. Effective root nodules correlated significantly with carbohydrate (r = 0.87, p < 0.001), protein (r = 0.46, p < 0.01), zinc (r = 0.59, p < 0.001), and iron (r = 0.77, p < 0.01) contents in soybean grains. Overall, these findings indicate strong relationships between farm management practices, microbial activities in the rhizosphere, and soybean performance.

Indicators for assessment of soil quality: a mini-review

Soil quality is the competence of soil to perform necessary functions that are able to maintain animal and plant productivity of the soil. Soil consists of various physical, chemical, and biological parameters, and all these parameters are involved in the critical functioning of soil. There is a need for continuous assessment of soil quality as soil is a complex and dynamic constituent of Earth's biosphere that is continuously changing by natural and anthropogenic disturbances. Any perturbations in the soil cause disturbances in the physical (soil texture, bulk density, etc.), chemical (pH, salinity, organic carbon, etc.), and biological (microbes and enzymes) parameters. These physical, chemical, and biological parameters can serve as indicators for soil quality assessment. However, soil quality assessment cannot be possible by evaluating only one parameter out of physical, chemical, or biological. So, there is an emergent need to establish a minimum dataset (MDS) which shall include physical, chemical, and biological parameters to assess the quality of the given soil. This review attempts to describe various physical, chemical, and biological parameters, combinations of which can be used in the establishment of MDS.