Evaluation of dryland crop management innovations for subsistence farmers of pearl millet (Pennisetum americanum (L.) K. Schum.) in Niger

Eur. J. Agron., 1993, 2(1), 39-50

Evaluation of dryland crop management innovations for subsistence farmers of pearl millet (Pennisetum americanum (L.) K. Schum.) in Niger N. Persaud* (1), F. G. Calhoun (2), M. Gandah (3), M. Ouattara (3) and N. Mokete (4) (I) Dept. Crop and Soil Environment Sciences, Virginia Polytechnic Institute and State Univ, Blacksburg, Virginia 24061-0404, U.S.A. (2) Agronomy Dept., Ohio State Univ., Columbus, Ohio 43210, U.S.A. lnstitut National de Recherches Agronomiques du Niger, B.P. 429, Niamey, Niger. 4 ( ) Dept. of Agricultural Research, Pvt. Bag 0033, Gaborone, Botswana.

e)

Accepted 15 February 1993. (*) To whom correspondence should be addressed.

Abstract

Field experiments were conducted at several locations in Niger between February 1985 and September 1987. Three experiments were designed to evaluate if removal of tillers in conjunction with other crop management practices would improve the growth, productivity, and water use efficiency of pearl millet. A fourth was designed to evaluate if intercropping of long-, medium-, and short-season cultivars of pearl millet would result in better crop yields. The combined results for the first three experiments showed that tiller removal did not have a beneficial effect on growth and productivity of pearl millet. About 25 per cent of the tillers could be safely removed at growth stage 4 (as defined by Maiti and Bidinger, 1981) without affecting yields, especially for the locally grown cultivars. The results of the fourth experiment showed that 50 : 50 combinations of either of the two improved shorter season cultivars, HKP and CIVT, with the local long-season cultivars gave lower yields than the improved cultivars grown in pure stands. However, yields from these 50 : 50 combinations were higher than those of the local cultivar grown alone. A 1 : 1 : 1 combination of all three cultivars in lines or in the same hill yielded the same as the improved cultivars grown singly but gave markedly greater yields (p < 0.05) than the local cultivars grown in pure stands. However, more studies over several seasons are required to make firm conclusions on the potential of this practice. Both sets of experiments clearly showed that the improved cultivars, HKP and CIVT, were superior to the locally grown cultivars. Fertilizer P and N also benefited yields but their application may not be feasible for resourcepoor subsistence farmers. Key-words : dryland, crop management, pearl, millet, Niger.

INTRODUCTION Pearl millet [Pennisetum americanum (L.) K. Schum.] is the staple cereal in Niger. South of 14150 north latitude, the monsoon rainfall from June through September in Niger is adequate to sustain dryland production of pearl millet by subsistence

farmers. The farmers' traditional dryland crop management practices for millet evolved as risk-aversion strategies based on their collective semi-empirical perceptions of the irregularity and unreliability of the monsoon rainfall (Ouattara and Persaud, 1985 ; Persaud et al., 1986). Persistent failure of the monsoon rains between

1968 through 1974 over most of the West African Contribution no. 91-557-J of the Kansas Agric. Exp. Stn. Research partially funded by the United States Agency for International Development through the Niger Agricultural Sector Development Grant, through Grant No. DAN 1254-G-SS-5065-00 and through Grant No. DAN 1311-G-SS6018-00. * Corresponding author. ISSN 116J.0301/93/0l/39 12 $ 3.20/ © Gauthier-Villars - ESAg

semi-arid tropics resulted in a major effort to introduce dryland farming innovations that might mitigate the effects of intra-seasonal drought and crop stress. For example, considerable progress has been made in developing cultivars of pearl millet with shorter growing periods than the traditional cultivars, in order to

40

escape periods of less reliable rainfall. Less progress has been made in designing crop management practices that will alleviate the impact of drought and at the same time be socio-economically viable and sustainable for subsistence farmers. The objective of this study was to evaluate two such practices based on artificial manipulation of the amount, type, and spatial distribution of the crop biomass. The first of these management practices was tiller removal. High tillering crops such as wheat, rice and barley produce many more tillers than actually produce grain. Yoshida (1972) suggests that tillers may play a beneficial role in adverse environmental conditions. Single plants of local cultivars of millet in Niger can produce 18 to 25 tillers. About 30-40 per cent of these tillers produce heads. It seems that traditional pearl millet cultivars in Niger have been selected for high tillering capacity. Tillers seem to play an important role in the growth, development, and yield of millet in Niger. From a drought escape viewpoint, tillers transpire water and, if not productive, reduce the water use efficiency of the plant. On the other hand, tillers increase the available surface for photosynthesis and, therefore, dry matter production. Mahalakshmi and Bidinger (1985) investigated the flowering response of main shoots and tillers of pearl millet cultivars when stressed during panicle development. Severe water deficit during this period delayed flowering in early genotypes. Delay in flowering was more pronounced in tillers than in main shoots but the proportion of tillers producing an inflorescence was increased by water stress. Grain yield losses from the main shoots were compensated by the increase in yield from the tillers. Thus the delay in flowering and the buffering by the tillers provided an adaptive mechanism that overcame the period of stress prior to flowering. In late genotypes, panicle initiation in tillers occurred only after release of the stress. In continued studies, Bidinger et al. (1987) found that tillers compensated the grain yield of pearl millet cultivars when drought stressed at midseason i.e. between panicle initiation and flowering. The yield response of the genotypes to midseason stress was related to their phenology, especially to the time to flowering. Azam-Ali et al. (1984) studied the growth and development and water use of pearl millet grown on stored water at row spacings of 38, 75, and 150 em. Initially, shoot growth was fastest at the narrow spacings, but eventually the wide row spacing produced most dry matter, mainly due to greater survival of the tillers. The partitioning of the above ground dry matter into stover and grain was similar at all three spacings. Dry weight increased in proportion to intercepted radiation regardless of spacing. Tillers apparently played an important role in the development and maintainance of the crop canopy. Stored water was used more efficiently in the wider spacing.

