INTRODUCTION
Rice (Oryza sativa L.) is the most important crop for human consumption, it constitutes the basic food for more than half of the world population (Ruiz et al., 2014). According to FAO, the world production of this crop has been increasing in recent years concentrated mostly in the main producing countries: China, India and Indonesia, which account for almost two thirds of world production (FAOSTAT, 2015).
In Cuba, this cereal is a basic food of the Cuban population, so that the national rice production does not satisfy domestic demand, hence more than 40% of this product, that is destined for the consumption of the population, is imported (Minag, 2014).
Water is one of the most important inputs for any crop and especially rice Jahan y Jesperson (2015); PUND (2016); the reduction in the use of this input, in addition to a sustainable increase in rice production in the country, is achieved by using the regrowth rice crop also known as soca or sapling.
One of the advantages of the shoot is that the production cycle is shorter than the main harvest. In addition, the production costs are substantially reduced, because the soil must not be prepared, leveled, sown, seed does not have to be acquired, and fertilizers are used in less quantity than in the main crop. Likewise, it requires less irrigation, because it ripens more quickly and the use of the land is more efficient, because erosion is avoided.
In the cooperative production sector, agricultural yields are reported, with the use of the regrowth crop, fluctuating between 2,5 and 4,27 t. ha -1 with excellent industrial grain quality, crystal clear grains, no white belly in the grain. In addition, the total production of several cultivars, such as INCA LP-5, INCA LP-7 and J-104, is higher than 10 t ha -1, being able to recommend them for use in production for this purpose (Castro et al., 2014).
In Cuba, in research carried out under both research and production conditions, a considerable reduction of irrigation water in this farming system is reported, up to 40% with a variety of medium cycle (Polón et al., 2012).
The realization of water stress to rice cultivation sometimes improves the yield, depending on the stage and the intensity of the stress, reaching the best results in the vegetative phase, not achieving the same results when applied in the reproductive phase of the crop, affecting also grain quality (Verma et al., 2014).
The objective of the present work was to evaluate the effect of water stress on the yield in the regrowth crop in INCA LP-5, a rice variety of short cycle.
METHODS
The research was conducted during four years, from 2014 to 2017 at the UCTB Los Palacios, on a Gleysol Nodular Ferruginous Petroferric soil (Hernández et al., 2015).
Treatments:
T 1. Regrowth with water stress to the crop in seedling phase, 10 days after the start of the regrowth with a stress duration of 15 days.
T 2. Regrowth without water stress to the crop in the seedling phase (production control)
The seeding density used was 120 kg. ha -1 (Minag, 2014).
For the development of the experiment, the INCA LP-5 short cycle commercial variety was used.
The cut made to the regrowth crop was from the soil surface to the desired height (AC).
Evaluations and measurements made:
Agricultural yield (t ha -1 to 14% humidity).
Industrial performance (% of whole grains).
Panicles per square meter
Water consumption (m 3. ha -1)
Water productivity (kg. m-3)
Water consumption was estimated from the delivery of each plot (20 L. s-1) according to the construction project of the irrigation system of Scientific Technology "Los Palacios", Pinar del Río Unit. For the industrial yield of the grain a sample of 1 kg of seed was taken, determining the percentage of whole grains. An experimental design of blocks was used at random, with two treatments, one with water stress and one without stress, which was maintained with a water sheet (10 cm) throughout its cycle, according to Minag (2014). Water stress was applied in the vegetative phase with wilting of the leaves, and the soil totally cracked.
The data obtained were subjected to an analysis of t-Student when significant differences were found between the means for the level of significance (p≤0.05).
RESULTS AND DISCUSSION
Among the factors affecting the yield of rice, they were found the moment of harvesting and the irrigation management, as both affect decreasing percentages of whole grains, the amount of panicles per square meter and other components that significantly affect agricultural culture performance and its industrial quality (Ruiz et al., 2014; de Avila et al., 2015). However, in this work, when the regrowth or soca culture was used and the irrigation was managed in a different way to the traditional (permanent water), that is, causing a water stress condition by default, the grain agricultural and industrial yield (% whole grains), panicles per square meter and a significant decrease in water consumption for the years of study.
