Deficit irrigation at different growth stages of the common bean (Phaseolus vulgaris L., cv. Imbabello)

Deficiência de água em diferentes estádios de desenvolvimento do feijoeiro (Phaseolus vulgaris L., cv. Imbabello)

Abstracts

To identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress, in which irrigation could be omitted without significant decrease hi final yield, two field experiments were conducted at "La Tola" University Experimental Station, Tumbaco, Pichincha, Ecuador, on a sandy loam soil (Typic Haplustoll). The climate is tempered and dry (mean air temperature 16°C and mean relative humidity 74%, during the cropping season) 123 and 109 mm of rainfall were recorded during the experimental cropping periods (July to October), of 1992 and 1994, respectively. The treatments consisted of combinations of 7 irrigation regimes including normal watering; full stress; (traditional management practice); single stress at vegetative stage; flowering; seed formation and ripening, and of 2 levels of applied N (20 and 80 kg/ha). These 14 treatment combinations were arranged and analysed in a split-plot design with 4 replications. The plot size was 33.6 m² (8 rows, 7 m long) with a plant population of 120,000 pl/ha. Irrigation treatments were started after uniform germination and crop establishment Soil water content was monitored with a neutron probe down to 0.50 m depth, before and 24 h after each irrigation. The actual evapotranspiration of the crop was estimated by the water-balance technique. Field water efficiency and crop water use efficiency were calculated. Yield data showed that the treatments which had irrigation deficit had lower yield than those that had supplementary irrigation. The flowering stage was the most sensitive to water stress. Nitrogen fertilization significantly increased the number of pods and gram yield. Crop water use efficiency (kg/m³) was the lowest with stress at the flowering period, and the yield response factor (Ky) was higher hi treatments of full stress and stress at flowering. In relation to the traditional management practice adopted by farmers, only treatments of normal watering and stress at maturation had 13 and 10% higher crop water use efficiency, respectively.

common bean; irrigation; water stress; water use efficiency


Com o objetivo de identificar estádios específicos de desenvolvimento do feijoeiro, nos quais a planta é menos sensível à deficiência de água e a irrigação poderia ser suprimida sem decréscimo significativo em produtividade, dois experimentos de campo foram conduzidos na Estação Experimental "La Tola", pertencente à Universidade Central de Equador, em Tumbaco, Pichincha, Equador. Os tratamentos consistiram de combinações de sete regimes de irrigação, incluindo a irrigação normal, deficiência completa, prática de manejo tradicional, deficiência no período vegetativo, deficiência na floração, deficiência na formação de vagens e deficiência no enchimento de grãos, e de dois níveis de fertilizante nitrogenado, 20 e 80 kg/ha. Essas quatorze combinações de tratamentos foram organizadas e analisadas segundo um delineamento estatístico de parcelas subdivididas, com quatro repetições. As parcelas foram de 33,6 m² (8 linhas de 7 m de comprimento, com uma população de 120.000 pl/ha. Os tratamentos de irrigação iniciaram-se após a germinação uniforme e estabelecimento da cultura. O conteúdo de água do solo foi monitorada com sonda de neutrons até a profundidade de 0,5 m, antes e 24 h após cada irrigação. A evapotranspiracão atual da cultura foi estimada pelo balanço hídrico. Calculou-se as eficiências de uso de água no campo e pela cultura. Dados de produtividade mostram que os tratamentos que tiveram deficiências apresentaram menor produtividade em relação a tratamentos com irrigação complementar. O estádio do florescimento foi o mais sensível à deficiência de água. A fertilização com N aumentou significativamente o número de vagens por planta e a produção de sementes. A eficiência de uso de água pela cultura (kg/m³) foi menor com deficiência na floração, e o fator de resposta à produtividade (kg) foi maior nos tratamentos de deficiência total e deficiência no florescimento. Considerando as práticas tradicionais de manejo utilizadas pelos agricultores, apenas os tratamentos de irrigação normal e de deficiência na maturação, tiveram uma eficiência de uso de água de 13 e 10% maior, respectivamente.

feijão comum; irrigação; deficiência de água; eficiência de uso de água


ARTICLES

Deficit irrigation at different growth stages of the common bean (Phaseolus vulgaris L., cv. Imbabello)

Deficiência de água em diferentes estádios de desenvolvimento do feijoeiro (Phaseolus vulgaris L., cv. Imbabello)

M. CalvacheI; K ReichardtII, III, V; O.O.S. BacchiIII, V; D. Dourado-NetoIV, V

IUniversidad Central del Ecuador, P. O. Box 2520 - Quilo - Ecuador

IICentro de Energia Nuclear na Agricultura/USP, C.P. 96, CEP: 13416-970 - Piracicaba, SP - Brazil