N. Persaud et al.

Traditionally the subsistence farmers of pearl millet in Niger sow many seeds per hill and thin each hill two to three weeks after emergence. It has been observed that the number of productive tillers decreases if the stand is thinned to more than one plant per hill. Unpublished data from a study at the experiment station at Tarna near Maradi in Niger (J. Gondah, personal communication) showed that approximately 3 to 4 times more productive tillers were obtained from stands thinned to one plant per hill than from traditional stands thinned to three plants per hill. This indicates that the local cultivars are phenotypically plastic and tend to self-adjust their biomass production. The study also indicated that the traditional thinning practice optimized the interrelationship between productive heads per hill and the number of main plants and their tillers in the hills. There are no previous reports on the effect of artificially reducing the biomass of millet stands by tiller removal on grain yields. Some data were available (M. Djika, personal communication) from a study of the removal of various leaves of sorghum plants at growth stage 6 as defined by Vanderlip (1987). The study was conducted at the experiment station at Bambey in Senegal during the 1976 growing season, and included six sorghum cultivars grown in plots arranged in completely randomised blocks with six replicates. At GS6, plants of each variety were treated as follows : control, no leaves removed, flag leaf removed, leaves 1 and 2 removed, leaves 3 and 4 removed, and leaves 5 and 6 removed. Our analysis of these data showed no interaction between the cultivars and these treatments and a marginally significant effect (P > F = 0.09) of these treatments on the mean head weight taken over all cultivars. Intercropping of pearl millet with other crops is a traditional practice in Niger. It is estimated that about 70 per cent of the millet grown is intercropped with cowpeas (C. Reddy, personal communication). Intercropping of millet with sorghum is also observed, often with both crops sown in the same hill. On sloping lands, a common management system is to grow millet on the upper part of the slope, a mixture of sorghum and millet on the middle portions, and sorghum or maize on lower, more level ground (Stoop, 1987). This practice is justified probably because the depth of the soil profile and soil moisture content increase progressively down the slope, and millet is considered the most drought tolerant, followed by sorghum and maize. The development of short-season cultivars of millet opens up the possibility of intercropping these with the traditional longer-season cultivars. The second practice evaluated in our study was intercropping of various combinations of short-, medium-, and long-season cultivars of pearl millet. Eur. J. Agron.

41

Management of dryland pearl millet in Niger

MATERIALS AND METHODS

3. No removal of tillers and removal by knife of 50 per cent of the tillers at GS4 and GS6.

During the period from February 1985 through September 1987, four field experiments denoted E1 to E4 were conducted at various locations in Niger. A synopsis of these experiments is given in Table 1. The latitudes and longitudes given in Table 1 for E1 to E4, respectively, are those for the meteorological stations in the nearby towns of Maradi, Brni N'Gaoure, Kolo, Gaya (Malgorou), and Say (Tyleda). The soils at all these sites were ferallic arenosols also termed sols dunaires or sols ferrugineux tropicaux. In the USDA system of soil taxonomy, they correspond to psammentic paleustalfs.

No rain falls in Niger during the winter and spring, so the crop was grown entirely under irrigation. The strips were irrigated by sprinklers ; one at a consistently lower level of water application than the other. This was done by varying the time of sprinkling the two strips. The amount of water applied was measured. To do this, a 3 m metal post was installed in each of 12 plots in each strip. Each post was randomly allocated to the middle or either end of the plot. Plastic cups 9 em in diameter were mounted on a removable arm bolted to each post. After each irrigation, the volume of water collected in these cups was measured. The average depth of irrigation was calculated from these measurements. The cups were raised progressively as the crop grew.

Experiment El In this experiment, plots of 10 m x 5 m were laid out in two parallel strips of 24 plots. The strips were separated by 20 m. The 24 plots in each strip were arranged in three blocks of eight plots. The treatments consisted of factorial combinations of the following : 1. Millet cultivars Zongo, a long-season cultivar, and Haini Kire Precoce (HKP), an improved shortseason cultivar. 2. No fertilizer and the recommended level of 22.5 kg ha- 1 P 20 5 as single superphosphate and 45 kg ha - 1 N as urea. The phosphate was applied broadcast before planting and worked into the soil with hoes. Half of the N was applied as a side dressing after thinning and the other half at GS4 as defined by Maiti and Bidinger (1981).

The plots were irrigated equally and then handplanted between 15 and 19 February, 1985. The inrow and between-row spacing was 1 m. The stand was thinned to three plants per hill 20 days after emergence. Before the initial irrigation, 12 plots in each strip were sampled for soil moisture. Samples were taken at 20 em depth intervals down to 200 em. Soil moisture contents of these samples were determined gravimetrically. Two holes were augered in each plot. For each depth interval, the soil from each hole was composited, and a single sample was taken for analysis. A similar sampling was done immediately after harvest. During the growth of the crop, a pit was dug in the field, and core samples were taken at 20 em intervals to determine the dry bulk density.

Table 1. - Synopsis of field experiments conducted between February 1985 and September 1987 to evaluate crop management practices for subsistence farmers in Niger. Experiment

Synopsis of treatments

Location and duration

Design

El

2 levels of tiller removal on two culti vars of millet at 2 levels of fertilizer evaluated at 2 levels of irrigation.

Experimental station at Tarna, Lat. 13 28 N., Long. 07 25 E., February to June 1985.

3 factor factorial in RCB at each irrigation level, with 3 replicates.

