Fertigation in sugarcane

The use of nitrogen via Irrigation water in a central pivot system can bring several benefits to sugarcane fields. Increased productivity and improvements in quality indexes raw material stand out. Its use, however, needs to occur in a rational, with attention to social and ecological aspects of the region, at the same time which helps to make the activity more profitable.

A Sugarcane cultivation is quite demanding regarding nutrition. The nitrogen (N) is required in large quantities for biomass production. Average 1,4 kg of N per ton of straw produced. It is among the mineral nutrients applied to the production of sugar cane in Brazil, the most expensive, and fertilized amounts of N fertilizer are generally equal to or less than the exported by the culms. Its deficiency causes a reduction in the synthesis of chlorophyll, essential amino acids and the energy necessary for the production of carbohydrates and carbonic skeletons, directly reflecting on the development and crop yield.

Fertigation is a technique that has The objective is to apply fertilizers in liquid form, together with the irrigation water, optimizing the irrigation system, which most of the time has a high cost. This operation is very useful for plants, because the fertilizer is supplied with the water being applied to the soil (essential for its absorption). It also has many other advantages, such as better distribution of fertilizer in the field, reduced costs, reduced soil compaction, greater application flexibility, possibility of application in critical times and reduction of mechanical damage to the crop.

The use of fertigation has, therefore, general, the characteristic of improving the efficiency in the use of nutrients, for be applied in fractions, according to the rate of nutrient absorption of culture. The application of fertilizers via irrigation water must follow the recommendations for application period, frequency, doses and sources ensuring, In this way, an adequate supply of water and nutrients in the root zone of the plant.

Working with the hypothesis that the source and supply of nitrogen via irrigation water influence the cultivation of sugar cane in the Cerrado region, was study was carried out to evaluate the productivity, quality and yield of irrigated sugar cane subjected to different doses of fertigation nitrogen via central pivot system in the sugarcane-plant cycle in an oxisol clayey dystrophic red, cerrado phase.

The experiment

The experiment was conducted under field conditions, in an area of ​​the Rio Paraiso II farm belonging to the Raízen Plant, in the municipality of Jataí, Goiás. The coordinates geographic locations are 17°44'2.62"S and 51°39'6.06"W, with altitude average of 907 m. According to the classification of Köppen & Geiger (1928), the climate The location is of the Aw type, tropical, with rain from October to April, and dry in the months of May to September. The temperature maximum ranges from 35ºC to 37ºC, and the minimum from 12ºC to 15 ºC (in winter there is occurrences of up to 5th degrees). The precipitation annually reaches approximately 1.800 mm, but poorly distributed throughout of the year. The soil of the area experimental is classified as a dystrophic Red Oxisol, very clayey.

The experimental design used It was random blocks. The factors evaluated consisted of four doses of N applied via fertigation (0 kg/ ha, 60 kg ha, 120 kg ha and 180 kg ha), divided into four monthly applications starting 60 days after the planting.

All the treatments were fertilized in the planting furrow with phosphorus P2O5 (100 kg/ ha) in the form of triple superphosphate, potassium K2O (80 kg/ha) in the form of potassium chloride, and micronutrients, according to results soil analysis and recommendation.

Soil preparation was carried out by conventional system, through plowing and harrowing, followed by opening the mechanized planting furrows. The variety implemented in the experiment was IACSP95-5000, under sugarcane conditions, planted on 05/08/2014. The deals cultural issues relating to the use of herbicides, insecticides, fungicides and other products related to the control of invasive plants, pests and diseases were used according to the need and assessment of infestation, and in accordance with the practices adopted by Usina Raízen.

Irrigation and fertigation was carried out by a central pivot brand ZIMMATIC, model PC 08-64/03-647/01-646/L4 + AC, in galvanized steel, low pressure, with 12 support towers, with a total irrigated area of ​​139,31 hectares, speed of 268 m/h in the last tower, applies a minimum rough edge for a 100% turn of 1,35 mm. The piping pipeline is 800m long, with a diameter of 162,2 mm made of PVC 150/60. Pressurized by a simple IMBIL pump model ITA 100-400, with flow forecast of 128,99 m3 h, and forecast pressure of 63,90 mca, rotation of 1750 rpm and engine power of 47,49 hp. To carry out fertigation, it was A system coupled to the pivot containing two reservoir boxes was used to fertilizer dilution and a pumping system for fertilizer injection fertilizer diluted in the center pivot. A 3 mm blade was used in the time of fertigation.