IIIDepto. de Física-ESALQ/USP, CP. 9, CEP: 13418-900 - Piracicaba, SP- Brazil

IVDepto. de Agricultura-ESALQ/USP, CP. 9, CEP: 13418-900 - Piracicaba, SP - Brazil

VBolsista do CNPQ

ABSTRACT

To identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress, in which irrigation could be omitted without significant decrease hi final yield, two field experiments were conducted at "La Tola" University Experimental Station, Tumbaco, Pichincha, Ecuador, on a sandy loam soil (Typic Haplustoll). The climate is tempered and dry (mean air temperature 16°C and mean relative humidity 74%, during the cropping season) 123 and 109 mm of rainfall were recorded during the experimental cropping periods (July to October), of 1992 and 1994, respectively. The treatments consisted of combinations of 7 irrigation regimes including normal watering; full stress; (traditional management practice); single stress at vegetative stage; flowering; seed formation and ripening, and of 2 levels of applied N (20 and 80 kg/ha). These 14 treatment combinations were arranged and analysed in a split-plot design with 4 replications. The plot size was 33.6 m2 (8 rows, 7 m long) with a plant population of 120,000 pl/ha. Irrigation treatments were started after uniform germination and crop establishment Soil water content was monitored with a neutron probe down to 0.50 m depth, before and 24 h after each irrigation. The actual evapotranspiration of the crop was estimated by the water-balance technique. Field water efficiency and crop water use efficiency were calculated. Yield data showed that the treatments which had irrigation deficit had lower yield than those that had supplementary irrigation. The flowering stage was the most sensitive to water stress. Nitrogen fertilization significantly increased the number of pods and gram yield. Crop water use efficiency (kg/m3) was the lowest with stress at the flowering period, and the yield response factor (Ky) was higher hi treatments of full stress and stress at flowering. In relation to the traditional management practice adopted by farmers, only treatments of normal watering and stress at maturation had 13 and 10% higher crop water use efficiency, respectively.

Key Words: common bean, irrigation, water stress, water use efficiency

RESUMO

Com o objetivo de identificar estádios específicos de desenvolvimento do feijoeiro, nos quais a planta é menos sensível à deficiência de água e a irrigação poderia ser suprimida sem decréscimo significativo em produtividade, dois experimentos de campo foram conduzidos na Estação Experimental "La Tola", pertencente à Universidade Central de Equador, em Tumbaco, Pichincha, Equador. Os tratamentos consistiram de combinações de sete regimes de irrigação, incluindo a irrigação normal, deficiência completa, prática de manejo tradicional, deficiência no período vegetativo, deficiência na floração, deficiência na formação de vagens e deficiência no enchimento de grãos, e de dois níveis de fertilizante nitrogenado, 20 e 80 kg/ha. Essas quatorze combinações de tratamentos foram organizadas e analisadas segundo um delineamento estatístico de parcelas subdivididas, com quatro repetições. As parcelas foram de 33,6 m2 (8 linhas de 7 m de comprimento, com uma população de 120.000 pl/ha. Os tratamentos de irrigação iniciaram-se após a germinação uniforme e estabelecimento da cultura. O conteúdo de água do solo foi monitorada com sonda de neutrons até a profundidade de 0,5 m, antes e 24 h após cada irrigação. A evapotranspiracão atual da cultura foi estimada pelo balanço hídrico. Calculou-se as eficiências de uso de água no campo e pela cultura. Dados de produtividade mostram que os tratamentos que tiveram deficiências apresentaram menor produtividade em relação a tratamentos com irrigação complementar. O estádio do florescimento foi o mais sensível à deficiência de água. A fertilização com N aumentou significativamente o número de vagens por planta e a produção de sementes. A eficiência de uso de água pela cultura (kg/m3) foi menor com deficiência na floração, e o fator de resposta à produtividade (kg) foi maior nos tratamentos de deficiência total e deficiência no florescimento. Considerando as práticas tradicionais de manejo utilizadas pelos agricultores, apenas os tratamentos de irrigação normal e de deficiência na maturação, tiveram uma eficiência de uso de água de 13 e 10% maior, respectivamente.