E2

Evaluation removal.

tiller

Experimental sub-station Kalapate, Lat. 13 28 N., Long. 02 54 E., July to Sept. 1985.

Completely 6 replicates.

E3

Evaluation of 4 levels of tiller removal, on 3 cultivars of millet, at 2 levels of fertilizer.

Centre de Formation des Jeunes Agriculteurs farm at N'Dounga, Lat. 13 18 N., Long. 02 21 E., July to Sept. 1986.

Complete factorial in RCB with 3 replicates. Total of 24 treatments.

E4

Evaluation of intercropping of a short-, medium-, and long-season millet cultivars in all combinations.

Research implemented and manfarmers' fields at aged on Malgorou, 11 59 N. Lat., 03 30 E. Long., and Tyeleda 13 06 N. Lat., 02 21 E. Long. June to Sept. 1987

RCB with 5 replicates. The treatment with all 3 cultivars was intercropped in rows and in the same hills, giving a total of 8 treatments.

Vol. 2,

0°

I - 1993

of

2 levels

of

randomised,

with

N. Persaud et al.

42

Three cores were taken from each depth interval. The gravimetric water contents of the soil samples taken in the experimental plots were multiplied by the measured mean dry bulk density of 1.57 g ml- 1 to convert to volumetric water content. Trapezoid rule integration was used to calculate a mean value of moisture storage in the 200 em depth of the soil profile. The tillers removed from the plots at GS4 for each irrigation level were sun-dried and weighed. Before elongation of the internodes at GS4, 10 main stems in each plot were tagged. The heights of these plants were measured on 1, 4, 9, 12, 15, 19, 23, and 30 April. The height was measured from the ground to the highest point when the leaves were pulled erect or to the top of the inflorescence when this became greater. At GS6, the total number of stems including tillers in four randomly selected pockets in each plot were counted. Harvest was taken from an area 3 m x 9 m consisting of 27 hills from each plot. At harvest, the total number of stems in the harvested hills was counted. The harvested heads were divided into mature fertile heads, infertile heads, and immature heads. The mature fertile heads harvested from each plot were spread out and sun-dried for several weeks. They were then bundled and weighed and left for threshing. Unfortunately, many of these bundles were attacked by termites before threshing, and the data collected on grain yield were discarded. Experiment E2

Originally, it was planned to repeat experiment El under rainfed conditions during the 1985 rainy season. This was not possible, and instead experiment E2 was conducted mainly to compensate for the loss of the grain yield data in experiment El and to study the effect of tiller removal under rainfed conditions. Plots were 9 m x 9 m. The tillers were removed only once at the end at GS4. Fertilizer P and N were applied to the experimental area as described for El. At harvest, similar data were collected as for E l. Experiment E3

This experiment was designed to study more closely the effects of tiller removal under rainfed conditions under different crop management systems. Plots 9 m x 8 m were laid out in three blocks of 24 plots each. Treatments consisted of factorial combinations of : 1. Three pearl millet cultivars, HKP, Composite Inter-Varietal du Tama (CIVT), and the locally grown cultivar obtained from farmers near the site at N'Dounga. 2. Two levels of fertilizer, 22.5 kg ha- 1 P 20 5 as single superphosphate combined with 45 kg ha- 1 N or with 65 kg ha- 1 N as urea. The fertilizers were applied as described for experiment El.

3. Four levels of tiller removal, none or removal of 25, 50, and 75 per cent of the tillers present at GS4. The removal was done in the same way as for E 1 and E2. Daily rainfall at the site was measured with two standard non-recording rain gauges. The crop was sown following planting rains between 3 July and 6 July 1986. After tiller removal, aluminium access tubes for a neutron probe were installed in each of the plots with the four tiller removal treatments. Thermal neutron count data were collected using a Troxler apparatus for determination of the soil volumetric water content. Water content in the 0-30 em depth interval was measured gravimetrically at 5-cm intervals. A measured dry bulk density of 1.5 gm ml- 1 was used to convert these measured gravimetric soil moisture contents to volumetric values. The neutron probe was used for measuring water contents between 30 and 270 em depths at 20 em intervals. Observations were made on 28 August and 3, 9, 13, and 20 September 1986. At harvest, yield data were collected as for experiments El and E2. Experiment E4

This experiment was designed to study the effects of intercropping of pearl millet cultivars at different locations along the north-south rainfall gradient in Niger. Three on-farm sites were selected at increasing north latitude. The crop at the northernmost site at Ouenditan along the Niamey-Filingue road failed and data were collected only for the intermediate site at Tyeleda and the southernmost site at Malgorou. Plots 9 m x 8 m were laid out in five blocks of eight plots each. The treatments consisted of intercropping of three pearl millet cultivars, HKP, CIVT, and the locally available cultivar in all seven possible combinations. The intercropped cultivars were sown in separate rows in the plots. In addition, the treatment combination of all three cultivars was also sown in the same hills, giving a total of eight treatments. The crop was sown between 4 and 6 June 1987 at Malgorou and between 20 and 22 June at Tyeleda. The cultivars were harvested at the same time in the intercropped plots. The harvest dates were 9 September at Malgorou and 25 September at Tyeleda. Yield data were collected as for the other experiments. After the heads were cut, the stover was harvested, and the fresh weights were recorded. RESULTS AND DISCUSSION Experiment El

The two levels of irrigation measured over the growth of the crop were 309 mm and 233 mm. These were designated as high and low levels, respectively. Eur. J. Agron.

