Deficit irrigation scheduling based on plant growth stages showing water stress tolerance

C. Kirda,
Cukuroya University,
Adana, Turkey

Summary

With increasing municipal and industrial demands for water, its allocation for agriculture is decreasing steadily. The major agricultural use of water is for irrigation, which, thus, is affected by decreased supply. Therefore, innovations are needed to increase the efficiency of use of the water that is available. There are several possible approaches. Irrigation technologies and irrigation scheduling may be adapted for more-effective and rational uses of limited supplies of water. Drip and sprinkler irrigation methods are preferable to less efficient traditional surface methods. It is necessary to develop new irrigation scheduling approaches, not necessarily based on full crop water requirement, but ones designed to ensure the optimal use of allocated water. Deficit (or regulated deficit) irrigation is one way of maximizing water use efficiency (WUE) for higher yields per unit of irrigation water applied: the crop is exposed to a certain level of water stress either during a particular period or throughout the whole growing season. The expectation is that any yield reduction will be insignificant compared with the benefits gained through diverting the saved water to irrigate other crops. The grower must have prior knowledge of crop yield responses to deficit irrigation. This paper reviews yield responses of major field crops to deficit irrigation, including cotton, maize, potato, sugar cane, soybean and wheat. Crop yields obtained under various levels of reduced evapotranspiration were fitted to the linear crop yield response functions of Stewart et al. (1977). Results show that cotton, maize, wheat, sunflower, sugar beet and potato are well suited to deficit irrigation practices, with reduced evapotranspiration imposed throughout the growing season. This list may also include common bean, groundnut, soybean and sugar cane where reduced evapotranspiration is limited to (a) certain growth stage(s). With a 25 percent deficit, WUE was 1.2 times that achieved under normal irrigation practices. Irrigation scheduling based on deficit irrigation requires careful evaluation to ensure enhanced efficiency of use of increasingly scarce supplies of irrigation water.

General concepts and rationale

In the past, crop irrigation requirements did not consider limitations of the available water supplies. The design of irrigation schemes does not address situations in which moisture availability is the major constraint on crop yields. However, in arid and semi-arid regions, increasing municipal and industrial demands for water are necessitating major changes in irrigation management and scheduling in order to increase the efficiency of use of water that is allocated to agriculture.

Agronomic measures such as varying tillage practices, mulching and anti-transpirants can reduce the demand for irrigation water. Another option is deficit irrigation, with plants exposed to certain levels of water stress during either a particular growth period or throughout the whole growth season, without significant reduction in yields.

Much published research has evaluated the feasibility of deficit irrigation and whether significant savings in irrigation water are possible without significant yield penalties. Stegman (1982) reported that the yield of maize, sprinkler irrigated to induce a 30 - 40 percent depletion of available water between irrigations, was not statistically different from the yield obtained with trickle irrigation maintaining near zero water potential in the rootzone. Ziska and Hall (1983) reported that cowpea had the ability to maintain seed yields when subjected to drought during the vegetative stage provided subsequent irrigation intervals did not exceed eight days. The work of Korte et al. (1983), Eck et al. (1987), Speck et al. (1989), and of many others, has shown that soybean is amenable to limited irrigation. Stegman et al. (1990) indicated that although short-term water stress in soybean during early flowering may result in flower and pod drop in the lower canopy, increased pod set in the upper nodes compensates for this where there is a resumption of normal irrigation.

Cotton shows complex responses to deficit irrigation because of its deep root system, its ability to maintain low leaf water potential and to osmotically regulate leaf-turgor pressure, i.e. so-called conditioning. Thomas et al. (1976) found that plants that suffered a gentle water stress during the vegetative period showed higher tolerance of water deficit imposed later as a result of adaptation to existing soil water status. Grimes and Dickens (1977) reported that both early and late irrigations lowered cotton yields. However, water stress during vegetative growth, causing leaf water potential less than a critical midday value of -1.6 MPa , adversely affected the final yield (Grimes and Yamada, 1982).

Similar work on sugar beet (Okman, 1973; Oylukan, 1973; and Winter, 1980), sunflower (Jana et al., 1982; Rawson and Turner, 1983; and Karaata, 1991), wheat (Day and Intalap, 1970; and Musick and Dusck, 1980), potato (Bartoszuk, 1987; Trebejo and Midmore, 1990; and Minhas and Bansal, 1991) and on many other crops has demonstrated the possibility of achieving optimum crop yields under deficit irrigation practices by allowing a certain level of yield loss from a given crop with higher returns gained from the diversion of water for irrigation of other crops. Where water scarcity exists at the regional level, irrigation managers should adopt the same approach to sustain regional crop production, and thereby maximize income (Stegman et al., 1980). This new concept of irrigation scheduling has different names, such as regulated deficit irrigation, pre-planned deficit evapotranspiration, and deficit irrigation (English et al., 1990).

