Phosphorus (P) is an essential element for plant growth and development. Finding new P sources and ways to improve crop P utilization are necessary due to the depletion of phosphate reserves. Five crop species, buckwheat (Fagopyrum esculentum L.), maize (Zea mays L.), oilseed rape (Brassica napus L. ssp. oleifera (Moench) Metzg.), spelt wheat (Triticum spelta L.), and white lupine (Lupinus albus L.), were grown in pots containing sandy soil with chemical nutrients, digestate, and meat bone meal (MBM) without added nutrients. Thirty days after the seeding plants were harvested, the growth stage, soil-plant analysis development (SPAD) value, biomass, P content of the plants, colonization of the roots with endomycorrhiza, and soil pH were analyzed, and the number of fungal spores in the soil was counted. All species showed interaction with the P sources for measured traits, except for the rhizosphere pH. A high biomass was recorded in all species fertilized with various P sources compared to the unfertilized treatment. Buckwheat and spelt wheat showed a higher P uptake with MBM, and the mycorrhizal symbiosis improved with digestate or MBM compared to synthetic P. The results indicate that different species have adaptative mechanisms to various P sources which could improve the resilience and sustainability of cropping systems.

Essential oils (EOs) and Plant extracts (PEs) are gaining attention as eco-friendly alternatives to synthetic fungicides for the management of soil-borne fungi related to root rot and the wilt of marigolds. Here, EOs of Cinnamomum zeylanicum (cinnamon), Mentha piperita (peppermint), Syzygium aromaticum (clove), Thymus vulgaris (thyme), PEs of Cymbopogon citratus (lemongrass), Lantana camara (lantana), Ocimum basilicum (basil), and Zingiber officinales (ginger) were first evaluated in vitro for their inhibitory activity against the mycelium growth of the root rot and wilt fungi of marigold: Rhizoctonia solani, Sclerotinia sclerotiorum, Fusarium oxysporum, and F. solani, and in vivo for their activity in reducing disease progression. The results show that all EOs had a strong inhibitory activity on the mycelium growth of pathogens. Maximum inhibition of mycelium growth was achieved at a concentration of 1 mL/Lof S. aromaticum, C. zeylanicum, and M. piperita. The inhibition values were 100, 80.9, and 72.4% for F. solani, 100, 81.1, and 70% for S. sclerotiorum, 90.2, 79.4, and 69.1% for F. oxysporum, and 85.4, 78.2, and 68.7% for R. solani, respectively. Regarding plant extracts, the highest inhibition of mycelium growth was attained at a concentration of 20% of Z. officinales, C. citratus, and L. camara. The inhibition values were 77.4, 69.1, and 60.6% for F. solani, 76.5, 67.2, and 58% for S. sclerotiorum, 73.5, 68.2, and 56.3% for F. oxysporum, and 72, 64.8, and 55.2% for R. solani, respectively. In pot experiments, the application of EOs and PEs showed high efficiency in suppressing root rot and wilt of marigold at all concentrations used, especially at 3 mL/L for seed soaking (along with 1.5 mL/L for foliar spraying) for S. aromaticum, C. zeylanicum, and M. piperita EOs, and (40% for seed soaking along with 20% for foliar spraying) for Z. officinales, C. citratus, and L. camara PEs. All the treatments applied in the field greatly reduced the diseases in both seasons, especially S. aromaticum EO, C. zeylanicum EO, Z. officinales PE, and carbendazim treatments. This was accompanied by a significant improvement in morphological, yield, and phytochemical parameters of marigold as well as a significant increase in the activity of defense-related antioxidant enzymes. Overall, essential oils and plant extracts can be used effectively to control root rot and wilt in marigold as sustainable and eco-friendly botanical biofungicides.

Cassava has high energy value and rich nutritional content, yet its productivity in the tropics is seriously constrained by abiotic stresses such as water deficit and low potassium (K) nutrition. Systems that allow evaluation of genotypes in the field and greenhouse for nondestructive estimation of plant performance would be useful means for monitoring the health of plants for crop-management decisions. We investigated whether the red–green–blue (RGB) and multispectral images could be used to detect the previsual effects of water deficit and low K in cassava, and whether the crop quality changes due to low moisture and low K could be observed from the images. Pot experiments were conducted with cassava cuttings. The experimental design was a split-plot arranged in a completely randomized design. Treatments were three irrigation doses split into various K rates. Plant images were captured beginning 30 days after planting (DAP) and ended at 90 DAP when plants were harvested. Results show that biomass, chlorophyll, and net photosynthesis were estimated with the highest accuracy (R² = 0.90), followed by leaf area (R² = 0.76). Starch, energy, carotenoid, and cyanide were also estimated satisfactorily (R² > 0.80), although cyanide showed negative regression coefficients. All mineral elements showed lower estimation accuracy (R² = 0.14–0.48) and exhibited weak associations with the spectral indices. Use of the normalized difference vegetation index (NDVI), green area (GA), and simple ratio (SR) indices allowed better estimation of growth and key nutritional traits. Irrigation dose 30% of pot capacity enriched with 0.01 mM K reduced most index values but increased the crop senescence index (CSI). Increasing K to 16 mM over the irrigation doses resulted in high index values, but low CSI. The findings indicate that RGB and multispectral imaging can provide indirect measurements of growth and key nutritional traits in cassava. Hence, they can be used as a tool in various breeding programs to facilitate cultivar evaluation and support management decisions to avert stress, such as the decision to irrigate or apply fertilizers.