Management of dryland pearl millet in Niger

43

Table 2. - Effect of cultivar, fertilizer, and tiller removal on yield of fertile mature sun-dried heads, mean head weight, total and fertile heads per hill, ratio of fertile to total heads per hill, and stems per hill at flowering and at harvest for pearl millet at the low irrigation level in experiment El at Tarna. Treatment or statistic

Heads kg ha· 1

Heads per hill

Stems per hill

Mean head weight (g)

Total

Fertile

Ratio%

GS6

harvest

Overall mean cv % SED 1

546.3 32.4 72.4

19.2 13.3 1.0

4.6 13.0 0.24

2.9 30.6 0.36

62.2 24.9 6.3

12.7 13.9 0.72

II. I

Cultivar Zongo HKP

424.4 668.2

21.5 16.8

3.6 5.5

1.9 3.9

52.8 71.6

*

**

13.4 12.0 ns

11.2 10.9 ns

2.5

65.2

11.5

10.0

3.3

59.3 ns

13.9

12.1

**

**

3.0

63.6

15.4

13.1

2.8

60.8 ns

**

* Fertilizer None Recommended rates of N, P Tiller removal None 50 % removed at GS4 and GS6

**

**

461.4

18.7

631.1

**

19.7 ns

572.5

19.8

4.6

520.1 ns

18.6 ns

4.6 ns

3.8 5.4

**

**

**

10.0

6.1 0.27

9.0

**

1 SED= The standard error of a mean difference for a given observation is the same for all 3 factors. Error df for comparison of means = 14. * ** denotes significant differences at P = 0.05 and 0.01 respectively ; ns = not significant. There were no two or three-way interactions.

Table 3. - Effect of cultivar, fertilizer, and tiller removal on yield of fertile mature sun-dried heads ; mean head weight ; total and fertile heads per hill ; ratio of fertile to total heads per hill ; and stems per hill at flowering and at harvest for pearl millet at the high irrigation level in experiment El at Tarna. Treatment or statistic Overall mean cv % SED 1 Cultivar Zongo HKP Fertilizer None Recommended rates of N, P Tiller removal None 50 % removed at GS4 and GS6

1

Heads kg ha· 1

Mean head weight (g)

Heads per hill

Total

Stems per hill

Fertile

Ratio %

GS6

harvest

800.4 45.8 149.5

24.0 39.4 3.9

6.3 11.6 0.30

3.6 20.5 0.29

54.4 22.4 5.0

13.7 20.2 1.1

12.1 9.3 0.46

525.2 1055.6

5.0 7.6

2.0 5.1

42.1 66.7

**

27.0 20.9 ns

**

**

**

14.0 13.4 ns

12.1 12.1 ns

666.7

22.5

5.3

3.2

58.7

12.2

11.3

934.1 ns

25.4 ns

7.4

4.0

**

50.1 ns

15.2

**

810.6

21.5

6.7

4.0

54.7

17.6

15.1

790.1 ns

26.4 ns

5.9

3.2

9.1

*

54.1 ns

9.8

*

**

**

SED = The standard error of a mean difference for a given observation is the same for all 3 factors. Error df for comparison of means = 14. *, ** denotes significant differences at P = 0.05 and 0.01 respectively; ns = not significant. Highly significant fertilizer x cultivar and cultivar x tiller removal interaction for fertile heads per hill. Highly significant fertilizer x cultivar interaction for stems per hill at GS6 and at harvest. Vol. 2, n° I - 1993

*

12.9

**

N. Persaud et al.

44

Table 4. - Interaction of fertilizer x cultivar on fertile heads per hill and stems per hill at GS6 and at harvest and for cultivar x tiller removal on fertile heads per hill for pearl millet at the high irrigation level in experiment EI at Tarna. Fertile heads per hill 1 SED = 0.42

Fertilizer None Recommended rate N, P Tiller removal None 50 % removal at GS3 & GS6 1

Zongo

HKP

Zongo

HKP

2.0 2.0

4.3 5.9

10.7 17.3

13.8 13.0

10.6 13.5

12.0 12.2

2.0 2.1

6.0 4.3

SED= standard error of a mean difference. Error df for comparison of means= 14.

The effect of the treatments on observations collected at harvest are presented in Tables 2 and 3 for the low and high irrigation levels, respectively. Comparison of these tables clearly shows that the crop grew and performed better at the higher irrigation level for all the treatments. More irrigation increased the overall mean yield per hectare of the mature, fertile, sun-dried, and unthreshed heads by 46 per cent over that at the low irrigation level. Although threshed grain yields were not available, an average threshing percentage of 70 can be used for purposes of comparison. Using this value, the overall grain yields were 382 kg ha- 1 and 560 kg ha- 1, respectively, for the low and high irrigation levels. The higher irrigation level also resulted in the overall production of more (p < 0.05) tillers and total heads. However, a greater percentage of heads was fertile and mature at the lower irrigation level.

A greater fraction of the heads produced by HKP was fertile and mature. Fertilizer P and N increased yield by about 40 per cent compared to the no-fertilizer treatment, but this difference was only significant at the 9 per cent probability level. Fertilizer application resulted in the production of more total heads and more fertile heads per hill. The number of stems per hill for the tiller removal treatment was more than half that for the no removal treatment, indicating that removal may have stimulated subsequent regrowth of tillers. At the higher irrigation level, highly significant interactions were obtained (Table 3). These interactions are shown in Table 4. The cultivar HKP produced significantly (p < 0.05) more fertile mature heads in response to fertilizer application than. cultivar Zongo. The latter tillered more in response to fertilizer P and N. Removal of the tillers did not influence the number of fertile mature heads at harvest for cultivar Zongo but significantly reduced the number produced by cultivar HKP. The climatic data during the growth of the crop were recorded at the Maradi weather station, about 1 km from the experimental site and are summarized

The analysis of variance showed no significant interactions between the treatments. Cultivar HKP significantly outyielded the locally grown cultivar Zongo. The estimated grain yield responses to the additional 76 mm of water applied were 1.1 kg ha- 1 mm- 1 for Zongo, and 3.6 kg ha- 1 mm- 1 for HKP. The cultivar HKP produced more total heads per hill than Zongo. Table 5. -

1

Stems per hill at harvest 1 SED = 0.65

HKP

Zongo

Treatment

Stems per hill at GS6 1 SED = 1.60

Meteorological data averaged over 10-day intervals from 19 February, 1985 through 29 May 1985 from the station at Maradi.

