Is dry soil planting an adaptation strategy for maize cultivation in semi-arid Tanzania?

The influence of climatic and environmental variables on sunflower planting season suitability in Tanzania

Crop survival and growth requires identification of correlations between appropriate suitable planting season and relevant climatic and environmental characteristics. Climatic and environmental conditions may cause water and heat stress at critical stages of crop development and thus affecting planting suitability. Consequently, this may affect crop yield and productivity. This study assesses the influence of climate and environmental variables on rain-fed sunflower planting season suitability in Tanzania. Data on rainfall, temperature, slope, elevation, soil and land use/or cover were accessed from publicly available sources using Google Earth Engine. This is a cloud-based geospatial computing platform for remote sensed datasets. Tanzania sunflower production calendar of 2022 was adopted to mark the start and end limits of planting across the country. The default climate and environmental parameters from FAO database were used. In addition, Pearson correlation was used to evaluate the relationship between rainfall, temperature over Normalized Difference Vegetation Index (NDVI) from 2000 to 2020 at five-year interval for January-April and June-September, for high and poor suitability season. The results showed that planting suitability of sunflower in Tanzania is driven more by rainfall than temperature. It was revealed that intra-annual planting suitability increases gradually from short to long- rain season and diminishes towards dry season of the year. January-April planting season window showing highest suitability (41.65%), whereas June-September indicating lowest suitability (0.05%). Though, not statistically significant, rainfall and NDVI were positively correlated with r = 0.65 and 0.75 whereas negative correlation existed between temperature and NDVI with r = -- 0.6 and - 0.77. We recommend sunflower subsector interventions that consider appropriate intra-regional and seasonal diversity as an important adaptive mechanism to ensure high sunflower yields.

Impacts of Long- and Short-Term of Irrigation with Treated Wastewater and Synthetic Fertilizers on the Growth, Biomass, Heavy Metal Content, and Energy Traits of Three Potential Bioenergy Crops in Arid Regions

The availability of suitable water is an important factor for increasing the cultivated areas and sustainability in arid (i.e., less than 200 mm precipitation per year) and semiarid regions (i.e., 200–700 mm precipitation per year). Therefore, this study aimed to analyze the impact of treated wastewater (TWW) and groundwater (GW) as well as synthetic fertilizers (50% and 100% of the recommended NPK dose; 150–150–60 kg N–P2O5–K2O ha−1) on the growth, biomass, energy traits, and macro and trace elements of maize (Zea mays L.), sorghum (Sorghum bicolor L.), and pearl millet (Pennisetum glaucum L) grown in old cultivated (first location; L1) and virgin soil (L2 and L3) as potential bioenergy crops. The soil in L1 has been irrigated with treated wastewater for the last 15 years and continued to be irrigated with treated wastewater in this investigation. The virgin soil was divided into two parts: the first part was irrigated with TWW, and the second part was irrigated with GW. The experiments were laid out in a split-plot with a randomized complete block design with water treatments (TWW in old and virgin soil, and GW in virgin soil) in main plots, and the two treatments of fertilization (50% and 100% of the recommended NPK dose) were distributed randomly in subplots. Compared with the crops irrigated with GW, the crops irrigated with TWW, whether grown on old or virgin soil, showed higher plant height, total chlorophyll content, leaf area per plant, total biomass, energy content, and gross energy with low ash. They also contained higher (but lower than permissible limits) concentrations of macro-elements (NPK) and trace elements (Fe, Mn, Cu, Zn, Cd, Pb, Ni, and Co). In addition, the application of a 50% recommended dose of NPK with TWW showed equivalent results to a 100% recommended dose of NPK on all measured parameters with few exceptions. In conclusion, the TWW can be used to irrigate field crops allocated for bioenergy production in arid regions because it does not harm the plants and environment. In addition, the 50% recommended dose of NPK fertilizer exerted no negative effects on the growth and energy production of field crops, thereby protecting the environment and reducing the leaching of excessive fertilizers into GW.

