Drought stress, during growth season along with plant density, is an important problem that needs attention. In order to investigate the influence of both factors in increasing the water use efficiency, field experiments were laid out in split-plot design at Agriculture Research Station, Collage of Food and Agriculture Sciences, King Saud University, to investigate the effects of irrigation intervals viz., irrigation every (6, 9 and 12 days) under different plant densities i.e., (6, 8 and 10 plants/m 2) on growth, yield and yield component parameters as well as grain quality of sorghum local variety (Gizani). Results revealed that almost all growth, yield and yield component parameters were significantly influenced by both factors as well as their interaction. Chemical composition of seeds, leaf proline content and WUE were also considered. Severe drought stress condition caused gradual decrease in most of the growth characters as compared to watered treatment and reflected in decreasing yield and yield component characters. Increasing plant densities led to raise biomass production and seed yield per unit area and not able to compensated the low number and weight of grains per panicle. Contrary, low plant density, under adequate irrigation conditions, can be compensated by a high number of grains per panicle and high weight of the grain. Maximum seed yield per hectare was recorded by the interactional effects of most watered treatments (irrigation every 6 days) and plant density of 10 plants per square meter.
Human demand for food increases with increasing world population. It is expected that human population will increase to over 8 billion by the year 2020 and this will worsen the current scenario of food security. It is predicted that at least 10 million people will be hungry and malnourished in the world by the end of this century [
The picture is more aggravate under arid and semiarid regions, with the fact that over a quarter of land area on the earth is considered as arid and semiarid regions [
Plant density is the second important factor in crop yield. The use of proper planting density of sorghum crop plays an important role in the efficient use of water irrigation applied and reaches to optimum yield performance. The relationship between plant density and yield of cereals has been studied extensively, but conflicting reports have led to a renewed interest in the effects of high plant densities on yield of cereals. [
Factorial experiments based on split-plot design with four replications were done in two successive summer seasons of 2011 and 2012 to evaluate growth, yield and yield components parameters of local sorghum variety (Gizani) under three irrigation intervals viz., every (6, 9 and 12 days) were assigned in main plots and three plant densities i.e., (6, 8 and 10 plants/m2 achieve by plants spaced 30, 25 and 20 cm) were randomly distributed in sub-plots at Agriculture Research Station, Collage of Food and Agriculture Sciences, King Saud University, Deerab, South Riyadh region, Saudi Arabia (24.42˚N latitude and 46.44˚E longitudes, Altitude 600 m). The region is under arid climate conditions, with high temperatures and truncated rainfall during the summer and low temperatures and little rainfall during the winter season. Maximum and minimum mean temperature and relative humidity during the two growing seasons are presented in (
Prior to the field experiment, the field soil site was sampled 0 - 60 cm depth from five sites for physical and chemical analyses according to the methods described by [
Seed bed was prepared before sowing as recommended; field was ploughed three cross harrowing’s with tractor followed by a thorough harrowing to break the clods. Phosphorus fertilizer was applied at the rate of 70 kg. P2O5/ha. as the form of superphosphate (16% P2O5), whereas potassium as the form of potassium sulphate (42% K2O), by the rate of 100 kg K2O was applied broadcasting during soil preparation, the field was properly leveled