Days in 1985

Sunshine hours

50-59 60-69 70-79 80-89 90-99 100-109 110-119 120-129 130-139 140-149

5.7 5.3 3.2 6.2 5.4 6.1 6.6 7.4 8.4 9.2

Mean values of meteorological variables over 10-day intervals 1 Max. Min. Sat. vapor Angot temp. temp. pressure Vapor Day length value oc oc mb press mb hr mm 31.3 34.5 39.0 38.6 35.1 37.4 39.3 40.6 39.8 39.3

17.3 18.9 25.1 24.8 23.3 24.6 24.7 26.9 27.1 27.7

30.5 35.5 47.8 46.9 40.7 44.9 48.2 52.6 51.9 51.8

4.0 4.9 8.7 13.1 8.9 9.0 6.3 16.9 21.1 22.6

11.8 11.9 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8

14.2 14.6 15.0 15.3 15.6 15.7 15.8 15.8 15.8 15.8

Windspeed km/day

Penman PET mm

234.1 193.9 152.4 74.0 221.4 131.4 167.8 101.0 92.2 118.7

8.49 8.15 7.56 6.35 8.82 7.61 8.80 7.29 7.11 7.60

Angot value is the equivalent in mm of water of the daily solar radiation in the absence of the atmosphere. Eur. J. Agron.

45

Management of dryland pearl millet in Niger

Table 6. - Effect of cultivar, fertilizer, and tiller removal on moisture storage in the 2 m depth of profile at harvest, and on weight of fertile sun-dried heads per ha per mm of moisture balance for the low and high irrigation levels in experiment El at Tarna. Treatment or Statistic Overall mean cv% SED 1

Cultivar Zongo HKP Fertilizer None Recommended rates of N, P Tiller removal None 50 % removed at GS4 and GS6

1 SED Error *, ** There

Moisture stored at harvest (mm) Irrigation Irrigation = 233 mm = 309 mm

kg heads ha- 1 mm· 1 of moisture balance Irrigation Irrigation = 233 mm = 309 mm

69.0 16.7 4.7

96.5 13.2 5.2

2.86 31.6 0.37

3.33 47.4 0.65

65.1 72.9 ns

92.0 101.0 ns

2.19 3.53 **

2.21 4.46 **

75.3 62.7 **

101.4 91.7 ns

2.54 3.19 ns

2.83 3.84 ns

66.7 71.4 ns

95.7 97.3 ns

2.92 2.80 ns

3.36 3.31 ns

= The standard error of a mean difference for a given observation is the same for all 3 factors. df for mean comparison= 14. denotes significant differences at P = 0.05 and 0.01 respectively; ns = not significant. were no two or three-way interactions.

in Table 5. This period was characterized by high temperatures and persistent, dry winds. The mean decadal potential evapotranspiration (PET) was calculated by Penman's method using coefficients proposed by Doorenbos and Pruitt (1977). From Table 5, the total Penman PET during the 100 days between 19 February and 25 May 1985 was 778 mm. The low and high irrigation levels represent 30 per cent and 40 per cent, respectively, of this estimated PET. A mean initial water storage of 28.8 (± 5.6) mm in the 0-200 em profile depth was calculated from the soil moisture data taken before the initial irrigation. The moisture storage at harvest in this profile depth, calculated from the results of the soil sampling done at harvest in all the treatment plots, is presented in Table 6. The overall mean storage at harvest was about 50 per cent greater at the higher irrigation level. Water storage at harvest was not influenced by the treatments, except for the fertilized plots at the lower irrigation level. The moisture balance (initial mean moisture storage of 28.8 mm + the irrigation applied - the storage at harvest), was taken as the actual evapotranspiration (AET) by the crop. The water use efficiency, calculated as kg of sun-dried, fertile, mature heads per mm of the estimated AET for the various treatments are also presented in Table 6. The overall mean AET values were 193 mm and 241 mm for the low and high irrigation levels, respectively. The water use efficiency was much greater for cultivar HKP than for cultivar Zongo. Vol. 2, n° I- 1993

Fertilizer and tiller removal had no significant effect on the water use efficiency. The mean height of elongating main stems on eight dates after tiller removal for the low and high irrigation levels respectively are presented in Tables 7 and 8. Height was influenced more by cultivar or fertilizer application at the higher irrigation level. At the lower irrigation level, removal of the tillers resulted initially in significantly (p < 0.05) taller stems, but this effect was not sustained at the later sampling dates. The overall results of this experiment did not establish any direct beneficial effect of tiller removal. An indirect benefit is that the tillers removed can be used as fodder. The sun-dried weights of tillers removed at GS4 were equivalent to 99 kg ha- 1 for the low irrigation level and 121 kg ha - 1 for the high irrigation level. The results clearly indicated that both fertilizer level and cultivar can be varied to produce better growth. Experiment E2 The results of the observations taken at harvest of pearl millet grown under rainfed conditions are presented in Table 9. A significant increase (p < 0.05) in grain yield was obtained by removal of the tillers at GS4. This increase appeared to be the result of larger and more fertile heads. Experiment E1 did not show any definite direct benefit from tiller removal. A more

46

N. Persaud et al.

Table 7. - Effect of cultivar, fertilizer, and tiller removal on mean height of elongating main stems of pearl millet at the low irrigation level in experiment El at Tarna. Mean height (em) of elongating stems measured on eight dates in April 1985