Thermal Stresses in Maize: Effects and Management Strategies

Climate change can decrease the global maize productivity and grain quality. Maize crop requires an optimal temperature for better harvest productivity. A suboptimal temperature at any critical stage for a prolonged duration can negatively affect the growth and yield formation processes. This review discusses the negative impact of temperature extremes (high and low temperatures) on the morpho-physiological, biochemical, and nutritional traits of the maize crop. High temperature stress limits pollen viability and silks receptivity, leading to a significant reduction in seed setting and grain yield. Likewise, severe alterations in growth rate, photosynthesis, dry matter accumulation, cellular membranes, and antioxidant enzyme activities under low temperature collectively limit maize productivity. We also discussed various strategies with practical examples to cope with temperature stresses, including cultural practices, exogenous protectants, breeding climate-smart crops, and molecular genomics approaches. We reviewed that identified quantitative trait loci (QTLs) and genes controlling high- and low temperature stress tolerance in maize could be introgressed into otherwise elite cultivars to develop stress-tolerant cultivars. Genome editing has become a key tool for developing climate-resilient crops. Moreover, challenges to maize crop improvement such as lack of adequate resources for breeding in poor countries, poor communication among the scientists of developing and developed countries, problems in germplasm exchange, and high cost of advanced high-throughput phenotyping systems are discussed. In the end, future perspectives for maize improvement are discussed, which briefly include new breeding technologies such as transgene-free clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas)-mediated genome editing for thermo-stress tolerance in maize.

Impacts of Agroclimatic Variability on Maize Production in the Setsoto Municipality in the Free State Province, South Africa

The majority of people in South Africa eat maize, which is grown as a rain-fed crop in the summer rainfall areas of the country, as their staple food. The country is usually food secure except in drought years, which are expected to increase in severity and frequency. This study investigated the impacts of rainfall and minimum and maximum temperatures on maize yield in the Setsoto municipality of the Free State province of South Africa from 1985 to 2016. The variation of the agroclimatic variables, including the Palmer stress diversity index (PSDI), was investigated over the growing period (Oct–Apr) which varied across the four target stations (Clocolan, Senekal, Marquard and Ficksburg). The highest coefficients of variance (CV) recorded for the minimum and maximum temperatures and rainfall were 16.2%, 6.2% and 29% during the growing period. Non-parametric Mann Kendal and Sen’s slope estimator were used for the trend analysis. The result showed significant positive trends in minimum temperature across the stations except for Clocolan where a negative trend of 0.2 to 0.12 °C year−1 was observed. The maximum temperature increased significantly across all the stations by 0.04–0.05 °C year−1 during the growing period. The temperature effects were most noticeable in the months of November and February when leaf initiation and kernel filling occur, respectively. The changes in rainfall were significant only in Ficksburg in the month of January with a value of 2.34 mm year−1. Nevertheless, the rainfall showed a strong positive correlation with yield (r 0.46, p = < 0.05). The overall variation in maize production is explained by the contribution of the agroclimatic parameters; the minimum temperature (R2 0.13–0.152), maximum temperature (R2 0.214–0.432) and rainfall (R2 0.17–0.473) for the growing period across the stations during the study period. The PSDI showed dry years and wet years but with most of the years recording close to normal rainfall. An increase in both the minimum and maximum temperatures over time will have a negative impact on crop yield.

Low Doses of Cuscuta reflexa Extract Act as Natural Biostimulants to Improve the Germination Vigor, Growth, and Grain Yield of Wheat Grown under Water Stress: Photosynthetic Pigments, Antioxidative Defense Mechanisms, and Nutrient Acquisition