Furthermore, yield reductions from disease and pests, losses during harvest and storage, and arising from insufficient applications of fertilizer are much greater than reductions in yields expected from deficit irrigation. On the other hand, deficit irrigation, where properly practised, may increase crop quality. For example, the protein content and baking quality of wheat, the length and strength of cotton fibres, and the sucrose concentration of sugar beet and grape all increase under deficit irrigation.

Deficit irrigation management

Deficit irrigation practices differ from traditional water supplying practices. The manager needs to know the level of transpiration deficiency allowable without significant reduction in crop yields. The main objective of deficit irrigation is to increase the WUE of a crop by eliminating irrigations that have little impact on yield. The resulting yield reduction may be small compared with the benefits gained through diverting the saved water to irrigate other crops for which water would normally be insufficient under traditional irrigation practices.

Before implementing a deficit irrigation programme, it is necessary to know crop yield responses to water stress, either during defined growth stages or throughout the whole season (Kirda and Kanber, 1999). High-yielding varieties (HYVs) are more sensitive to water stress than low-yielding varieties; for example, deficit irrigation had a more adverse efect on the yields of new maize varieties than on those of traditional varieties (FAO, 1979). Crops or crop varieties that are most suitable for deficit irrigation are those with a short growing season and are tolerant of drought (Stewart and Musick, 1982).

In order to ensure successful deficit irrigation, it is necessary to consider the water retention capacity of the soil. In sandy soils plants may undergo water stress quickly under deficit irrigation, whereas plants in deep soils of fine texture may have ample time to adjust to low soil water matric pressure, and may remain unaffected by low soil water content. Therefore, success with deficit irrigation is more probable in finely textured soils.

Under deficit irrigation practices, agronomic practices may require modification , e.g. decrease plant population, apply less fertilizer, adopt flexible planting dates, and select shorter-season varieties.

Deficit irrigation scheduling

Discussions in this section are based on data from a coordinated research programme (CRP) on crop yield responses to deficit irrigation Kirda et al., 1999b, conducted under the auspices of the Soil and Water Management and Crop Nutrition Section of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna. A wide range of field crops (including cotton, wheat, sugar beet, soybean, sugar cane, potato, and maize) were the subject of four years of field experiments. Crop yield response data from deficit irrigation were fitted to the following linear equation used earlier by Stewart et al. (1977):

    (1)

where Y and Y_m are expected and maximum crop yields, corresponding to ET_a and ET_m, actual and maximum evapotranspiration, respectively; k_y is a crop yield response factor that varies depending on species, variety, irrigation method and management, and growth stage when deficit evapotraspiration is imposed. The crop yield response factor gives an indication of whether the crop is tolerant of water stress. A response factor greater than unity indicates that the expected relative yield decrease for a given evapotraspiration deficit is proportionately greater than the relative decrease in evapotranspiration (Kirda et al., 1999a). For example, soybean yield decreases proportionately more where evapotranspiration deficiency takes place during flowering and pod development rather than during vegetative growth (Figure 1).

Figure 1
Relative seed yield response of soybean to relative ET deficit

Table 1 summarizes crop response factors that are less than unity for situations where deficit irrigation practices may seem to be acceptable and an infeasible option either for the season or for a particular growth stage. Under the defined conditions, the relative yield decrease was proportionately less than the decreased application of irrigation water. Therefore, one should expect crop WUE (E_c) to increase even if crop yields fell. The equation for crop WUE is:

    (2)

where:
Y = crop yield (kg/ha)
ETa = actual evapotranspiration (mm)

Table 1
Crop response factors where yield reduction is proportionally
less than relative evapotranspiration deficit

Alternatively, the equation for crop WUE can be derived from Equation (1):

    (3)

where E_c varies depending on crop response factor. Diverting the saved water to increase the area irrigated may compensate for decreases in crop yields. Table 2 shows probable increases in irrigation WUE, corresponding to a 25 percent relative evapo-transpiration deficit for the main field crops. Estimates of relative crop yields were made where yield decreases were less than relative evapo-transpiration deficits. For example, an expected yield was 82 percent for maize for the 25 percent relative ET deficit, when it prevailed for the whole growing season (Table 2).

