One of the biggest challenges in the intercropping system of two crops is to obtain the optimal dose of green manure and the adequate population density of the crops. So, the objective of this work was to evaluate the performance of beet and arugula intercropping, influenced by green manuring with Merremia aegyptia and Calotropis procera and arugula population densities in two cultivation years, in semi-arid environment. The experimental design used was in randomized complete blocks, with the treatments arranged in a 4 x 4 factorial scheme, with 4 repetitions. The first factor of this scheme consisted of equitable amounts of M. aegyptia and C. procera biomass (20, 35, 50 and 65 t ha-1 on a dry basis) and the second factor, by arugula population densities (40, 60, 80 and 100% of the recommended density for single cropping, corresponding to 400, 600, 800 and 1,000 thousand arugula plants ha-1). The production and its components were evaluated on beet and arugula. In addition to these characteristics, the following agro-economic indicators were also determined for each treatment: system productivity index (SPI), land equivalent coefficient (LEC) and monetary equivalent ratio (MER). The greatest agro-economic advantages of the beet with arugula intercropping were achieved with a system productivity index (SPI) of 53.47 t ha-1, land equivalent coefficient (LEC) of 0.84 and a monetary equivalent ratio (MER) of 1.56, respectively, combining 65 t ha-1 of M. aegyptia and C. procera biomass with the arugula population density of 1,000 thousand plants ha-1. The maximum optimized commercial productivity of beetroots in the system intercropped with arugula was 23.20 t ha-1 using 65 t ha-1 of M. aegyptia and C. procera and in the arugula population density of 1,000 thousand plants ha-1, while the maximum arugula productivity intercropped with beet was 9.65 t ha-1, in the same combination of green manures amount and arugula population density.

The use of a cropping system that provides producers with better land use, higher productivity per unit area, greater diversification in production, and consequently agro-economic advantages, has been the choice of vegetables producers. Therefore, the objective of this work was to evaluate the productive and agro-economic benefits of beet-lettuce intercropping under different equitable amounts of Merremia aegyptia and Calotropis procera biomass (20, 35, 50 and 65 t ha^-1 on a dry basis) in different lettuce population densities (150, 200, 250, and 300 thousand plants ha^-1), in two cropping years in semi-arid environment. In the cultures and in the intercropping, the production and its components and the agro-economic indexes were evaluated. The maximum production of beet commercial roots in intercropping with lettuce was obtained with a productivity of 33.77 t ha^-1 in the amount of 65 t ha^-1 of M. aegyptia and C. procera biomass incorporated into the soil and in the lettuce population density of 300 thousand plants per hectare, while the maximum lettuce leaf production was achieved with a productivity of 24.40 t ha^-1 in the same combination of green manure amounts and lettuce population densities. The greatest agro-economic advantages of the beet intercropping with lettuce were achieved with a system productivity index (SPI) of 32.97 t ha^-1, land equivalent coefficient (LEC) of 0.87 and a monetary equivalence ratio (MER) of 1.55, respectively, in the combination of 65 t ha^-1 of M. aegyptia and C. procera biomass with a lettuce population density of 300 thousand plants per hectare.