The behavior of the panicles per square meter (Table 1) for the investigation period always showed higher values when the regrowth was cut at 5 cm from the soil surface, with respect to the cutting at height higher than 20 cm, regardless of whether the regrowth is without or with water stress. The latter, yield the greatest amount of panicles. m-2 , behavior that coincides with that reported by several authors (Polón et al., 1995; Polón y Castro, 1999).
Treatment | Panicles .m -2 | |||
---|---|---|---|---|
2014 | 2015 | 2016 | 2017 | |
Regrowth with water stress | AC- 5 cm- 370 a | AC- 5 cm - 240 a | AC- 5 cm -245 a | AC- 5 cm - 286 a |
AC- 20 cm-296 c | AC- 20 cm- 228 c | AC-20 cm-230 c | AC-20 cm -251 c | |
1,35 | 1,3 | 1,29 | 1,37 | |
Regrowth without water stress (control) | AC- 5 cm- 285 b | AC- 5 cm -220 b | AC- 5 cm - 240 b | AC- 5 cm - 266 b |
AC- 20 cm-222 d | AC-20 cm -189 d | AC-20 cm -225 d | AC-20 cm -200 d | |
1,32 | 1,27 | 1,26 | 1,34 |
Means with letters in common do not differ significantly according to Duncan's 5% test.
As it can be seen in Table 2, a significantly better performance of the agricultural yield was obtained, exceeding regrowth with water stress to regrowth without water stress (control). The former reached values that oscillate between 5,8 t. ha -1 and 5,0 t. ha -1, compared to 4,7 and 4,0 t. ha -1 (regrowth without water stress), and with the variant of cutting at 5 cm from the soil surface. This result coincides with that reported by Polón et al. (2012), when practicing equal cutting heights to the regrowth crop, which seems to indicate that, as the cut of the soca is lower, there is a favorable response in the crop in terms of its agricultural yield.
Treatment | Agricultural yield (t.ha -1 at 14% humidity) | |||
---|---|---|---|---|
2014 | 2015 | 2016 | 2017 | |
Regrowth with water stress | AC- 5 cm - 5,5 a | AC- 5 cm - 5,8 a | AC- 5 cm - 5,00 a | AC- 5 cm - 5,5 a |
AC- 20 cm- 3,1 c | AC-20 cm - 3,2 c | AC-20 cm - 4,00 c | AC-20 cm - 4,4 c | |
0,012 | 0,013 | 0,09 | 0,09 | |
Regrowth without water stress (control) | AC- 5 cm- 4,2 b | AC- 5 cm - 4,7 b | AC- 5 cm - 4,0 b | AC- 5 cm - 4,5 b |
AC-20 cm- 3,0 d | AC-20 cm -3,4 d | AC-20 cm -3,00 d | AC-20 cm - 3,3 d | |
0,011 | 0,011 | 0,08 | 0,089 |
Means with letters in common do not differ significantly according to Duncan's 5% test.
With a management of the irrigation and using the crop of regrowth with hydric stress, a high efficiency in the use of the water and a high productivity of the irrigation water is demonstrated (Table 3).