Month | Temperature (˚C) | Relative humidity (%) | ||||||
---|---|---|---|---|---|---|---|---|
Maximum | Minimum | Mean | ||||||
2011 | 2012 | 2011 | 2012 | 2011 | 2012 | 2011 | 2012 | |
May | 40.2 | 41.5 | 22.9 | 23.4 | 31.6 | 32.5 | 10.6 | 10.4 |
June | 42.7 | 44.4 | 24.8 | 25.9 | 33.8 | 35.2 | 10.2 | 10.3 |
July | 44.9 | 45.7 | 26.7 | 27.3 | 35.8 | 36.5 | 12.7 | 10.4 |
August | 44.9 | 45.9 | 27.8 | 26.9 | 36.4 | 36.4 | 10.9 | 10.8 |
September | 41.8 | 42.7 | 24.4 | 23.3 | 33.1 | 33.3 | 11.2 | 11.4 |
October | 37.2 | 38.2 | 19.4 | 18.5 | 28.3 | 33.3 | 11.3 | 11.6 |
Properties season | Saturation % | pH soil paste (1:5) | EC (dS/m) | O.M % | CaCO3 % | Field capacity (%) | Wilting point (%) | Sand (%) | Silt (%) | Clay (%) | Soil texture (%) |
---|---|---|---|---|---|---|---|---|---|---|---|
First season | 29.70 | 7.86 | 3.88 | 0.46 | 29.42 | 16.30 | 7.67 | 57.92 | 27.20 | 14.88 | Sandy loam |
Second season | 28.12 | 7.81 | 3.91 | 0.47 | 29.63 | 16.42 | 7.71 | 57.82 | 27.25 | 14.90 | Sandy loam |
Properties season | Available macro and micro nutrients (ppm) | ||||||
---|---|---|---|---|---|---|---|
N | P | K | Fe | Mn | Zn | Cu | |
First season | 35.40 | 14.80 | 243.50 | 3.27 | 2.44 | 6.07 | 0.70 |
Second season | 35.80 | 12.76 | 251.42 | 3.24 | 2.61 | 6.13 | 0.74 |
Properties season | pH | EC (dS/m) | O.M % | Soluble cations (meq./L) | Soluble anions (meq/L) | Total NPK (ppm) | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Ca+ | Mg+ | Na+ | K+ | Cl− | N | P | K | ||||||
First season | 7.10 | 1.45 | 0.02 | 6.30 | 1.75 | 7.35 | 0.44 | 2.40 | 4.85 | 9.14 | 10.50 | 9.23 | 17.00 |
Second season | 7.17 | 1.73 | 0.02 | 5.50 | 1.87 | 7.65 | 0.46 | 2.60 | 4.80 | 8.56 | 11.01 | 9.42 | 17.12 |
Water regime treatments | Mean water apply (m3/ha) | Number of irrigations over growing season | ||
---|---|---|---|---|
First season | Second season | First season | Second season | |
Weekly irrigation | 10,000 | 10,050 | 20 | 21 |
Irrigation every 9 days | 7000 | 7000 | 14 | 14 |
Irrigation every 12 days | 5000 | 5000 | 10 | 10 |
and divided into plots each one (3 × 3.5 m) included six ridges, three meters long and 50 cm apart, total experimental unit area was 10.5 m2 earmarked with raised bunds all around to minimize the movement of water. Pipe type was laid to facilitate irrigation to plots individually (irrigation network).Sowing was done on 14th and 16th April in the first and second seasons, respectively. Plants were thinned according to plant densities 20 days after sowing. Nitrogen fertilizer was applied by the recommended dose of N (100 Kg N/ha.) two times, once after thinning and the second 45 days later. Water irrigation applied according to the experimental treatments by using flowed irrigation system, through line pipe provide with meter gages for measuring water applied over the growing season.
Nine treatments were investigated in the study in a split-plot design arrangement in randomized complete block design with irrigation treatments (every 6, 9 and 12 days) as the main plot, and plant density (6, 8 and 10 plants/m2) as the sub-plot in three replications.
During growth stages number of days to 50% of flowering was determined. After 80 days from sowing a plant sample of 10 plants was taken for studying some growth parameters viz., plant height (cm), stem diameter (cm), number of green leaves per plant and leaf area (cm2) of the second upper leaf using the following formula: Leaf area (cm2) = leaf length (cm) × maximum leaf width (cm) × 0.747.
At harvest, two central rows of each sub-plot were hand pulled and completely air dried and threshed, then seed yield per hectare as well as biological yield per hectare were determined. Sub sample of ten plants was taken for determining yield component characters viz., head Length, cm; head weight, gm; grain weight per head gm; total plant weight kg, 1000 seed and grain yield per unit area.
