Salinity may strongly influence the interaction between plant roots and surrounding soil, but this has been poorly studied for sodium sulfate (Na₂SO₄). The aim of this study was to investigate the effect of sodium chloride (NaCl) and Na₂SO₄ salinities on the soil chemical properties as well as rice physiological- and yield-related parameters of two contrasted cultivars (V14 (salt-sensitive) and Pokkali (salt-resistant)). Pot experiments were conducted using soil and electrolyte solutions, namely NaCl and Na₂SO₄, inducing two electrical conductivity levels (EC: 5 or 10 dS m⁻¹) of the soil solutions. The control treatment was water with salt-free tap water. Our results showed that soil pH increased under Na₂SO₄ salinity, while soil EC increased as the level of saline stress increased. Salinity induced an increase in Na⁺ concentrations on solid soil complex and in soil solution. NaCl reduced the stomatal density in salt-sensitive cultivar. The total protein contents in rice grain were higher in V14 than in Pokkali cultivar. Saline stress significantly affected all yield-related parameters and NaCl was more toxic than Na₂SO₄ for most of the studied parameters. Pokkali exhibited a higher tolerance to saline stress than V14, whatever the considered type of salt. It is concluded that different types of salts differently influence soil properties and plant responses and that those differences partly depend on the salt-resistance level of the considered cultivar.

To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yield components in rice, plants of Oryza sativa (cv. I Kong Pao (salt-sensitive)) were exposed in nutrient solutions to 20 mM Na₂SO₄ or 40 mM NaCl (electrical conductivity of c.a. 4.30 dS m⁻¹ for both solutions) from seedlings to maturity stage. Both types of salt induced a strong decrease in net photosynthesis (A_N) at the seedling and tillering stages, while the intercellular CO₂ concentrations (Ci) remained unaffected. Instantaneous transpiration (E) and stomatal conductance (g_s) decreased at the tillering and seedling stages, respectively, only in plants exposed to NaCl. Chloride salinity also strongly decreased photosynthetic pigments, while no impact was detected in response to Na₂SO₄. All yield-related parameters were affected by salinities, but NaCl was significantly more deleterious than Na₂SO₄ for the mean number of tillers produced per plant, spikelets sterility and non-viable pollen percentage. In contrast, both types of salinity similarly impacted the percentage of fertile tillers and 1000-grain weight. At the grain level, more than 90% of toxic ions (Na⁺, excess of Cl⁻ and S⁶⁺) accumulated in the hulls, thus preserving the internal part of the caryopses from toxic ion injuries.

Many growers rely on good agricultural extension services to successfully grow their crops. Correct field diagnoses of plant health problems are an essential starting point. However, some agricultural extension workers may have had limited capacity building in field diagnosis during their agricultural education, and many may have had limited or no continuing education possibilities during their advisory work life. As a result, errors may occur in the course of diagnosis of plant health problems with devastating consequences. The objective of this study, therefore, was to assess the value of short and inexpensive in-service training that is intended to improve the quality of field diagnosis of plant health problems. Eight groups of agricultural extension workers totaling 165 participants were trained during a 3-day-long intensive course in the diagnosis of plant health problems as part of the plant doctor training in the Plantwise program in Burundi (44 ± 9 years of age, 14 ± 10 years of experience in agriculture and 8 ± 7 years in extension; 10% females). Empirical data from before-versus-end and after-course analyses revealed that such courses can indeed increase knowledge and skills in field diagnosis by 20 ± 8% points during the training and by 9 ± 4% points when having worked for 8 to 19 months after training. The level of variability among extension workers was also reduced by 0.8 ± 1% points pre-course versus end-course, and by 1.1 ± 0.3% points from pre- versus post-course. Interestingly, there seemed little to no influence of work experience in agricultural extension on the quality of field diagnosis of plant health problems. More advanced educational levels only slightly improved the diagnosis quality of extension workers; gender played no role; younger workers performed slightly better than older ones. This may indicate a lack of opportunities for further training as part of continuing adult education. Our results suggest regularly repeated in-service training for agricultural practitioners may be beneficial. Investments in such training seem worthwhile since better diagnoses can lead to more appropriate pest management advice and judicious use of pesticides.

In field conditions, soil salinity may be due to an excess of different soluble salts. In order to compare the impact of chloride and sulfate salinities on rice, two contrasted cultivars (IKP: salt-sensitive and Pokkali: salt-resistant) were exposed to iso-strength Na⁺ nutrient solutions (NaCl 50 mM or Na₂SO₄ 25 mM; EC: 5.31 dS m⁻¹) for 2 weeks under controlled environmental conditions. It was found that NaCl was more toxic than Na₂SO₄, especially for the salt-sensitive IKP. Sodium and proline accumulation were higher while shoot osmotic potential was lower in NaCl-treated plants than in those exposed to Na₂SO₄. Chloride-treated plants exhibited a higher shoot malondialdehyde concentration, suggesting a higher level of lipid peroxidation while Na₂SO₄-treated plants presented a slightly higher total antioxidant activity. Pokkali was more tolerant than IKP to both types of toxicities although it accumulated similar concentration of toxic ions. Pokkali was able to reduce the root osmotic potential and to quickly recycle oxidized glutathione to reduced glutathione, which may help the plant to more efficiently control its oxidative status in stress conditions. It is concluded that different salts may have distinct impacts on the plant physiology and that differences may vary according to the considered cultivar.

Purpose: The use of composts in agriculture has many advantages on soil properties and the productivity of cultivated plants. This study aims to evaluate the response of the bean crop to organic fertilization consisting of composts from Lantana camara Linn, Calliandra Calothyrsus Meisn, and cow manure in combination or not with chemical fertilizers.Research Method: The experiment was carried out in a randomized complete block design on a very acidic ferralsol of Matongo commune in the northern part of Burundi. Each experimental plot corresponded to an application of a specific compost or cow manure combined or not with chemical fertilizers (dose N-P2O5-K2O: 18-46-30).Findings: Adding chemical fertilizers to cow manure and Lantana compost significantly increased the number of leaves, flowers, pods, and seeds, the total biomass, and the weight of seeds. These two treatments recorded the highest grain yields (1067 kg.ha-1 and 999 kg.ha-1 respectively). They were followed by the application of cow manure alone (582.90 kg.ha-1). The lowest yields were observed when applying Calliandra alone (167 kg.ha-1) or combined with chemical fertilizers (371 kg.ha-1), Lantana alone (338.15 kg.ha-1), chemical fertilizers alone (100.79 kg.ha-1), and on unfertilized soil (0.67 kg.ha-1).Originality/ Value: The Lantana camara compost can effectively replace farmyard manure for bean production on an acidic ferrallitic soil, and thus be useful to livestock-less farmers.