Treatment or Statistic Overall mean CV% SED 1

Cultivar Zongo HKP Fertilizer None Recommended rates of N, P Tiller removal None 50 % removed at GS4 and GS6

01/04

04/04

09/04

12/04

15/04

19/04

23/04

30/04

73.1 8.5 2.5

85.6 6.9 2.4

94.3 8.0 3.1

106.5 9.0 3.9

119.9 10.5 5.2

130.3 12.4 6.6

137.7 13.1 7.4

149.3 12.6 7.7

72.2 73.9 ns

84.4 86.9 ns

92.6 96.1 ns

101.7 111.2

*

114.6 125.1 ns

124.7 135.9 ns

133.0 142.5 ns

151.6 147.0 ns

72.5 73.6 ns

84.2 87.1 ns

92.5 96.2 ns

104.2 108.7 ns

117.4 122.4 ns

128.3 132.4 ns

136.9 138.5 ns

149.5 149.1 ns

69.6 76.5

82.8 88.5

91.6 97.1 ns

104.0 109.0 ns

115.0 124.7 ns

126.2 134.4 ns

132.9 142.5 ns

145.8 152.8 ns

*

** 1

SED= The standard error of a mean difference for a given date is the same for all 3 factors. Error df for mean comparison = 14. *, ** denotes significant differences at P = 0.05 and 0.01 respectively ; ns = not significant. There were no two or three-way interactions.

Table 8. - Effect of cultivar, fertilizer, and tiller removal on mean height of elongating main stems of pearl millet at the high irrigation level in experiment El at Tarna. Mean height (em) of elongating stems measured on eight dates in April 1985 Treatment or Statistic

01/04

04/04

09/04

12/04

19/04

23/04

30/04

SED 1

69.6 13.5 3.8

78.1 11.5 3.7

87.9 12.1 4.3

102.8 12.7 5.3

118.6 13.3 6.5

131.2 14.1 7.5

139.5 15.2 8.7

150.6 15.1 9.3

Cultivar Zongo HKP

62.8 76.4

69.9 86.3

78.1 97.6

104.1 133.1

115.9 146.5

126.8 152.1

**

**

**

89.9 115.6

**

**

**

**

145.0 156.3 ns

68.5 70.7 ns

75.6 80.7 ns

82.4 93.4

96.4 109.1

111.7 125.6

*

124.4 138.0 ns

130.8 148.1 ns

146.0 155.3 ns

72.2 67.0 ns

81.0 75.3 ns

90.5 85.2 ns

105.9 99.6 ns

120.8 116.5 ns

133.5 128.9 ns

141.4 137.6 ns

149.0 152.3 ns

Overall mean CV%

Fertilizer None Recommended rates of N, P Tiller removal None 50 % removed at GS4 and GS6

*

15/04

*

1 SED =The standard error of a mean difference for a given date is the same for all 3 factors. Error df for mean comparison = 14. *, ** denotes significant differences at P = 0.05 and 0.01 respectively; ns = not significant. There were no two or three-way interactions.

Table 9. - Effect of tiller removal on yield of grain per hill, mean head weight of fertile sun-dried heads, fertile heads per hill, stems per hill at harvest, dry matter stover at harvest per hill, and threshing percentage for pearl millet in experiment E2 at Kalapate. Weight grain per hill g

Mean head weight g

Number of fertile heads per hill

Number of stems per hill at harvest

Weight of D.M. stover per hill g

Threshing percentage

Overall mean cv % SED 1

66.2 7.5 2.8

44.2 11.5 2.9

2.2 11.4 0.14

6.0 20.8 0.72

133.9 17.7 13.7

65.6 4.0 1.5

Tiller removal None 50 % removed at GS4

63.1 69.3

44.4 43.9 ns

2.1 2.3 ns

6.8 5.3

137.3 130.4 ns

65.3 65.8 ns

Treatment or Statistic

* 1

*

SED = the standard error of a mean difference. Error df for mean comparison = 10.

47

Management of dryland pearl millet in Niger

Table 10. - Effect of cultivar, level of tiller removal, and fertilizer P and N on fertile sun-dried heads per hill, weight sun-dried heads per hill, weight grain per hill, and weight of 1000 grains for experiment E3 at N'Dounga.

Treatment or Statistic Overall mean cv % Cultivar HKP CIVT Local SED' Tiller removal 0% 25 % 50 % 75 % SED' Fertilizer P + 45 kg N P + 65 kg N SED' 1

Number of fertile heads per hill

Weight heads per hill g

Weight grain per hill g

2.64 15.5

118.5 22.8

76.1 25.1

9.1 6.4

2.71 2.50 2.70 ns 0.12

120.5 101.4 133.7

77.6 63.6 87.1

9.4 9.6 8.2

**

**

**

7.8

5.5

0.17

3.26 3.03 2.59 1.67

138.0 131.9 116.5 87.6

86.9 85.7 74.9 56.9

9.0 8.9 8.8 9.7

**

**

Weight of 1000 grains g

**

**

0.14

9.0

6.4

0.20

2.49 2.78

112.1 125.0

72.6 79.6 ns 4.5

9.2 9.0 ns 0.14

**

*

0.10

6.4

SED = standard error of a mean difference. Error df for comparison of means for the 3 factors = 46.