A Harvest was carried out on 25/08/2015. Straw productivity was determined through total weighing of the stalks present in the respective plots, The weight of the stalks was quantified, the value of which was extrapolated to t/ha. The parameters of sugarcane quality were determined in the factory's own laboratory. You industrial yield values ​​were calculated based on the parameters of stalk quality and productivity. The results were submitted to analysis of variance using the F test at a 5% probability level, and in cases of significance, regression analysis was performed for fertigation levels nitrogen, using the software SISVAR statistician.

Results and discussion

Stalk productivity (PC) increased linearly 40,22% due to nitrogen fertigation, reaching a productivity maximum of 142,55 t/ ha at a dose of 180 kg/ ha of N, with each 1 kg/ ha of N promoted an increase of 0,7919 t/ha in PC (Figure 1A). Total sugars recoverable resources (ATR) increased by 5,16%, due to nitrogen fertigation via irrigation water, with an ATR value of 140,77 kg/t at a dose of 180 kg/ ha of N, with each 1 kg/ ha of N promoting an increase of 0,7820 kg/ t in ATR (Figure 1B). Gross sugar yield (RBAÇ) increased linearly 43,31% due to nitrogen fertigation via irrigation water, such so that at a dose of 180 kg/ha of N it achieved a yield of 20,32 t/ha, with each 1 kg/ha of N providing an increase of 0,1129 t/ha in RBAÇ (Figure 1C). The gross alcohol yield (RBAL) increased by 43,20% due to nitrogen fertigation via irrigation water, reaching 14,50 m3 ha at a dose of 180 kg/ha of N, with each 1 kg/ha of N provided an increase of 0,0805 m3 ha in RBAL (Figure 1D). A nitrogen fertigation promoted significant increases in all variables production analyzed.

In Brazil, experiments carried out in Field conditions, with application of urea on sugarcane straw, have shown losses due to ammonia (NH3) volatilization that can reach 20% at 40% or more of the N applied. Similar data have been reported in other sugarcane producing regions of the world. The use of fertigation mitigates the problem of NH3 gaseous losses and can contribute to increasing the water and fertilizer N use efficiency. Fertigation, in addition to increasing crop productivity, sugarcane, promotes improvements in the quality indexes of the raw material. That practice is still not widespread, but its benefits for culture are several. However, the application of nutrients via irrigation water in cultures must be managed rationally, considering social aspects and ecological aspects of the region, seeking to maximize the productivity and efficiency of use of the nutrient and minimize costs, both labor and capital, in order to make the activity profitable. Fertigation must be carried out with the objective of increasing profit and productivity, in quantity and quality.

Box – Sugar cane

The sugar cane (Saccharum officinarum L.) has been cultivated in Brazil since the 16th century and expanded in the country, being used in the production of sugar for consumption domestic and export, generating foreign exchange for the country, and acquired a large economic importance, due to the great demand for bioenergy, production of clean and renewable fuel, replacing fuels derived from Petroleum. Brazil is the world's largest producer of sugar cane and its derivatives, sugar and alcohol, favored by its extensive area and the climate suitable for vegetable production throughout the year.

The area harvested from sugarcane destined for sugar and alcohol activities in the 2015/16 harvest was 8.654,2 thousand hectares. São Paulo, the largest producer, has 52% (4.498,3 thousand hectares), followed by Goiás with 10,4% (885,8 thousand hectares), Minas Gerais with 10,1% (866,5 thousand hectares), Mato Grosso do Sul with 7% (596,8 thousand hectares), Paraná with 6% (515,7 thousand hectares), Alagoas with 3,7% (323,6 thousand hectares), Pernambuco with 3% (254,2 thousand hectares) and Mato Grosso with 2,7% (232,8 thousand acre). These eight states are responsible for 94,9% of national production. The other 14 producing states have areas smaller than 1% of the total area of country, totaling 5,1% of the country's total area.

The growth of cultivation of sugarcane cultivation in the central-west region has been increasing not only due to the expansion of agricultural areas, but also due to the increase in productivity, however, it is of fundamental importance to apply new techniques for optimizing the sector, with regard to the evolution technology, in order to provide a continuous increase in rates of productivity per area, since the crop has great potential productive.

Article published in issue 220 of Cultivar Grandes Culturas, September, 2017.