1) Irrigation water-use efficiency
Irrigation water use efficiency (IWUE) kg/m3 is defined as the ratio of the crop yield (final economic yield) to irrigation water applied over the growing season, including rainfall [
2) Harvest and crop index
Harvest index (HI) and crop index (CI) were also calculated using the formula suggested by [
HI = Grain yield (kg∙ha−1)/Biological yield (kg∙ha−1) × 100.
Biological yield = Grain yield + straw yield, CI = Grain yield (kg∙ha−1)/Straw yield (kg∙ha−1) × 100.
1) Proline content
Leaf proline content was determined in fully expanded uppermost leaves at full flowering stage using the method of [
2) Chemical composition of grains
Crude Protein content was estimated by determining nitrogen content in absolutely dry seeds using micro- kjeldahl method according to the procedures described by [
Total carbohydrates percentage were determined using spectrophotometer and total soluble sugar using soxhelt apparatus by the method described by [
The experimental design was laid out in split-plot design with 4 replications according to the methods described by [
Analysis of variance of the data for growth characters presented in (
The data presented in the same table also evident that increasing plant competition for water and nutrients, which are induced at high plant densities, resulted in decreased the time required to reach to 50% of flowering, plant height, stem diameter, number of green per plant, and leaf area in both seasons. Similar results were obtained by [
Irrigation intervals (A) | Plant density, m2 (B) | 2011 season | 2012 season | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
50% Flowering | Plant height cm | Stem diameter, cm | No. of leaves/ plant | Leaf area cm2 | 50% flowering | Plant height cm | Stem diameter cm | No. of leaves/ plant | Leaf area cm2 | |||
6 | 6 | 77.0 | 269.5 | 1.4 | 9.7 | 591.7 | 79.0 | 276.5 | 1.4 | 10.0 | 615.4 | |
8 | 74.0 | 255.5 | 1.4 | 9.8 | 582.5 | 76.0 | 261.0 | 1.3 | 9.9 | 584.5 | ||
10 | 72.0 | 237.9 | 1.2 | 8.8 | 563.4 | 73.0 | 243.5 | 1.3 | 8.6 | 584.2 | ||
General mean | 74.3 | 254.3 | 1.3 | 9.4 | 579.2 | 76.0 | 260.3 | 9.5 | 594.7 | |||
9 | 6 | 73.0 | 230.7 | 1.2 | 8.7 | 553.3 | 73.0 | 236.5 | 1.1 | 8.8 | 578.2 | |
8 | 72.0 | 222.5 | 1.1 | 8.6 | 546.8 | 73.0 | 225.0 | 1.0 | 8.9 | 554.6 | ||
10 | 70.0 | 218.8 | 1.0 | 8.8 | 537.4 | 68.0 | 219.7 | 1.1 | 8.9 | 536.2 | ||
General mean | 71.7 | 224.0 | 1.1 | 8.7 | 545.8 | 71.3 | 227.0 | 8.9 | 556.3 | |||
12 | 6 | 70.0 | 226.5 | 1.0 | 8.0 | 542.6 | 70.0 | 223.6 | 0.9 | 7.9 | 534.8 | |
8 | 72.0 | 215.8 | 1.0 | 7.8 | 522.7 | 73.0 | 220.5 | 0.9 | 7.8 | 522.7 | ||
10 | 68.0 | 207.5 | 0.9 | 7.7 | 498.6 | 68.0 | 210.4 | 0.9 | 7.6 | 492.7 | ||
General mean | 70.0 | 216.6 | 0.97 | 7.8 | 521.3 | 70.3 | 218.2 | 7.8 | 516.7 | |||
General mean of factor (B) | 6 | 73.3 | 242.2 | 1.2 | 8.8 | 562.5 | 74.0 | 252.8 | 1.1 | 8.9 | 576.1 | |