Leafy vegetables like lettuce (Lactuca sativa L.) naturally have high nitrate content and the European Commission has set maximum level for nitrate in lettuce. Glycinebetaine is an organic osmolyte alleviating plant stress, but its role in leaf nitrate accumulation remains unknown. The uptake of glycinebetaine by lettuce roots, and its potential to regulate lettuce nitrate content and improve plant quality were investigated. Two hydroponic lettuce experiments were conducted with different glycinebetaine application rates (Exp1: 0, 1, 7.5, and 15 mM; Exp2: 0, 1 + 1 + 1, 1 + 10, and 4 mM). Plants were analyzed at varying time points. Root application resulted in glycinebetaine uptake and translocation to the leaves. Glycinebetaine concentrations > 7.5 mM reduced leaf nitrate up to 40% and increased leaf dry matter content. Glycinebetaine showed a positive effect on leaf mineral and amino acid composition. Thus, glycinebetaine could be a novel strategy to reduce the nitrate content in hydroponic lettuce.

Most arid and semiarid areas are bare and greatly infested with intrusive wild species. Buffel grass (Cenchrus ciliaris L.) and Sudan grass (Sorghum sudanense Piper.) are the supreme drought-tolerant grasses that are commonly grown in dry regions. Besides water, nitrogen (N) is a vital element limiting the growth, yield, and herbage quality of such grasses since it has key roles in physiological and biochemical functions in plants. Hence, this study aimed at assessing the performance of Buffel and Sudan grasses under nitrogen fertilization in Mandera County. This study comprised a field trial laid as a split plot in a randomized complete block design with grasses being assigned to the main plots, whereas N rates (0, 35, 70, 105, and 140 kg N ha⁻¹) occupied the subplots. Data were collected on growth parameters (plant height, leaf length, number of leaves per plant, leaf width, stem girth, and tiller number), yield parameters (shoot weight, root weight, and aboveground biomass yield—DBY), and quality attributes (acid detergent fiber—ADF, crude protein—CP, and neutral detergent fiber—NDF). Across the seasons, plant height progressively increased with increasing N rates up to a maximum of 141 and 246 cm for Buffel grass and Sudan grass, respectively, which were associated with a 105 kg N ha⁻¹ rate. Nonetheless, there was no noteworthy enhancement in plant height (142 and 246 cm) with an additional upsurge in N fertilizer rate to 140 kg N ha⁻¹ relative to the one of 105 kg N ha⁻¹. Regarding the leaf length, Sudan grass had longer and wider leaves at all treatment levels than the Buffel grass. Plant height, leaf length, width, and the number of leaves per plant increased with increasing N level up to the rate of 140 kg N ha⁻¹, though this was not statistically different from the rate of 105 kg N ha⁻¹ for both kinds of grass. The results revealed that Sudan grass contained higher crude protein than Buffel grass at all levels of treatments (10.33 and 8.80% at the rate of 105 kg N ha⁻¹, respectively). More so, crude protein content was found to be higher in plots where N application was performed than in the control plots. There were great associations between the dependent variables (DBY, ADF, NDF, and CP) and independent variables (plant height, leaf length, No. of leaves, leaf width, stem girth, and No. of tillers), with the coefficient of regression ranging from 0.56 to 0.96 for Buffel grass and 0.59 to 0.96 for Sudan grass. Findings from this study indicate that for optimal growth, yield, and nutrient content benefits, Buffel and Sudan grasses ought to be grown using nitrogen fertilizer at a 105 kg N ha⁻¹ rate.

Cassava (Manihot esculenta Crantz) experiences intermittent water deficit and suffers from potassium (K) deficiency that seriously constrains its yield in the tropics. Currently, the interaction effect between deficit irrigation and K fertigation on growth and yield of cassava is unknown, especially during the early growth phase. Therefore, pot experiments were conducted under controlled greenhouse conditions using cassava cuttings. Treatments initiated at 30 days after planting included three irrigation doses (30%, 60%, 100% pot capacity) and five K (0.01, 1, 4, 16, and 32 mM) concentrations. The plants were harvested 90 days after planting. Decreasing irrigation dose to 30% together with 16 mM K lowered the leaf water potential by 69%, leaf osmotic potential by 41%, photosynthesis by 35%, stomatal conductance by 41%, water usage by 50%, leaf area by 17%, and whole-plant dry mass by 41%, compared with full-irrigated plants. Lowering the K concentration below 16 mM reduced the values further. Notably, growth and yield were decreased the least compared with optimal, when irrigation dose was decreased to 60% together with 16 mM K. The results demonstrate that deficit irrigation strategies could be utilized to develop management practices to improve cassava productivity by means of K fertigation under low moisture conditions.