The citrus yield in Brazil is not ranked among the best in the world, potentially due to inadequate management by citrus growers. The low adoption of conservation agriculture (CA) techniques and the improper application of herbicides are also well-known problems. Thus, this study evaluated the use of CA techniques, and twoUrochloaspecies (ruzi grass and signal grass) were used as cover crops. Two different types of mowers (ecological, EM; conventional, CM) launched the mowed biomass into different positions within a young Tahiti acid lime orchard (up to four years old). In addition, the integration of glyphosate into this management system was evaluated, with (GLY) and without (NO GLY) glyphosate application. This experiment was conducted across three growing seasons (2011-2014), in Mogi Mirim, São Paulo State, Brazil. The cover crop biomass yields and the effects of the mowing treatments, weed density, vegetative growth and fruit yields of the Tahiti acid lime trees were evaluated. In terms of major results, signal grass produced higher biomass yield values (up to 64%) than ruzi grass; EM promoted higher mowed biomass values in the intra-row (up to 5.1 ton ha⁻¹, 9.0 times higher than CM), and a higher canopy volume (up to 33% than CM). These results were enhanced when ruzi grass was associated with the EM (56% lower weed density; 126% higher fruit yield than CM) and with GLY (52% higher fruit yield than NO GLY); and EM with GLY (43% lesser weed density and 107% higher fruit yield than NO GLY). Overall, ruzi grass was a good cover crop because it provided less competition for the citrus trees, EM provided a mulch layer in the intra-row of the citrus trees, and associated with GLY, these approaches could provide options for an integrated and more sustainable weed management, primarily for young Tahiti acid lime orchards.

The management of soil cover plants (intercropping) in orchards can contribute to increase productivity of citrus trees. Thus, the present research aimed to evaluate different planting systems for Tahiti acid lime grafted onto Flying Dragon trifoliate orange, a dwarfing rootstock, at high planting density (1,157 trees ha^–1). The study was set up in four tillage systems, using Urochloa ruziziensis as an intercrop species in the orchard, and conducted for 5 years: no-tillage (NT), no-tillage and no-herbicide (NT-NH), minimum tillage (MT) and conventional tillage (CT; without intercropping). Dry matter (DM) production of biomass in the row and interrow of the orchard was evaluated yearly, as well as weed density, soil physical and chemical characteristics, plant water and nutritional status, and fruit yield of trees. Greater deposition of DM of biomass was observed in the row of citrus planting for treatments NT and NT-NH compared to CT and MT treatments, which led to reduced undesirable weed populations. The NT treatment also provided increases of 79% in potassium (K) nutrient concentrations in the leaves of trees and 60% in exchangeable K in the soil surface layer, in the first 2 years evaluated. The maintenance of the Urochloa ruziziensis mulch in the NT system also provided higher soil volumetric moisture content and consequently lower soil resistance penetration and water stress on trees, evidenced by the predawn plant leaf water potential (<1 MPa). Moreover, the NT treatment provided an average increase of 56% of fruit yield from trees compared to the CT treatment during three harvests. This long-term study demonstrated the contribution of the no-tillage system using a favorable cover crop to increase the yield of Tahiti acid lime fruits and maintain the soil quality most required for the sustainability of citrus production.

The excessive use of glyphosate by Brazilian citrus growers leads to a vicious and unsustainable circle: Increasing the glyphosate use and the selection pressure of resistant/tolerant weeds, as well as the phytointoxication of the crop. In addition, there is speculation on the consequences of using glyphosate and the studies are not conclusive. Therefore, this study aimed to evaluate the glyphosate management in citrus orchards by assessing its effects in a 5-year field experiment using different doses and application frequencies. Here, we determine the weed control levels, the orchard growth and fruit yield, as well as the economic viability of the treatments. Higher weed control was observed more often with the increasing frequency of glyphosate application, and occasionally with increasing doses. However, some species predominated even at high glyphosate usage, such as BIDPI (Bidens pilosa (L.)), RAPRA (Raphanus raphanistrum (L.)), and ERICA (Conyza canadensis (L.) Cronquist). Phytotoxicity symptoms were demonstrated up to the fourth year of the orchard, and onwards the plants no longer expressed them. This was a highlight, since there was a decrease over time in growth (up to 5.3 m³) and fruit yield (up to 36.3 t ha⁻¹), with losses that reached −56% of the total income. This is the first report to demonstrate that the increase in glyphosate usage can occasionally increase weed control, but it can also decrease orchard development and its financial viability.

Mandarins occupy the third group among citrus produced in Brazil. Primarily aimed at the fresh fruit market, commercial orchards have suffered significant production losses due to the high incidence of diseases, such as the alternaria brown spot (ABS) and huanglongbing (HLB). The fact that 80% of the orchards are composed of two varieties, Ponkan mandarin and Murcott tangor, which are highly susceptible to both diseases, demands intensive chemical control of the diseases in the field, which has resulted in a significant increase in production costs and a negative environmental impact. A total of one hundred and seventy-three mandarin accessions, including several species and hybrids belonging to the Collections of the Instituto Agronômico de Campinas (IAC), were evaluated in the field in an endemic location for the diseases. Evaluations of the incidence and severity of the diseases showed a range of genotypes tolerant to ABS that could replace the current commercial varieties, mainly within the clementine and willow leaf mandarin groups. Although, with differences in incidence and susceptibility to HLB, there are no tolerant varieties to this disease, which significantly impacts the loss of fruit quality.

Techniques such as intercropping and minimum tillage improve soil quality, including soil microbial activity, which stimulates the efficient use of soil resources by plants. However, the effects of such practices in soil under citrus orchards have not been well characterized. In this study, we aimed to determine the effects of mowing and intercrop species on soil microbiological characteristics beneath a Tahiti acid lime orchard. The orchard was planted using minimum tillage and intercropped with two species of Urochloa species (U. ruziziensis—ruzi grass; U. decumbens—signal grass), with two types of mowers for Urochloa biomass (ecological; conventional) and herbicide applications. The study was conducted over 10 years. The ecological mower made the largest deposition of the intercrop biomass, thus providing the lowest disturbance of soil microbial activity and increasing, on average over all 10 years, the basal soil respiration (45%), microbial biomass carbon (25%), abundance of 16S rRNA (1.5%) and ITS (3.5%) genes, and arbuscular mycorrhizal fungi (30%), and providing a ca. 20% higher fruit yield. U. ruziziensis in combination with ecological mowing stimulated the abundance of the genes nifH (1.5%) and phoD (3.0%). The herbicide showed little influence. We conclude that the use of U. ruziziensis as an intercrop in citrus orchards subjected to ecological mowing can be recommended for improving and sustaining soil quality and citrus fruit production.