*, ** denotes significant differences at P = 0.05 and 0.01 respectively; ns =not significant. Significant tiller removal x fertilizer interaction for fertile heads/hill.

comprehensive evaluation of tiller removal under rainfed conditions was indicated. Experiment E3

The results of the observations made at harvest for this experiment are presented in Table 10. There was only one significant interaction between the treatments. Grain production was significantly greater (p < 0.05) and grain size was significantly less (p < 0.05) for the locally grown cultivar. Tiller removal greater than 25 per cent significantly reduced (p < 0.05) number and weight of fertile heads produced. Removal of 75 per cent of the tillers resulted in increased (p < 0.05) grain size. The additional 20 kg ha- 1 N Table 11. - Tiller removal x fertilizer interaction for number of fertile heads per hill for experiment E3 at N'Dounga.

Tiller removal 0% 25 % 50 % 75%

Number of fertile heads per hill P + 45 kg N P + 65 kg N 2.87 2.97 2.45 1.67

3.64 3.08 2.74 1.66

SED for comparing tiller removal means at each fertilizer level and for comparing fertilizer means at each tiller removal level = 0.19. Vol. 2,

ll

0

I - 1993

resulted in significant increases (p < 0.05) in the number and weight of fertile heads produced. The effect of interaction between tiller removal and fertilizer application on number of fertile heads per hill is detailed in Table 11. The additional 20 kg ha- 1 N made a significant difference (p < 0.05) to the number of fertile heads produced only when no tillers were removed. This indicated that tiller removal influenced plant response to fertilizer N. The calibration curve for the neutron probe was used to obtain the soil water storage in the plots for the five sampling dates after the tillers were removed. The cumulative rainfall and daily rainfall during the growing period of the crop are shown in Figure 1. Total rainfall was 342.8 mm between 1 July and

E

E

60 E E

400

48

::f 300

36

Lf

z 200

~ ~

::J ()

_j _J

Lf z

24 ~ 12 ~

100

o~~~rl=~~~~~~~~~o ~ 0

10 20 30 40 50 60 70 80 DAYS FROM 1 JULY 1986

90

Figure 1. - Daily and cumulative rainfall from July through September 1986 at the site for experiment E3 at N'Dounga.

N. Persaud et al.

48

30 September and was reasonably well distributed. The soil water balance calculated as the difference, ~p - ~S, of the changes in cumulative rainfall (~P), and total profile storage (~S), between two sampling dates was taken as an estimate of the AET between the two dates. The soil moisture balance calculated in this manner for the four sampling intervals and for the interval between the first and last sampling dates is summarized in Table 12. The total AET accumulated over the entire period was significantly (p < 0.05) less (about 10-15 per cent) for the plots with 50 per cent and 75 per cent of the tillers removed.

The combined results for experiments E 1, E2, and E3 did not establish conclusively that tiller removal had a beneficial effect on growth and productivity of pearl millet. About 25 per cent of the tillers could be removed at GS4 without affecting yields, especially for the locally grown cultivars. Experiment E4 The observations at harvest for the two sites, Malgorou and Tyeleda, are summarized in Tables 13 and 14. The crops appeared to be equally productive at the two sites and the effects of the treatments on

Table 12. - Effect of level of tiller removal on moisture balance in the 0-270 em depth of soil profile of plots with local cultivar fertilized with P + 65 kg Nat several intervals between 28 August 1986 to 20 September 1986 for experiment E3 at N'Dounga. Moisture balance Ll.P - Ll.S mm Treatment or Statistic

28-08-86 to 03-09-86

03-09-86 to 09-09-86

14.3 58.0 11.0

28.9 31.2 41.5

18.4 12.4 12.7 13.6 ns 6.8

27.8 36.3 27.3 24.3 ns 7.4

Overall mean cv % Ll.P Tiller removal 0% 25 % 50 % 75 % SED 1 1

*

09-09-86 to 13-09-86

13-09-86 to 20-09-86

28-08-86 to 20-09-86

19.0 24.0 3.9

18.9 14.8 34.0

81.1 6.4 90.4

16.4 20.8 17.9 20.8 ns 3.7

21.1 18.6 18.0 18.0 ns 2.3

83.7 88.1 75.8 76.7

*

4.2

SED = standard error of a mean difference. Error df for mean comparison for the 4 treatments = 6. denotes significant differences at P = 0.05 ; ns = not significant.

Table 13. - Effect of intercropping of short-(HKP), medium-(CIVT), and long-season local millet cultivar on the number of fertile heads per hill, grain weight per hill, fresh weight stover harvested per hill, head weight, grain weight per head, threshing percentage, and ratio of grain to grain + stover harvested for experiment E4 at Malgorou.

Treatment or Statistic Overall mean o/o HKP CIVT Local HKP-CIVT HKP-Local CIVT-Local HKP-CIVT -Local in lines HKP-CIVT- Local in same hill

CV

I

1

SED

Number of heads per hill

Weight of grain per hill g

Weight od stover per hill g

Head weight g

Weight of grain per head g

3.260 9.2 3.502 3.493 2.582 3.582 3.096 3.087

106.8 15.9 114.5 106.4 93.7 116.6 92.7 109.8

262.6 33.9 252.7 193.8 215.4 293.6 329.8 206.2

48.16 9.1 49.90 46.74 49.03 46.49 46.58 48.54

33.15 20.8 32.78 30.58 37.51 32.51 29.93 35.71

68.7 18.4 65.5 65.4 76.2 69.7 63.9 74.1

26.7 24.8 27.6 30.0 28.0 26.3 19.5 31.3

3.546

106.1

341.8

47.49

29.85

62.9

22.2

3.220

114.4

267.8

*

10.7

56.3

50.54 ns 2.78

36.36 ns 4.35

72.2 ns 8.0

28.7

*

** 0.190

Threshing percentage

Harvest ratio %

4.2

SED =Standard error of a mean difference. Error df for means comparison = 28. Eur. J. Agron.

