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The growing population of tropical countries has led to a new awareness of the importance of vegetables as a source of essential foods and nutrients. The success of vegetable cultivation depends to a large extent on high-quality seedlings. This work aimed at evaluating the effects of different substrates and different nutrient solution concentrations on the development of lettuce and Chinese cabbage seedlings in a semi-arid tropical area. Three independent experiments were conducted at the Soil and Water Research Station at Yezin Agriculture University, Myanmar (Myanmar, 19.83° N; 96.27° E). In all experiments a randomized block design was implemented with four treatments and three repetitions. In the first experiment the adaptability of lettuce seedling to two substrates (namely a Hulls Manure mix composed by 50% of mature cattle manure and 50% of carbonized rice husk and a soil based substrate constituted by 70% local soil, 20% burned rice husk, and 10% fresh cattle manure) and two nutrient solutions with different electrical conductivities (ECs) (W0.1, stored rainwater with EC = 0.13 dS m−1 and NS1.2, nutrient solution with EC = 1.20 dS m−1) were tested. In the second and third experiments, two species (lettuce and Chinese cabbage) were assessed for their response to nutrient solution concentrations. In both crops, 4 fertigation treatments (W0.1; NS0.6; NS1.2; and NS1.8) were supplied, by modulating the concentration of a compound mineral fertilizer (15:15:15) in the following ranges: W0.1: 0 g L−1, electrical conductivity (EC) 0.13 dS m−1, NS0.6: 0.3 g L−1, EC of 0.60 dS m−1; NS1.2: 0.6 g L−1, 1.2 dS m−1 EC, and NS1.8: 0.9 g L−1, 1.8 dS m−1 EC. Adopting different substrates and applying different nutrient solutions significantly affected growth (fresh weight and leaf morphology) and some physiological parameters (stomatal conductance, leaf temperature, and leaf chlorophyll content) of lettuce and Chinese cabbage seedling. From the first experiment, the combination of the soil based substrate and NS1.2 treatments allowed us to improve the seedlings’ growth. In the second experiment, highest growth of lettuce and Chinese cabbage seedlings was associated with NS1.2 and NS1.8, respectively. The presented results allow for the optimization of both growing media and nutrient solution management when lettuce and Chinese cabbage seedling are produced in the Central Dry Zone of Myanmar.

Simplified soilless cultivation (SSC) systems have globally spread as growing solutions for low fertility soil regions, low availability of water irrigation, small areas and polluted environments. In the present study, four independent experiments were conducted for assessing the applicability of SSC in the northeast of Brazil (NE-Brazil) and the central dry zone of Myanmar (CDZ-Myanmar). In the first two experiments, the potentiality for lettuce crop production and water use efficiency (WUE) in an SSC system compared to traditional on-soil cultivation was addressed. Then, the definition of how main crop features (cultivar, nutrient solution concentration, system orientation and crop position) within the SSC system affect productivity was evidenced. The adoption of SSC improved yield (+35% and +72%, in NE-Brazil and CDZ-Myanmar) and WUE (7.7 and 2.7 times higher, in NE-Brazil and CDZ-Myanmar) as compared to traditional on-soil cultivation. In NE-Brazil, an eastern orientation of the system enabled achievement of higher yield for some selected lettuce cultivars. Furthermore, in both the considered contexts, a lower concentration of the nutrient solution (1.2 vs. 1.8 dS m−1) and an upper plant position within the SSC system enabled achievement of higher yield and WUE. The experiments validate the applicability of SSC technologies for lettuce cultivation in tropical areas.

Water use efficiency is a main research target in agriculture, which consumes 70% of global freshwater. This study aimed at identifying sustainable water management strategies for the lettuce crop in a semi-arid climate. Three independent experiments were carried out on a commercial variety of lettuce (Lactuca sativa L.) by applying different irrigation levels based on crop evapotranspiration (ETc), estimated through both the Hargreaves–Samani and Penman–Monteith equations. In the first experiment, one treatment was also guided by soil moisture sensors. In the second and third experiments, a factorial combination was used, combining the different irrigation levels with two soil mulching treatments, namely soil without mulch, and soil mulched with dried rice straw residues. The application of different irrigation levels significantly affected plant growth, yield, and physiology. Both the adoption of sensors for guiding irrigation and the application of mulching with straw promoted higher yield. As the irrigation water level was reduced, the WUE (water use efficiency) increased. WUE was also increased by covering the soil with mulch. The experiments point out that accurate management of irrigation water using a drip irrigation system associated with soil mulching increases yield and improves the WUE of lettuce crops in the Central Dry Zone, Myanmar.

Rice (Oryza sativa L.) is an important target crop for water use reduction because of its greater input water requirement than other crops. The pot experiment was conducted to evaluate the effect of two different levels [full irrigation and deficit irrigation (50% Plant Available Moisture)] on the growth, yield, chlorophyll content and water use efficiency of improved rice lines. Preliminary test for drought tolerance for the one hundred improved rice lines was conducted and screened under pot experiments in the dry season of 2018. After screening this test, the selected rice lines were grown at two different water levels in the screen house during the rainy season of 2019. Each experiment was assigned as a randomized complete block design with three replications at Yezin Agricultural University. The result of the preliminary test in 2018 found that among the one hundred YAU improved rice lines, seven lines were tolerant to deficit irrigation. In 2019, all selected rice lines were also tolerant to deficit irrigation. These lines also produced the best performance of the plant growth, the grain yield and yield component characters when compared with the checked variety. However, deficit irrigation for all selected lines reduced these characters when compared with full irrigation. The five rice lines under deficit irrigation produced the high chlorophyll content and water use efficiency when compared with full irrigation. Thus, it can be concluded that the highest drought-tolerant rice lines would be useful for plant breeding program. [ABSTRACT FROM AUTHOR]

Soil salinity has become a serious threat to crop productivity worldwide. Salt tolerance for rice varieties vary with different stages against salinity. This study was to evaluate the effect of three different levels [0.2, 6.0, and 8.0 dS m-1] of salinity on the growth and yield of improved rice lines at different growth stages. This study was conducted as two-factor factorial in a randomized complete block design with three replications at Yezin Agricultural University in 2017 and 2018. After screening at seedling and vegetative stages, the selected rice lines were grown at three different salinity levels [3.3, 6.0, and 7.6 dS m-1] in the field. Among the one hundred improved rice lines, thirteen lines were tolerant to 8.0 dS m-1 during three weeks of application at seedling stage. Studies at vegetative stage showed that these thirteen lines were tolerant to 6.0 dS m-1 during six weeks of application. However, seven rice lines were moderately tolerant to 8.0 dS m-1 during six weeks of application in term of leaf mortality. In the field experiment, all seven rice lines were tolerant to 6.0 dS m-1 at all growth stages, whereas death occurred at 7.6 dS m-1. All agronomic parameters such as tiller numbers, panicle numbers and grain numbers per panicle were grown up to maturity under 6.0 dS m-1 at field condition. All these parameters were found to be major cause of yield reduction under saline conditions. [ABSTRACT FROM AUTHOR]