8 | 72.7 | 231.3 | 1.2 | 8.7 | 550.7 | 74.0 | 235.5 | 1.1 | 8.9 | 553.9 | ||
10 | 70.0 | 221.4 | 1.0 | 8.4 | 533.1 | 69.7 | 224.5 | 1.1 | 8.4 | 537.7 | ||
LSD | A | 1.4 | 10.16 | ns | 1.2 | 28.4 | 1.0 | 12.4 | ns | 0.82 | 30.7 | |
B | 0.5 | 6.9 | ns | ns | 10.9 | 2.3 | 9.2 | ns | ns | 14.9 | ||
A × B | 1.2 | 5.7 | ns | 1.0 | 4.0 | 1.8 | 7.6 | ns | 0.74 | 18.4 | ||
decreasing plant growth with increasing plant densities was also observed by [
Yield component characters is a complex trait affected by many factors i.e., nutrients absorption; photosynthesis; management agronomic practices and the mutual effects of genetic constituencies in various environments [
Plant density in this study was categorized in class b (
A general and gradual decrease in grain yield production, biological yield, harvest index and crop index was observed as the time of applied irrigation water in the three sorghum plant densities increased. Thus, the maximum values of all of these parameters were obtained in the most watered treatments, generally in treatment irrigated every 6 days and the minimum values in the less irrigated treatments, which irrigation was located every 9 and 12 days in the same sorghum densities (
Irrigation intervals | Plant density M2 | 2011 season | 2012 Season | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Panicle length cm | Panicle weight gm | Grain weight/ panicle gm | 1000 grain weight gm | No. Of grains per panicle | W U E Kg/M3/Ha | Panicle length cm | Panicle weight gm | Grain weight/ panicle, gm | 1000 Grain weight, gm | No. Of Grains per panicle | WUE Kg/M3/Ha | |||
6 | 6 | 22.2 | 120.9 | 103.7 | 35.5 | 310.4 | 0.336 | 23.3 | 117.9 | 109.3 | 36.7 | 305.4 | 0.356 | |
8 | 20.3 | 102.8 | 80.6 | 33.2 | 240.9 | 0.344 | 20.8 | 91.1 | 93.6 | 34.8 | 250.8 | 0.365 | ||
10 | 18.9 | 87.9 | 66.7 | 31.5 | 204.7 | 0.391 | 18.7 | 88.9 | 67.5 | 33.2 | 200.5 | 0.378 | ||
General mean | 20.47 | 103.87 | 83.67 | 33.40 | 252.0 | 0.357 | 20.93 | 99.3 | 90.13 | 34.9 | 252.23 | 0.366 | ||
9 | 6 | 20.0 | 89.8 | 68.5 | 33.4 | 209.8 | 0.437 | 20.3 | 91.8 | 78.8 | 34.5 | 222.4 | 0.451 | |
8 | 17.8 | 92.4 | 65.4 | 31.2 | 200.7 | 0.449 | 18.2 | 96.1 | 74.7 | 32.4 | 210.9 | 0.463 | ||
10 | 17.0 | 82.7 | 61.5 | 30.1 | 200.0 | 0.471 | 17.5 | 86.4 | 64.5 | 31.7 | 204.0 | 0.477 | ||
General mean | 18.27 | 88.30 | 65.13 | 31.57 | 203.5 | 0.452 | 18.67 | 91.43 | 72.67 | 32.87 | 212.43 | 0.464 | ||
12 | 6 | 18.7 | 86.5 | 59.3 | 30.2 | 190.8 | 0.520 | 17.9 | 87.6 | 55.4 | 31.4 | 177.0 | 0.544 | |
8 | 18.0 | 82.4 | 56.2 | 29.4 | 191.6 | 0.520 | 17.2 | 84.3 | 58.7 | 30.2 | 190.8 | 0.568 | ||
10 | 17.2 | 76.8 | 54.6 | 28.5 | 188.7 | 0.568 | 17.0 | 80.7 | 56.5 | 30.3 | 180.6 | 0.588 | ||
General mean | 17.97 | 81.90 | 56.70 | 29.37 | 190.37 | 0.536 | 17.37 | 84.2 | 56.87 | 30.63 | 182.80 | 0.567 | ||
General mean of factor (B) | 6 | 20.3 | 99.07 | 77.17 | 33.03 | 237.0 | 0.431 | 20.5 | 99.10 | 81.17 | 34.20 | 234.93 | 0.450 | |