49

Management of dryland pearl millet in Niger

Table 14. - Effect of intercropping of short-(HKP), medium-(CIVT), and long-season local millet cultivar on the number of fertile heads per hill, grain weight per hill, fresh weight stover harvested per hill, head weight, grain weight per head, threshing percentage, and ratio of grain to grain + stover harvested for experiment E4 at Tyeleda.

Treatment or Statistic Overall mean cv % HKP CIVT Local HKP-CIVT HKP-Loca1 CIVT-Local HKP-CIVT -Local in lines HKP-CIVT -Local in same hill I

1

Weight of grain per hill g

Weight of stover per hill g

Head weight g

Weight of grain per head g

Threshing percentage

Harvest ratio %

3.338 14.5 3.775 3.584 2.500 3.616 2.791 3.522

99.6 20.7 117.2 109.6 67.5 111.9 77.5 107.1

377.2 30.4 439.4 309.4 394.5 403.5 385.6 358.7

48.24 9.2 47.88 48.84 48.02 49.19 45.15 49.82

29.7 16.8 31.65 30.72 26.88 31.16 27.04 30.41

61.3 8.7 66.0 62.7 55.9 63.3 58.8 60.8

18.9 24.9 19.4 22.6 13.3 21.3 14.8 20.4

3.577

101.9

322.8

46.91

28.50

60.8

20.8

3.338

103.7

403.5 ns 72.6

50.11 ns 2.81

31.22 ns 3.15

62.2 ns 3.4

19.0

Number of heads per hill

**

SED

0.305

**

13.1

*

3.0

SED =Standard error of a mean difference. Error df for means comparison = 28.

the number of fertile heads and grain produced were similar. The improved cultivars significantly (p < 0.05) outyielded the locally grown one at both sites. Intercropping with the locally grown cultivar reduced the number of fertile heads and the amount of grain produced by cultivar HKP or cultivar CIVT. At both sites, the amount of fresh stover was greatest for cultivar HKP and least for cultivar CIVT. For some observations, the locally grown cultivars at Malgorou and Tyeleda performed differently relative to cultivar HKP and cultivar CIVT. Both cultivar HKP and cultivar CIVT had a greater threshing percentage than the locally grown cultivar at Tyeleda. At both sites, the number of fertile heads and the amount of grain produced from the simultaneous intercropping of all three cultivars, either in lines or in the same hill, were the same as those produced from cultivar HKP or cultivar CIVT grown alone but were greater than those of the local cultivars grown in pure stands. The results of these two experiments show no benefit from a 50:50 combination of either of the improved shorter season cultivars, HKP and CIVT, with the local, long-season ones. A 1: 1: 1 combination of all three cultivars in rows or in the same hill markedly increased yields over the local cultivars grown alone. Studies over several seasons are required to make firm conclusions on the benefit of this practice.

CONCLUSIONS The results did not show any benefit to yields or water use efficiency from tiller removal. In experiVol. 2,

U

0

I- 1993

ments at two locations, intercropping of the improved short-season cultivars, HKP and CIVT, with local ones increased yields over the local cultivar grown in pure stands but decreased yields compared to the improved cultivars grown in pure stands. Both sets of experiments clearly showed that the improved cultivars, HKP and CIVT, were superior in grain yield to the locally grown ones. The application of fertilizer P and N also benefitted yields but may not be feasible for resource-poor subsistence farmers of Niger.

REFERENCES Azam-Ali S. N., Gregory P. J. and Monteith J. L. (1984). Effects of planting density on water use and productivity of pearl millet grown on stored water l. Growth of roots and shoots. Exp. Agric., 20, 203-214. Azam-Ali S. N., Gregory P. J. and Monteith J. L. (1984). Effects of planting density on water use and productivity of pearl millet grown on stored water II. Water use, light interception, and dry matter production. Exp. Agric., 20, 215-224. Bidinger F. R., Mahalakshmi V. and Rao G. D.P. (1987). Assessment of drought resistance in pearl millet [Pennisetum americanum (L.) Leeke]. l. Factors affecting yields under stress. Austr. J. Agric. Res., 38, 37-48. Doorenbos J. and Pruitt W. 0. (1977). Crop water requirements. FAO Irrigation and Drainage Paper, n° 24, FAO, Rome. Mahalakshmi V. and Bidinger F. R. (1985). Flowering response of pearl millet to water stress during panicle development. Ann. appl. Bioi., 106, 571-578.

50

Maiti R. K. and Bidinger F. R. (1981). Growth and development of the pearl millet plant. Res. Bull., 6, ICRISAT, Patancheru A. P., 502 324, India. Ouattara M. and Persaud N. (1985). Contraintes liees au sol et a l' eau et adaptation a ces contraintes par les paysans 1ocaux lors de la production cerealiere en culture pluviale au Niger. Proc. INTSORMIL Workshop on Collaborative Research in West Africa, Niamey, Niger, October 13-17, 1985. INTSORMIL, University of Nebraska, Lincoln, Nebraska, USA. Persaud N., Ouattara M. and Alfari I. (1986). Analysis of rainfall records and its implications for improving rain use efficiency for cereal production in Niger.

N. Persaud et al.

Proc. OAU/STRCISAFGRAD International Drought Symposium, Nairobi, Kenya, May 19-23, 1986. SAPGRAD, B.P. 1783, Ouagadougou, Burkina-Faso. Stoop W. A. (1987). Adaptation of sorghum/maize and sorghum/pearl millet intercrop systems to the toposequence land types in the North Sudanian zone of the West African savanna. Field Crops Res., 16, 255-272. Vanderlip R. (1987). How a sorghum plant develops. Cooperative Extension Service, Kansas State University, Manhattan, Kansas : Special Publication S-3. Yoshida S. (1972). Physiological aspects of grain yield. Ann. Rev. Plant Physiol., 23, 437-465.

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