ABSTRACT

Coffee crop, highly important worldwide, is one of the main commodities in Brazilian exports. However, due to climate changes, its cultivation is currently demanding irrigation techniques. Current assay evaluates the effect of different irrigation water levels on the development and productivity of coffee shrubs in predominant soil and climate conditions of the town of Muzambinho, in the southern region of the state of Minas Gerais, Brazil. The experiment was performed in July 2013 on a coffee plantation, planted with coffee shrubs, cultivar Red Catuaí IAC/144, by drip irrigation. Experiment design consisted of randomized blocks with four replications and four treatments, or rather, different irrigation water depths: 0 (without irrigation), 50, 100 and 125% of ET₀. Productivity, vegetal growth and distribution of the radicular system were evaluated after 12 months. Treatments did not affect vegetal growth. Better quantity and distribution of the radicular system were detected at 100% irrigation level, with a productionof 55 sacks.ha^-1 or a 45% gain when compared to that in non-irrigated areas.

Key words: Management, coffee, drip system.

Features of the experimental area

 

The experiment was conducted on the coffee culture experimental area of the Instituto Federal de Educação, Ciência e Tecnologia do Sul de Minas Gerais – Campus Muzambinho (IFSULDEMINAS), in the municipality of Muzambinho, in the southern region of the state of Minas Gerais, Brazil. According to Koppen’s classification, the region’s predominant climate is Cwb, with mean annual temperature at 18°C and mean yearly rainfall 1605 mm. The central point lies at 21° 21’ 01.07’’S and 46° 31’ 21.10’’W, at a mean altitude 1100 m.

 

Planting of 360 six-month-old coffee seedlings (Coffea arabica L.) var. Red Catuaí (IAC/144), with excellent phytosanitary conditions, occurred on January 2012. There was 3.0 spacing between the rows and 1.00 between the holes, totally 3333 plants per hectare, in an area 64.5 m long and 21.5 m wide, approximately totaling 1344 m².

 

Irrigation

 

The plants were irrigated three times a week by a localized irrigation system, with auto-compensating drip emitters, at a discharge of 1.3 L.h^-1 at every 30 cm, with a single irrigation row under the surface of each coffee shrub row.

 

Conditions tested in current experiment did not allow the application of FAO Peaman-Monteith method. However, empirical methods comprising mass transference, temperature and evaporation-based methods have been applied to estimate ET0. In fact, several research works show the efficiency of such methods (Valipour, 2014c, d, e, f, g, h, i, j, k; Valipour, 2015a, b, c). Applied water levels were calculated by Equation (1) with 0.9 efficiency, following Montovani (2011). Water excess in the soil was not reported during the experiment. Reference Evapotranspiration (ET₀) was calculated by the Penman-Monteith. Depths were calculated according to rainfall and water balance of the soil (Allen et al., 1998) (Figure 3b). The sum of ET₀ was performed every three days subtracting rainfall amounts.

 

 

Vegetal characteristics

 

After the start of treatment applications, the monthly evaluations on the vegetal growth of the plants were undertaken throughout the experiment, between July 2013 and July 2014, comprising height of plant (HP), measured by a graded bar from the soil surface to the tip of the plant, in cm; diameter of canopy (DC), measured by a graded bar at the height of the third middle of the plant and perpendicular to the row [cm]; number of primary plagiotropic branches (NPPB), measured all the plagiotropic branches in the plants. Radicular growth was measured by an auger drill at depths 20, 40 and 60 cm and at two distances from the trunk, at 20 and 50 cm, on July 2014.  

 

Productivity and quality of the coffee plants

 

After the harvest of the experimental parcels, samples of coffee from cloth-sieve were retrieved and dried daily until moisture reached 11 to 12%. After drying, the samples were weighed, processed and weighed again. Data from all the process phases were used to calculate productivity, expressed in 60 kg of coffee per hectare.

 

Samples were removed from the processed volume for type and sieve classification. Grain size classification was undertaken in samples of 300 g and obtained by grain percentages in circular sieves (16 mm).

 

Statistical analyses

 

Evaluation results underwent analysis of variance (ANOVA) by F-test; when results were significant, means were compared by Scott & Knott test  at  5%  significance, with SISVAR (Ferreira,  2011).

Vegetal growth was not affected by treatments, or rather, there were no significant effects on plant height, number of plagiotropic branches and crown diameter by F-test (p<0.05). The variables height of plant, the number of plagiotropic branches and crown diameter did not behave differently with different water regimes.

 

Figure 2 gives details on the equations of vegetal growth for treatment Li 3 = 100% ET₀, taking into consideration height of plants, crown diameter and number of plagiotropic branches versus time, coupled to the result of the regression test for this parameter with coefficient of determination at 97.7, 99.9 and 99.5%. 

 

 

Linear behavior and higher growths were reported for the variable height and number of plagiotropic branches; a linear and quadratic adjustment was registered for the crown diameter.

 

Height of plant reached 115 cm, with a 35% growth during the year. The crown diameter reached 120 cm with 62 plagiotropic branches during the same period, featuring respectively a yearly growth of 35 and 70%. In their research on different cultivars of irrigated coffee shrubs in the savannah of Goiás, Brazil. Oliveira et al. (2004) reported heights between 111 and 120 cm and 47 to 50 plagiotropic branches per plant of the 24-month-old cultivar Red Catuai. Vegetal growth was similar to that in current analysis.