Descritores: feijão comum, irrigação, deficiência de água, eficiência de uso de água

INTRODUCTION

In Ecuador, the bean crop (Phaseolus vulgaris L.) is generally cultivated under rainfed conditions, in marginal lands in the semi-arid higlands (1800-3000m). Water stress is a very common problem during the growing period, exacerbated by the fact that the crop is planted in shallow soils with low nutrient and organic mater contents. The bean crop is grown during the part of the year when rainfall is expected, but alternate wet and dry periods of varying lengths affect the production potential. Common beans have a relatively shallow rooting depth, poor nodulation, require frequent irrigations (Miller & Gadner, 1972; Stansell & Smitle, 1980; Weaver et al., 1984; Calvache & Garcia, 1987) and large supplies of N fertilizers (Westerman et al., 1981; Calvache 1989; Castrillo et al., 1990). The increasing demands for limited water supplies and the rising costs of nitrogenous fertilizers lead to a rational use of these resources without adversely affecting production.

Cell expansion is one of the first growth processes affected by water stress. As a consequence, plants under severe stress are generally stunted. Leaf area, one of the main components of above-ground biomass, is also reduced by drought, due to reduced leaf area expansion and premature senescence (Salisbury & Ross, 1992). This process acts as a survival tactic, reducing the rate of water use and delaying the onset of more severe stress, but is generally irreversible. However, given favorable conditions, plants with an indeterminate growth habit, like cowpeas and dry beans, may late compensate for this loss of leaf area by producing new leaves.

As observed by Castrillo et al., (1990) water deficit can result in a sudden decrease in nitrate redutase activity and fluctuations in ammonium content. Protein content may show significant decrease under deficit, folowed by an increase with addition of water. Under moderate water deficit, an initial protein degradation can take place, followed by protein synthesis at the expense of accumulated reduced nytrogen; leaf protein is probably used as a source of reduced nitrogen for new protein synthesis.

Water requirements of the common bean has received very litle attention in Ecuador and therefore, the purpose of this study was to identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress and irrigation can be omitted without a significant decrease an final yield, and also to determine how irrigation deficits can affect fertilizer use efficiency.

MATERIALS AND METHODS

Two Field experiments were carried out at "La Tola" Agricultural Experimental Station in Tumbaco, Pichincha, Ecuador, on a Typic Haplustoll soil sandy loam texture (16% clay, 0.8% organic matter and pH 6.8). Seven waterstress treatments were tested at different growth stages (El- vegetative; E2- flowering; E3-Bean formation and E4- Ripening period), two levels of applied N-fertilizer (F1- 20 and F2- 80 kg/ha N) and two levels of irrigation: 1) Normal watering when real evapotranspiration was equal to the expected maximun (ETm); and 0) Deficit irrigation (aproximatly =1/2 ETm).

These combinations resulted in 14 treatments shown in TABLE 1.

Physical and chemical characterization of the soil and neutron probe calibration (Greacen, 1981), were carried out before actual experimental work was initiated. Bean seeds v. Imbabello were planted on July 3/1992 and July 2/1994. Plots of 33.6 m2, 8 furrows of 7 m (2 seeds per 25 cm ) were distributed in a split-plot design, with a plant population of 120,000/ha. Irrigation treatments started after uniform germination and crop establishment (Doorenbos & Kassan, 1979). Soil water content was measured with a neutron probe from 10 to 50 cm depth, before and 24 h after each irrigation, with measurements every 10 cm. Soil matric potential was monitored by installing tensiometers at 0.20m; 0.40 and 0.60 m, between plants in a crop row.

The actual evapotranspiration (ETa) of the crop was estimated by the water-balance technique and drainage or upward flow from ground water was calculated by Darcy equation. Field water efficiency (Ef=kg/m3) and crop water use efficiency Ec=kg/m ) were calculated dividing the actual grain yield (10% seed water content) y irrigation and by actual evapotranspiration (Eta), respectively (Doorenbos & Pruit, 1977; Hillel, 1990). Samples of 4 plants were collected at diferent growth stages and 50 plants at the time of final harvest, to determine dry matter and nitrogen content in leaf and stem, dry weight of pods harvested, number of pods and harvest index.

RESULTS AND DISCUSSION

The results of the physical analysis and the calibration of the neutron probe are shown in TABLE 2

TABLE 3 illustrates data of evapotranspiration calculated according to the modified Penman method and irrigation requirements for the treatment of normal watering (R1).

Deficit irrigation at different growth stages significantly influenced plants water evaporation and water balance (TABLES 4, 5, 6, 7, 8, 9, 10). Drainage or upward flow from ground water was practically insignificant and did not cause significant error in the estimate of actual evapotranspiration (Eta).