Table 2
Expected relative yield and relative water use efficiency, for a planned
evapotraspiration deficit of 25 percent

The field crop WUE was 1.09 times higher than when no ET deficit occurred. This suggests that increasing the areas irrigated with the water saved would compensate for any yield loss. If the planned ET deficit is imposed throughout the season, it is possible to calculate the total irrigation water saved if one knows total crop water requirement. However, if the stress is imposed during a specific growth stage, one needs to know the total water requirement (i.e. crop water consumption) during that stage to quantify the water saved. As crop yield response factor (k_y) increases, field WUE decreases, which in turn implies that benefit from deficit irrigation is unlikely. Figure 2 shows interrelations between field WUE, crop yield response factor, and planned ET deficit. Only those crops and growth stages with a lower crop yield response factor (k_y<1.0) can generate significant savings in irrigation water through deficit irrigation.

Figure 2
Dependence of crop field water use efficiency on the crop yield
response factor and planned ET deficit, percentage values

Conclusions

The proper application of deficit irrigation practices can generate significant savings in irrigation water allocation. Among field crops, groundnut, soybean, common bean and sugar cane show proportionately less yield reduction than the relative evapotraspiration deficit imposed at certain growth stages.

Crops such as cotton, maize, wheat, sunflower, sugar beet and potato are well suited for deficit irrigation applied either throughout the growing season or at pre-determined growth stages. For example, deficit irrigation imposed during flowering and boll formation stages in cotton, during vegetative growth of soybean, flowering and grain filling stages of wheat, vegetative and yielding stages of sunflower and sugar beet will provide acceptable and feasible irrigation options for minimal yield reductions with limited supplies of irrigation water. This work may provide guidelines for practising deficit irrigation for identifying likely growth stages for imposing reduced ET, and for assessing the economic feasibility and acceptability of deficit irrigation through the estimation of expected relative yield decreases.

References

Ahmad, A. 1999. Yield response of groundnut grown under rainfed and irrigated conditions. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Anac, M.S., Ali Ul, M., Tuzel, I.H., Anac, D., Okur, B. & Hakerlerler, H. 1999. Optimum irrigation scheduling for cotton under deficit irrigation conditions. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Bartoszuk, W. 1987. Decrease in potato yield resulting from water deficit during the growing season. Potato Abstracts 15, Abst. No. 194.

Bastug, R. 1987. A study on determining the water production function of cotton under Cukuorova conditions (Ph.D. Thesis, Turkish). Adana, Turkey, Cukurova University, Faculty of Agriculture.

Bazza, M. 1999. Improving irrigation management. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Bazza, M. &Tayaa, M. 1999. Contribution to improve sugar beet deficit-irrigation. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Calvache, M. & Reichardt, K. 1999. Effects of water stress imposed at different plant growth stages of common bean (Pahaseolus vulgaris) on yield and N₂ fixation. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Craciun, L. & Craciun, M. 1999. Water and nitrogen use efficiency under limited water supply for maize to increase land productivity. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Day, A.D. & Intalap, S. 1970. Some effects of soil moisture stress on the growth of wheat. Agronomy Journal, 62: 27-29.

Eck, H.V., Mathers, A.C. & Musick, J.T. 1987. Plant water stress at various growth stages and growth and yield of soybean. Field Crops Research, 17: 1-16.

English, M.J., Musick, J.T. and Murty, V.V. 1990. Deficit irrigation. In: G.J. Hoffman, T.A. Towell & K.H. Solomon, eds. Management of farm irrigation systems, St. Joseph, Michigan, United States of America, ASAE.

FAO. 1979. Yield response to water by J. Doorenbos & A.H. Kassam. Irrigation and Drainage Paper No. 33. FAO, Rome.

Grimes, D.W. & Dickens, W.L. 1977. Cotton response to irrigation. California Agriculture 31, No. 5. Berkeley, California, United States of America, University of California.

Grimes, D.W. & Yamada, Y.H. 1982. Relation of cotton growth and yield to minimum leaf water potential. Crop Science 22: 134-139.

Iqbal, M.M., Shah, S.M., Mohammad, W. & Nawaz, H. 1999. Field response of potato subjected to water stress at different growth stages. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Jana, P.K., Misra, B. & Kar, P.K. 1982. Effects of irrigation at different physiological stages of growth on yield attributes, yield, consumptive use, and water use efficiency of sunflower. Indian Agriculturist 26: 39-42.

Karaata, H. 1991. Kirklareli kosullarinda aycicegi bitkisinin su-üretim fonksiyonlari. Köy Hizmetleri Arastirma Enst. Kirklareli, Turkey (Turkish), Report No 24 (PhD Thesis).