2014 | 2015 | 2016 | 2017 | |||||
---|---|---|---|---|---|---|---|---|
Treatment | Cons. of water (m3.ha -1) | Prod. of irrigation water (kg.m-3) | Cons. of water (m3.ha-1) | Prod. of irrigation water (kg.m-3) | Cons. of water (m3.ha-1) | Prod. of irrigation water (kg.m-3) | Cons. of water (m3.ha-1) | Prod. of irrigation water (kg.m-3) |
Regrowth with water stress | 4 100 | 1,34 | 5700 | 1, 01 | 4 1 90 | 1, 19 | 4 3 00 | 1, 27 |
Regrowth without water stress (control) | 5 800 | 0,72 | 6 800 | 0, 69 | 5 5 00 | 0, 72 | 6 2 00 | 0, 73 |
- | - | - | - | - | - | - | - |
The values reached in water consumption were always lower in the regrowth treatment with water stress, with values of 4100 m 3.ha -1 to 5700 m 3.ha -1, respectively, with respect to regrowth treatment without water stress (control). This latter showed the highest water consumption reported of 6 800 m 3.ha -1; however, it can be observed that the values of water resource savings oscillate in the order of 1700 and 1100 m 3. ha -1. These results coincide with those reported by the researchers Polón and Castro (1999) and Polón et al. (2012). They refer the benefits of water stress in the vegetative phase of the crop, with the use of regrowth and with a cutting height of 5 cm from the soil surface, since a greater economy of water is always reached, for being the greatest period without irrigation.
The values of water productivity ranging generally between 0,69 and 0,73 kg.m -3 for the control treatment (stress regrowth) and 1,34 kg.m -3 and 1,01 kg.m -3 for the regrowth with stress. These values are so high since the regrowth crop has a shorter cycle (70 days) and they differ much more than what was reported by Colom (2012) in Cuba of 0,31 kg.m -3 for long cycles (135 days). These values of water productivity, in turn, are located in the ranges of values reported by different authors (DIEA, 2014; de Avila et al., 2015; Ruiz et al., 2016; Riccetto et al., 2017).
Similar behavior presented the industrial yield of the grain (% of whole grains) as it can be seen in Table 4, where values of 63,9 % to 62,3 % of whole grains were reached in the treatment with water stress and without. However, in the control it was 64,9 % to 61,8 % whole grains, both for a cutting height of 5 cm. These values demonstrate once again the benefit of applying water stress in the increase of agricultural yield without affecting the industrial quality of the grain, as reported by several researchers (Polón and Castro, 1999; Polón et al., 2012; Castro et al., 2014; Ruiz et al., 2014; Bergson et al., 2015).
Treatment | Industrial yield (% of whole grains) | |||
---|---|---|---|---|
2014 | 2015 | 2016 | 2017 | |
Regrowth with water stress | AC- 5 cm- 63,3 a | AC- 5 cm - 63,9 a | AC- 5 cm - 62,3 a | AC- 5 cm - 63,8 a |
AC-20 cm- 60,0 c | AC-20 cm - 60,8 c | AC-20 cm - 60,2 c | AC-20 cm - 60,9 c | |
1,85 | 1,86 | 1,82 | 1,29 | |
Regrowth without water stress (control) | AC- 5 cm- 64,9 b | AC- 5 cm - 62,8 b | AC- 5 cm - 61,8 b | AC- 5 cm - 61,5 b |
AC-20 cm- 61,1 d | AC-20 cm - 60,4 d | AC-20 cm - 59,2 d | AC-20 cm - 58,6 d | |
1,89 | 1,84 | 1,79 | 1,27 |
Means with letters in common do not differ significantly according to Duncan's 5% test.
CONCLUSIONS
It can be concluded that, when irrigation is managed in rice cultivation for the short-cycle variety INCA LP-5, in a different way to the traditional (permanent water), that is, causing a water stress condition by default, cultivation in the vegetative phase, with regrowth and under 5cm regrowth cutting height, the agricultural yield is increased by approximately 0,5 t. ha-1. In addition, the industrial yield of the grain improves with values higher than 63 % whole grains, and the number of panicles per square meter, with respect to the regrowth without water deficit (control).
Moreover, lower water consumption is achieved in favor of the regrowth treatment with water stress, compared to the control, with a water resource saving of approximately 1700 m3. ha-1, which leads to a high productivity of irrigation water in the new treatment.