Producers who practice intercropped systems of leafy vegetables with tuberous ones, generally seek for systems that provide high productivity, greater diversification of production, high quality products and mainly agroeconomic return. Therefore, the objective of this work was to assess whether there is agro-economic viability of lettuce bi-cropping in intercrop with beet, under different equitable amounts of Merremia aegyptia and Calotropis procera biomass (20, 35, 50 and 65 t ha-1 on dry basis) and population densities of lettuce (150, 200, 250 and 300 thousand plants of lettuce ha-1), combined with 500 thousand plants per hectare of beet in two years of cultivation in semi-arid environment. Productivity of lettuce leaves and commercial productivity of beet roots were evaluated, as well as the agronomic indices: land equivalent ratio (LER), area-time equivalent ratio (ATER), productive efficiency index (PEI), score of the canonical variable (Z), actual yield loss (AYL), and the economic indicators: gross income (GI), net income (NI), monetary advantage (MA) and rate of return (RR). The highest agro-economic returns of the lettuce-beet intercropping were achieved with LER and ATER of 2.59 and 1.39; PEI and Z of 0.97 and 2.32; and AYL of 10.66; and GI, NI and MA of 94,742.89; 59,121.45; 56,631.98 R$ ha-1 and RR of R$ 2.75 for each real invested, respectively, in the combination of 65 t ha-1 of M. aegyptia and C. procera biomass and lettuce population density 300 thousand plants per hectare. Beet was the dominant crop and lettuce the dominated one. The lettuce and beet intercropping is highly viable when properly manured with biomass of M. aegyptia and C. procera, as they express agronomic and economic viability and sustainability in semi-arid environment.

One of the biggest challenges in intercropping of two or more crops is to maintain their productivity as that of their sole counterparts. In order to obtain sustainable intercropping systems in a semi-arid environment, this study evaluated the agro-economic advantage and sustainability of intercropped systems of carrot and cowpea, optimizing the green manuring and spatial arrangements. Experiments were conducted in the period from July to October 2017 and 2018, using a randomized complete block design with the treatments arranged in a 4 x 3 factorial scheme, with four replications. Treatments included four amounts of M. aegyptia incorporated into the soil (20, 35, 50, and 65 t ha-1 on dry basis) with three spatial arrangements (2:2, 3:3, and 4:4) between the components cultures formed from cowpea rows alternated with carrot rows. The agro-economic advantage indices evaluated in the intercropping systems were: land equivalent ratio (LER), area-time equivalent ratio (ATER), score of the canonical variable (Z), actual yield loss (AYL), intercropping advantage (IA), gross income (GI), net income (NI), rate of return (RR), and profit margin (PM). The highest agro-economic advantages of the carrot and cowpea intercropping were obtained for LER, ATER, NI, and RR of 2.60, 4.16, US$ 8,720.99 ha-1, and US$ 2.21, respectively, for M. aegyptia biomass amounts of 46.42, 47.82, 32.60 and 31.51t ha-1 added to the soil. The 2: 2 spatial arrangement was the one with the best productive performance, with higher net income and rate of return in the intercropping of carrot-cowpea.

Producing seeds in the organic production system still requires a lot of information regarding the fertilization and nutritional requirements. Thus, the objective of this study was to determine the dry mass and macronutrient accumulation curve in lettuce for seed production, aiming at cultivation in an organic system. The treatments consisted of two phosphorus doses (320 and 800 kg ha⁻¹ of P₂O₅, Yoorin^® thermophosphate source). The crisp lettuce plants, cultivar Solaris, were collected at eight stages (0, 14, 28, 42, 56, 70, 84, and 98 days after transplanting—DAT) for an analysis of the proposed characteristics. A nonlinear sigmoid regression curve was fitted and the results demonstrated continuous plant growth, accompanied by a gradual increase in dry matter throughout the experimental period, regardless of the phosphorus dose studied. The vegetative part of the lettuce plant shows slow initial growth, followed by acceleration up to the beginning of flowering (70 DAT), and stabilization after this period. The reproductive part of the lettuce plant begins to grow from 56 DAT, increasing the daily nutrient demand until the end of the seed maturation and harvest at 98 DAT. The dose of 800 kg ha⁻¹ of P₂O₅, the lettuce plant accumulated 1527.7, 308.2, 2922.6, 1658.4, 416.0, and 197.6 mg per plant of N, P, K, Ca, Mg, and S, respectively. The dose of 320 kg ha⁻¹ of P₂O₅, the lettuce plant accumulated 1743.1, 256.9, 2575.7, 1210.2, 358.8, and 185.5 mg per plant of N, P, K, Ca, Mg, and S, respectively. The greatest demand for nutrients in the plant occurred between 55 and 88 DAT.