Kirda, C. & Kanber, R. 1999. Water, no longer a plentiful resource, should be used sparingly in irrigated agriculture. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Kirda, C, Kanber, R. & Tulucu, K. 1999a.Yield response of cotton, maize, soybean, sugar beet, sunflower and wheat to deficit irrigation. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Kirda, C., Moutonnet, P., Hera, C. & Nielsen, D.R (eds.). 1999b. Crop yield response to deficit irrigation. Dordrecht, The Netherlands, Kluwer Academic Publishers.

Korte, L. L., Williams, J.H. & Sorencen, R.C. 1983. Irrigation of soybean genotypes during reproductive ontogeny. I. Agronomic responses. Crop Science 23: 521-527.

Kovacs, T., Kovacs, G. & Szito, J. 1999. Crop yield response to deficit irrigation imposed at different plant growth stages. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Madanoglu, K. 1997. Water consumption of wheat (Yektay 406) in central Anatolia. Publication No. 52. Ankara. Ankara Central TOPRAKSU Research Institute. p. 67.

Minhas, J.S. & Bansal, K.C. 1991. Tuber yield in relation to water stress at stages of growth in potato (Solanum tuberosum L.). Journal of the Indian Potato Association 18: 1-8.

Musick, J.I. & Dusck, D.A. 1980. Planting date and water deficit effects on development and yield of irrigated winter wheat. Agronomy Journal, 72: 45-52.

Okman, C. 1973. Ankara Sartlarinda Seker Pancarinin su Istihlakinin Tayini Üzerinde bir Arastirma (Ph.D. Thesis). Ankara, Ankara University Publications.

Oylukan, S. 1973. Cesitli mahsüllerde ekonomik sulama sayisinin tesbiti denemesi sonuc raporu. Eskisehir Bölge TOPRAKSU Arastirma Enst. Md. 71, Eskisehir, Turkey.

Pene, C.B.G. & Edi, G.K. 1999. Sugarcane yield response to deficit irrigation at two growth stages. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Prieto, D. & Angueira, C. 1999. Water stress effect on different growing stages for cotton and its influence on yield reduction. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Rawson, H.M. & Turner, N.C. 1983. Irrigation timing and relationship between leaf area and yield in sunflower. Irrigation Science 4: 167-175.

Speck, J.E., Elmore, R.W., Eisenhauer, D.E. & Klocke, N.W. 1989. Growth stage scheduling criteria for sprinkler-irrigated soybeans. Irrigation Science 10: 99-111.

Stegman, E. C. 1982. Corn grain yield as influenced by timing of evapotranspiration. Irrigation Science 3: 75-87.

Stegman, E.C., Musick, J.T. & Stewart, J.I. 1980. Irrigation water management. In: M.E. Jensen ed. Design and operation of farm irrigation systems. St. Joseph, Michigan, United States of America, ASAE.

Stegman, E.C., Schatz, B.G. & Gardner, J.C. 1990. Yield sensitivities of short season soybeans to irrigation management. Irrigation Science 11: 111-119.

Stewart, J.I., Cuenca, R.H., Pruitt, W.O., Hagan, R.M. & Tosso, J. 1977. Determination and utilization of water production functions for principal california crops. W-67 California Contributing Project Report. Davis, United States of America, University of California.

Stewart, B.A. & Musick, J.T. 1982. Conjunctive use of irrigation and rainfall in semi-arid regions. Advances in Agronomy 1: 1-23.

Thomas, J.C., Brown, K.W. & Jordan, J.R. 1976. Stomatal response to leaf water potential as affected by preconditioning water stress in the field. Agronomy Journal 68: 706-708.

Trebejo, I. & Midmore, D.J. 1990.Effects of water stress on potato growth, yield and water use in a hot and cool tropical climate. Journal of Agricultural Science 114: 321-334

Waheed, R.A., Naqvi, H.H., Tahir, G.R. & Naqvi, S.H.M. 1999. Some studies on pre-planned controlled soil moisture irrigation scheduling of field crops. In: C. Kirda, P. Moutonnet, C. Hera & D.R. Nielsen, eds. Crop yield response to deficit irrigation, Dordrecht, The Netherlands, Kluwer Academic Publishers.

Winter, S.R. 1980. Suitability of sugar beets for limited irrigation in semi-arid climate. Agronomy Journal 72: 649-653.

Yavuz, M.Y. 1993. Farkli Sulama Yontemlerinin Pamukta Verim ve su Kullanimina Etkileri (Ph.D. Thesis). Adana, Turkey, Cukurova University, Faculty of Agriculture.

Ziska, L.H. & Hall, A.E. 1983. Seed yields and water use of cowpeas (Vigna unguiculata L. Walp.) subjected to planned water deficit irrigation. Irrigation Science 3: 237-245.