TABLE 11 show soil water storages down to the 0,50 m depth during the two experimental periods. It can be seen that water content increases after an irrigation or rain, depending on the treatment. Water storage in the treatment of full stress (IR2) was lower than in the treatment of normal watering (IR1). Generally water storage in all the treatments was higher than that of the treatment of full stress (IR2) in the stages in which irrigation was made, but lower than in the treatment IR1 which received irrigation during the entire cycle.

From the yield data presented in TABLES 12 and 13 it can be concluded that treatments which had irrigation deficit have lower yields than those that had supplementary rrigation (1% probability). The flowering stage was the mo)st sensitive to water stress. The treatment of stress at flowering stage (IR5) had the same result as the one which had water stress during the whole growing cycle (IR2), in the two experimental years (1992 and 1994). Comparing the results of fertiized treatments it can be seen that there are significant differences (1% probability) between the two fertilization levels used in the two experimental years (1992 and 1994). The interaction between irrigation and fertilization was only statistically different in the second experimental year (1994). The highest value was obtained in the treatment IR4F2. It can also be seen that the lower yields correspond to treatments IR5F2>IR5F1>IR2F2>R2F1 which is the reflex of the fact that common bean requires frequent irrigations and soil matric potential of -10 to -30 kPa for optimum growth (Miller & Gadner, 1972; Stansell & Smitle, 1980).

A highly significant difference was found in seed yield as an effect of water treatments. Results presented in TABLE 13 show that the seed weigth of teatments IR2 and IR3 were the lowest. In common beans a loss of reproductive organs can occur even under the most favorable conditions; this loss can be of different magnitudes in the same cultivar, depending on the environmental conditions. In the present study the quantity of reproductive organs shed during the development of the crop under the different water treatments was not measured, however a major shed of flowers and young pods was observed in the water stress treatments (IR2, IR3, IR5). Without exception, the yield components were dimished by the stress treatments, and this decrease was more severe in IR6 with the reduction of numbers of pods per plant and weigth of 100 seeds.

Aspinal & Paleg (1981) have enphatized that the organ wich is growing most rapidly at the time of the stress is the one most afected. For example, in the vegetive stage, the leaves and in rippening stage, the seeds. This relationship can actually lead to an increased harvest index (HI) under water stress because of strong reduction in vegetative growth. The treatment IR4 had HI of 0.59 , that is 18% over that of the control IR1. The nitrogen fertilization increased significantly the HI. Treatments F2 (80 kg N/ha) had HI 24% higer than of plants.Fl, in accordance to Albrech et al., (1984) and Hedge & Srinivas, (1990).

All stress treatments evaluated in this study reduced seed yield, however, as indicated, the highest reduction was found when the stress was imposed at the beginning of grain formation. This reduction in yield was due mainly to the reduction in the number of pods per plant. In this research, a small reduction in the number of seeds per pot and seed weigth was observed in treatments IR2 and IR7. The differences in yield among irrigation treatments could be attributed to the significant variations in the number of pods per plant. The improvement in yield with N fertilization was due to a significant increase in the number of pods per plants. Common bean being a poor nodulator, responds to the aplication of N.

To compare the two experiments, TABLE 14 presents the final data for the variables: field water use efficiency (Ef), crop water use efficiency (Ec) yield response factor (Ky) and relative yield response factor. Treatments IR1 and IR7 have more EC than the other due to the higher productivity. Treatment IR2 has higher Ef due to the small quantity of applied irrigation water during the crop cycle. The Ky is higher in treatments IR2 and IR5, and lower in treatments IR1 and IR7.

Water use of common bean was markedly influenced by the irrigation treatments. There was a decline in ETa with decreasing water content in the soil. This could be due to a combination of both, reduced surface soil evaporation with lower irrigation frequency and greater plant water deficits with low soil matric potentials. Water use efficiency, however, was maximun with deficit irrigation at the vegetative stage (IR4) and declined with irrigation frequency.

Relation to the traditional practice adopted by fanners of the region, only treatments IR1 and IR7 had 13 and 10% higher crop water use efficiency. The relative evaporation deficit (Ky) was lowest at the IR4 and higher at IR5 treatments.

CONCLUSIONS

Crop water use efficiency was the lowest at the flowering period and the yield reponse factor (Ky) was higher in treatment IR2 and IR 5. The flowering stage was the most sensitive to moisture stress. Nitrogen fertilization significantly increased the number of pods and grain yield.

Recebido para publicação em 01.04.97

Aceito para publicação em 15.04.97

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Publication Dates

  • Publication in this collection
    31 May 2005
  • Date of issue
    June 1997

History

  • Accepted
    15 Apr 1997
  • Received
    01 Apr 1997
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