8 | 18.7 | 92.53 | 67.40 | 31.27 | 211.1 | 0.438 | 18.7 | 90.58 | 75.67 | 32.47 | 217.50 | 0.465 | ||
10 | 17.7 | 82.47 | 60.93 | 30.03 | 197.8 | 0.477 | 17.7 | 85.33 | 62.83 | 31.73 | 195.03 | 0.481 | ||
LSD | A | 1.0 | 4.8 | 8.3 | 1.3 | 18.2 | --- | 1.1 | 5.2 | 14.2 | 1.8 | 20.4 | --- | |
B | 0.82 | 6.2 | 5.4 | 0.94 | 10.3 | --- | 0.89 | 3.6 | 11.6 | 0.66 | 14.8 | --- | ||
A × B | 0.94 | 7.5 | 1.8 | 1.2 | 12.4 | ---- | 0.70 | 4.2 | 8.5 | 1.2 | 10.7 | --- | ||
Irrigation intervals | Plant density m2 | 2011 season | 2012 season | |||||||
---|---|---|---|---|---|---|---|---|---|---|
Grain yield (g/m2) | Biological yield (g/m2) | HI % | CI % | Grain yield, (g/m2) | Biological yield (g/m2) | HI % | CI % | |||
6 | 6 | 336 | 1132.3 | 0.30 | 0.42 | 356 | 1166.4 | 0.30 | 0.44 | |
8 | 344 | 1143.9 | 0.30 | 0.43 | 364 | 1210.5 | 0.30 | 0.43 | ||
10 | 391 | 1338.0 | 0.29 | 0.41 | 378 | 1293.0 | 0.29 | 0.41 | ||
General mean | 357.0 | 1204.7 | 0.30 | 0.42 | 366.0 | 1223.3 | 0.30 | 0.43 | ||
9 | 6 | 306 | 891.6 | 0.52 | 0.52 | 316 | 899.2 | 0.45 | 0.54 | |
8 | 314 | 800.0 | 0.39 | 0.65 | 324 | 857.4 | 0.38 | 0.61 | ||
10 | 330.0 | 905.5 | 0.36 | 0.57 | 334 | 976.5 | 0.34 | 0.52 | ||
General mean | 316.7 | 865.7 | 0.40 | 0.58 | 324.7 | 844.4 | 0.39 | 0.56 | ||
12 | 6 | 260 | 504.3 | 0.51 | 1.06 | 272 | 577.3 | 0.47 | 0.89 | |
8 | 260 | 514.9 | 0.51 | 1.02 | 284 | 566.9 | 0.50 | 1.00 | ||
10 | 284 | 624.4 | 0.45 | 0.83 | 274 | 603.4 | 0.45 | 0.83 | ||
General mean | 268.0 | 547.9 | 0.49 | 0.96 | 283.3 | 582.5 | 0.47 | 0.91 | ||
General mean of factor (B) | 6 | 300.7 | 769.4 | 0.42 | 0.64 | 314.7 | 814.3 | 0.41 | 0.62 | |
8 | 306.0 | 819.6 | 0.40 | 0.60 | 324.0 | 878.3 | 0.39 | 0.68 | ||
10 | 335.0 | 956.0 | 0.37 | 0.54 | 335.3 | 957.6 | 0.36 | 0.59 | ||
LSD | A | 22.4 | 45.20 | --- | --- | 32.8 | 87.9 | --- | --- | |
B | 18.3 | 40.89 | --- | --- | 8.7 | 42.8 | --- | --- | ||
A × B | 21.0 | 12.60 | --- | --- | 9.6 | 62.4 | --- | --- | ||
final yield and yield component characters of sorghum were investigated by some researchers, they concluded that, identification the optimum time of water supplies can reach to the optimal yield performance. Compatible results were obtained by [
Proline content reduced under moderate water stress, but increased under severe water stress (
Irrigation intervals | Plant density m2 | 2011 season | 2012 season | |||||
---|---|---|---|---|---|---|---|---|
Leaves proline content (μmol/g FW) | Crude protein % | Total carbohydrate % | Leaves proline content (μmol/g FW) | Crude protein % | Total carbohydrate % | |||
6 | 6 | 2.38 | 10.26 | 84.55 | 2.72 | 12.46 | 82.65 | |
8 | 2.78 | 9.12 | 83.52 | 2.82 | 10.25 | 82.12 | ||
10 | 3.00 | 8.22 | 83.22 | 2.89 | 9.72 | 81.42 | ||
General mean | 2.72 | 9.20 | 83.76 | 2.81 | 10.81 | 82.06 | ||
9 | 6 | 3.10 | 9.82 | 83.00 | 3.57 | 10.22 | 81.21 | |