The present study was conducted to investigate the effects of Cuscuta reflexa extract (CRE) on the activities of germination enzymes, seed germination vigor, biomass production, physio-biochemical attributes, and seed yield of water-stressed wheat plants. Different levels of CRE (0, 10, 20, 30, 40, and 50%), including water soaking, were used as seed priming. Water stress negatively affected the seed germination, germination enzyme activities, growth, yield, and different physio-biochemical attributes of wheat plants. Low doses of CRE (10, 20, and 30%) ameliorated the adverse effects of water stress on seed germination attributes, and activities of germination enzymes, but negative impacts were recorded at higher doses (40 and 50%) of CRE. Water-stressed wheat plants grown from seeds pre-treated with low doses of CRE also showed better growth and yield as compared with non-treated ones, and that was associated with an improvement in water relations, photosynthetic pigments, nutrient acquisition, reduced lipid peroxidation, and better antioxidative defense mechanisms. The maximum increase in seed yield was 14.77 and 12.32%, found in plants grown from seeds treated with 20% and 10% CRE, respectively. In conclusion, it is suggested that using low doses of CRE as seed priming can contribute to better wheat yield under water stress, especially in semi-arid and arid areas.

Modelling Rainfed Pearl Millet Yield Sensitivity to Abiotic Stresses in Semi-Arid Central Tanzania, Eastern Africa

Drought and heat-tolerant crops, such as Pearl millet (Pennisetum glaucum), are priority crops for fighting hunger in semi-arid regions. Assessing its performance under future climate scenarios is critical for determining its resilience and sustainability. Field experiments were conducted over two consecutive seasons (2015/2016 and 2016/2017) to determine the yield responses of the crop (pearl millet variety “Okoa”) to microdose fertilizer application in a semi-arid region of Tanzania. Data from the experiment were used to calibrate and validate the DSSAT model (CERES Millet). Subsequently, the model evaluated synthetic climate change scenarios for temperature increments and precipitation changes based on historic observations (2010–2018). Temperature increases of +0.5 to +3.0 °C (from baseline), under non-fertilized (NF) and fertilizer microdose (MD) conditions were used to evaluate nine planting dates of pearl millet from early (5 December) to late planting (25 February), based on increments of 10 days. The planting date with the highest yields was subjected to 49 synthetic scenarios of climate change for temperature increments and precipitation changes (of −30% up to +30% from baseline) to simulate yield responses. Results show that the model reproduced the phenology and yield, indicating a very good performance. Model simulations indicate that temperature increases negatively affected yields for all planting dates under NF and MD. Early and late planting windows were more negatively affected than the normal planting window, implying that temperature increases reduced the length of effective planting window for achieving high yields in both NF and MD. Farmers must adjust their planting timing, while the timely availability of seeds and fertilizer is critical. Precipitation increases had a positive effect on yields under all tested temperature increments, but Okoa cultivar only has steady yield increases up to a maximum of 1.5 °C, beyond which yields decline. This informs the need for further breeding or testing of other cultivars that are more heat tolerant. However, under MD, the temperature increments and precipitation change scenarios are higher than under NF, indicating a high potential of yield improvement under MD, especially with precipitation increases. Further investigation should focus on other cropping strategies such as the use of in-field rainwater harvesting and heat-tolerant cultivars to mitigate the effects of temperature increase and change in precipitation on pearl millet yield.

Analysis of Intra and Interseasonal Rainfall Variability and Its Effects on Pearl Millet Yield in a Semiarid Agroclimate: Significance of Scattered Fields and Tied Ridges

Establishing food security in sub-Saharan African countries requires a comprehensive and high resolution understanding of the driving factors of crop production. Poor soil and adverse climate conditions are among the major drivers of poor regional crop production. Drought and rainfall variability challenges are not fully being addressed by rainfed producers in semiarid areas. In this study, we analysed the spatiotemporal rainfall variability (STRV) and its effects on pearl millet yield using two seasons of data collected from 38 rain gauge stations scattered randomly in farm plots within a 1500 ha area of semiarid central Tanzania. The STRV effects on pearl millet yield under flat and tied ridge management were analysed. Our results show that seasonal rainfall can vary significantly for neighboring fields at distances of less than 200 m, which impacts yield. The STRV for daily rainfall was found to be more critical than for total seasonal rainfall amounts. Scattering fields can help farmers avoid total harvest loss by obtaining at least some yield from the areas that received adequate rain. The use of tied ridges is recommended to conserve soil moisture and improve yields more than flat cultivation in semiarid areas.