Strategies help crops produce in the face of water deficit

The strategies involve four lines: selection of cultivars tolerant to water stress; use of bioinputs; adoption of direct planting and Crop-Livestock Integration (ILP); and use of suboptimal irrigation

21.12.2021 | 13:10 (UTC -3)
Marina Torres Pessoa
Photo: Rosângela Maria Simeão
Photo: Rosângela Maria Simeão

Research from Embrapa Corn and Sorghum (MG) developed strategies that promote production stability in dryland crops of corn, sorghum, millet and pasture, which have suffered water deficits in recent years. The studies also include the efficient use of water in irrigated cultivation of these crops. The strategies involve four lines: selection of cultivars tolerant to water stress; use of bioinputs; adoption of direct planting and Crop-Livestock Integration (ILP); and use of suboptimal irrigation.

Rainfed agriculture (without any type of irrigation) occupies more than 90% of the country's agricultural area, according to lifting carried out by the Brazilian Institute of Geography and Statistics (IBGE) and by the National Water Agency (ANA). This type of planting, which depends entirely on rainfall and water stored in the soil, could be more productive if it weren't for the average annual water deficit of 37%. This number represents the lack of water for the full development of crops and was more significant in corn, which is often planted in regions and periods of greater climate risk. 

There is, therefore, a need for technologies that mitigate the effect of water stress and enable the optimized use of water. Irrigation seeks to eliminate the problem of reduced volume and instability of rainfall. However, it is still a distant reality for many farmers, as it increases the cost of production.

Help from genetics

“The first line, based on genetics and breeding, involves the use of genes that, in the acidic soils of the Brazilian Cerrado, allow root development in deeper layers, thus favoring water absorption and making crops more tolerant to water stress, ” details the Embrapa researcher Camilo Teixeira.

In the evaluation of cultivars, genes for tolerance to aluminum in the soil, which had already been identified in the laboratory, were tested in the field. “The field presented different levels of water availability in the soil and we detected that sorghum and corn hybrids containing aluminum tolerance genes showed gains in production stability and productivity under water stress”, reports the researcher Claudia Guimarães.

The use of an aluminum tolerance gene in corn hybrids in acidic soil resulted in productivity gains of 21% with full irrigation and 48% under water stress, in the grain filling phase (see article about). “With a deeper root system, corn plants better explore the subsurface layers of the soil, in conditions of irregular rainfall distribution in regions with acidic soils”, explains Guimarães. In these soils, corn production can be greatly reduced by the toxicity of aluminum, which impairs the exploration of the soil by the roots, reducing the uptake of water and nutrients and, consequently, grain production. 

Bioinputs and ILP

The second solution addresses the use of bioinputs, such as rhizobacteria, capable of stimulating root growth and, in this way, expanding the crop's ability to tolerate periods of water scarcity. Scientists tested growth-promoting bacteria alone and together. “The inoculation of corn with strains of Azospirillum brasilense or coinoculation with strains of Azospirillum brasilense and Bacillus contributed to the development and productive performance”, explains the researcher Isabel Prazeres.

The third solution focuses on the adoption of direct planting and Crop-Livestock Integration (ILP), aiming for the efficient use of water. The researcher Ramon Alvarenga explains that ILP has guaranteed good results, even in years with long periods of drought. "By recovering the soil's productive capacity, crops and pastures become more productive. The soil profile is corrected, with fertility monitoring, strategic use of correctives and fertilizers. Thus, the roots grow in depth and can explore better water and nutrients. The direct planting system helps with the infiltration and conservation of water in the soil, with the protection provided by straw. This way, the plants are able to maintain themselves without significant loss of productivity, even in the event of dry spells. " 

The fourth strategy covers the development of recommendations for the use of suboptimal irrigation, which consists of always applying less water than required, in the production of forage, silage and grains. In evaluations of this type of irrigation, corn, sorghum and millet crops tolerated reductions in irrigation depths without significant loss of fresh matter productivity. 

The deficit or suboptimal irrigation technique aims to restrict the amount of water applied without causing a significant loss of productivity. The use of this type of irrigation is an alternative to increase water use efficiency and guarantee production in times or places with low water availability.

Teixeira says that millet and sorghum tolerate greater water deficits than corn, although they produce less silage per hectare. Forage plants of the species Panicum maximum showed different responses to irrigation during periods of drought and annual rain. During the drought, all responded with growth and production, with the Massai and Tamani cultivars tolerating reduced irrigation without significant loss of dry matter production. “During the rainy season, supplementation promotes a response in production in the Kenya and Massai cultivars, being greater in the Kenya cultivar,” says researcher Teixeira.

Second Rosângela Simeão, researcher at Embrapa Beef Cattle, the use of suboptimal irrigation addresses the problem of forage production void during the period of water deficit. “In recent years, climate change has challenged the sustainability of agriculture. Seasonality in the production of tropical forage occurs annually, mainly due to the effects of drought. This has a negative impact on the efficiency of production systems, including those for meat and milk that depend on forage”, he states.

Cultivars used for intensive livestock farming were evaluated, with high productivity, but which significantly reduce forage production during the annual water deficit. “We tested three cultivars of Panincum maximum (Tamani, Kenya and Massai) against Cynodon (Tifton). The material that responded best to suboptimal irrigation was Kenya. Its productivity was equivalent to that obtained by Cynodon, which is the most used forage in the irrigated production system. This meets the economic demand of Brazilian producers”, explains the researcher. 

Os results indicate that the Massai, Tamani and Tifton cultivars produce forage with a 15% to 25% reduction in irrigation water, that is, they present high production efficiency. Kenya was the most productive cultivar of all during the water deficit, with a forage accumulation rate equivalent to 88% of the rate observed during the water surplus period.

“These results contribute to the maintenance and stability of bovine milk productivity throughout the year and also have the potential to promote greater annual weight gain in beef animals, increasing the efficiency and sustainability of the national livestock production system” , says Simeon. 

For Teixeira, studies demonstrate that suboptimal irrigation, in a scenario of constant water crises, has great potential to become a water-saving technology. Furthermore, the use of an aluminum tolerance gene has great potential for gaining grain production stability in acidic soils, with emphasis on second-crop cultivation, which is more affected by water deficit.

So that the results of research on the efficient use of water in agriculture reach a greater number of rural producers, the Technology Transfer team at Embrapa Milho e Sorgo produced a video about this work.

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