8 | 3.24 | 8.62 | 82.69 | 3.30 | 9..32 | 81.00 | ||
10 | 3.28 | 8.10 | 82.42 | 3.34 | 8.00 | 80.45 | ||
General mean | 3.21 | 8.85 | 82.70 | 3.40 | 9.18 | 80.89 | ||
12 | 6 | 3.00 | 8.24 | 82.32 | 3.38 | 9.44 | 80.12 | |
8 | 3.33 | 7.65 | 82.00 | 3.42 | 8.12 | 80.00 | ||
10 | 3.52 | 7.23 | 82.00 | 3.86 | 8.00 | 80.00 | ||
General mean | 3.28 | 7.71 | 82.11 | 3.55 | 8.52 | 80.04 | ||
General mean of factor (B) | 6 | 2.83 | 9.44 | 83.29 | 3.22 | 10.71 | 81.33 | |
8 | 3.12 | 8.46 | 82.74 | 3.18 | 9.23 | 81.04 | ||
10 | 3.27 | 7.85 | 82.55 | 3.36 | 8.57 | 80.62 | ||
LSD | A | 0.36 | ---- | ---- | 0.54 | ---- | ---- | |
B | 0.28 | ---- | ---- | 0.12 | ---- | ---- | ||
A × B | 0.21 | ---- | ---- | 0.34 | ---- | ---- | ||
moisture content in root zone recorded the highest values of leaf proline content. Such effect may be attributed to high competition between plants for water and dissolving nutrients and low photosynthetic substrates translocation. From the data in the same (
The effect of different plant densities on leaves proline content and grains chemical composition, data obtained reveal that increasing number of plants per square meter decreased either leaves proline content or grains chemical composition, whereas carbohydrate content did not gave a stable or defined trend on both seasons. The interaction effect in (
Decreasing water supply by increasing the time between irrigations produced a significant reduction of the aerial sorghum characters viz., stem diameter, number of green leaves per plant, time required to reach to 50% flowering, plant height, leaf area per plant and all of these parameters put in a reduction in the grain yield. The most important parameter among yield component parameters under investigation is harvest index, which is increased as water stress increased. Such results indicated that grain yield was more sensitive to water stress than the aerial dry matter production. For the three plant densities, the relationship between grain yield and harvest index was similar under the three water irrigation applied.
The results indicated that important compensation processes occurred between the different sorghum yields components. Thus, the lesser number of plants per m2 of the lower sorghum densities were compensated with a greater production of tillers, a greater number of grains per panicle and a higher weight of these grains. The result of this study suggests that sowing sorghum using less density could be an alternative crop if water supply is limiting under water deficit conditions.
The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for financially supporting this work.
Ali A.Alderfasi,Mostafa M.Selim,Bushra A.Alhammad, (2016) Evaluation of Plant Densities and Various Irrigation Regimes of Sorghum (Sorghum bicolor L.) under Low Water Supply. Journal of Water Resource and Protection,08,1-11. doi: 10.4236/jwarp.2016.81001