 

Rezende et al. (2010) reported a positive irrigation effect on plant growth with regard to height and crown diameter in 457-day-old Obatã-IAPAR-59 cultivar. Carvalho et al. (2006) also registered that the crown diameter of the coffee shrub cultivar Rubi  MG-1192  was also affected by irrigation, underscoring its benefits in the development of coffee cultivation.

 

Figure 3 gives data on rainfall, evapotranspiration (ET), water storage and irrigation depth between July 2013 and June 2014. Irrigation depths did not influence the vegetal growth, probably due to the good water conditions of the soil assessed between July and mid-September 2013. On the other hand, the soil suffered a water deficit from October till the end of November. In December, the soil’s water deficit decreased significantly due to rainfall increase, with good water conditions during approximately four months, from July to December 2013. This fact may have contributed towards the development of the plants within the crop´s vegetal growth phase. 

 

Irrigation affected the distribution of the radicular system (p<0.05). As a rule, roots had a greater concentration at a distance of 20 cm from the trunk, or rather, practically for the projection of the coffee plants’ crown (Figure  4).  A decrease  in  the  number  of  roots occurred in most treatments when distance increased to 50 cm from the trunk. At a depth up to 60 cm, there was a decreasing trend in the quantity of roots  in  the   treatment   with   plants growing without any irrigation water.

 

According to Carducci et al. (2014), the greatest concentration of the coffee shrub’s radicular system  occurs  with  the  crown  projection  band, predominantly at depths between 20 and 34 cm, corroborating results obtained in control as those with different irrigation water depths.

 

The treatment with 100% irrigation water depth (Li 03) tended towards a greater number of roots distributed at a 20 to 50 cm distance from the trunk and at a 20 to 60 cm in depth. The treatment with the combination 50 cm distance and 40 to 60 cm depth was better than the others; similarly, at a distance of 20 cm from the trunk and at a depth of 20 cm.

 

 

There was a decrease in the radicular system in treatment with 50% irrigation water depth at a distance of 50 cm from the trunk for all soil depth evaluated and in all treatments studied. Growth decrease in the radicular system, even when compared to control treatment (without any irrigation water), may be related to the re-translocation process of photo-assimilates for the aerial section of the coffee shrub in this treatment, aiming to maintain the high productivity reported (57 sacks ha^-1), statistically equal to treatment with 100% of water irrigation depth (Table 1).

 

There was probably better water distribution in the treatment 100% irrigation water depth (Li 03) at a 20 cm distance from the trunk. This was due to the dripper which formed a moist bulb with an amount of water close to the ideal for the coffee shrub and which contributed towards a higher radicular growth with the sampled band. In the sample 50 cm from the trunk, there occurred a natural decrease in water availability, with a decrease in the radicular system. Similar results were verified by Barreto et al. (2006) in a drip irrigated coffee plantation. According to these authors, high water rate in the soil interferes in radicular aeration and respiration, besides making difficult the passage of ethylene produced by the radicular system, and by soil pores, jeopardizing root growth. The above may explain the behavior  of  radicular growth in treatment 125% of irrigation water depth (Li 04) in current analysis (Figure 4).

 

Characteristics of production

 

Table 1 shows a summary of the analysis of variance for the productivity of processed coffee for the 2012 harvest.

 

There was a significant effect (p<0.05) for all evaluated production attributes.

 

Table 1 reports the analysis of variance for granulometry and demonstrates that irrigation water depths applied according to ET₀ percentage affected significantly the granulometry of the coffee grains.

 

Irrigation at 100% water irrigation depth provided 74% of over 16-sieve coffee grains, registering the best result for the variable. It is actually about 8% more grain than that of other treatments, which is highly beneficial from the commercial point of view, since over 16-sieve grains are better classified on the market.

 

Processed coffee production derived from irrigation Li 03 (100% ET₀) was higher when compared to treatment without irrigation and to treatment 120% of ET₀. It was statistically equal to coffee with 50% ET₀, with rates between 1.01 and 1.05 kg plant^-1, with no difference by Scott-Knott test at 5% probability. In fact, irrigation enhanced an approximately 60% increase of processed coffee per plant when compared to plants without irrigation. The performance of the treatments 50 and 100% irrigation water depths for the variable processed coffee provided the highest productivity rates which varied between 55 and 57 sacks ha^-1, respectively between 16 and 18 surplus coffee sacks, or a 45% gain when compared to the productivity of plants without any irrigation water.

 

Harvest provided a mean productivity of 55.36 sacks per hectare (Li 03), which is excellent productivity, when the importance of coffee productivity for the coffee producer´s economic return is so relevant. It should also be verified whether the productivities obtained are the first produce of the coffee plantation.

 

Productivity decreases as the irrigation water depth increases, till it reaches 45.38 sacks per hectare with Li 04 (125% ET₀). Decrease in the productivity of irrigated plants at depth over 100% ET₀ may be due to the excessive water application at the region of the radicular system of the culture and, consequently, the leaching of nutrients with the irrigation water at the soil’s deepest layers. Therefore, increase in water volume to the coffee plants does not necessarily mean an increase in productivity.

 

In current analysis, the non-irrigated treatment had the lowest productivity and showed that irrigation in coffee plants in the region of Muzambinho MG Brazil is advantageous, corroborating results by Oliveira et al. (2010) and Silva et al. (2011).

 REFERENCES