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Intercrop Combination and Tillage Practice On Weed Cover Score And  Weed Dry Weight In Maize / Groundnut Mixture In Anyigba, Kogi State,  Nigeria

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Sole maize 
Sole groundnut 
Weed cover 
Weed biomass 
Weed dry weight 
Received: 15.06.2023 
Received in revised  
Accepted: 30.06.2023
There is no reliable study of worldwide damage due to weeds. However,  it is widely known that losses caused by weeds have exceeded the losses from any category of agricultural pests such as insects, nematodes, and diseases. Trials were conducted in the rainy seasons of 2020 and 2021,  at Latitude 70 301 and Longitude 70 091 E in the Southern Guinea  Savannah agro-ecological zone of Nigeria to evaluate the effect of tillage practice and crop combination on weed incidence. The treatment consisted of five intercropping patterns and three tillage practices in a  factorial experiment (tillage practices and intercropping pattern)  assigned in a Randomized Complete Block Design with four replications.  Analyzed data at 3WAP, 6WAP, and 6WAP show a significant (p≤0.05)  effect of intercrop combination on Weed Cover Score in the 2021  cropping season though no such significance was observed in the 2020  season. Analyzed data also show a significant (p≤0.05) effect of planting pattern on weed dry weight in the 2021 cropping season though no such significance was observed in the 2020 season. Regarding tillage practice,  non-significant (p≥0.05) effects of tillage practice on weed dry weight were observed in the 2020 cropping season, which was also at variance with the significant (p≤0.05) effect of tillage practice observed on weed dry weight in 2021 season. For both seasons, there were consistencies in the outcomes, with the highest weed dry weight observed in the Zero tillage followed by seeding on the flat and lastly when seeds were sown on ridges. Unless mitigated the highest crop losses should be expected  on Zero tillage plots with the least when seeds are sown on ridges


In sub-Sahara Africa, about 70% of farmers are smallholders accounting for 90 percent of the total farm output characterized by poor yields arising from production constraints such as diseases, pests, and weeds (Cadini and Angelucci, 2013; Oyewole and Ibikunle, 2010; Oyewole et al. 2012). Of all the  

constraints weed competition is the most critical and poses the greatest problems on traditional arable crops, thus threatening food security in the sub-region (Dixit et al., 2008; Oyewole and Ibikunle, 2010;  Oyewole et al. 2012). The economic losses due to weed competition are now recognized as major obstacles in maize production.

More so, maize being a sensitive crop is highly vulnerable to weed infestation particularly during the first four weeks of its life hence  varying degrees of percentage reductions caused by  weed interference have been reported in the crop  (Adigun and Lagoke, 1999). For instance; uncontrolled  weed growth in pure maize fields has led to about 60  to 65% and 40 to 60% suppression in the overall grain  yields of the crop from different ecological zones of  Nigeria (Badmus et al. 2006). 

Weed management is the most challenging  component of maize production. Successful weed  control is important for achieving maximum yield in  maize grain and silage crops. Weeds that are not  controlled compete for light and the crop’s nutrient  and water resources, and yield losses may be up to 70%  of the potential yield. Although many maize farmers  have developed successful management practices for  weed control there are instances when weeds become  a problem.

These include times when herbicide use  fails because of environmental conditions, weeds become resistant to recommended herbicides or the  crop is being grown on leased land where weed control has been poor in the past. Effective weed control in  maize requires attention to detail. If weeds get away there are immediate and ongoing losses for the maize  grower (FAR Focus, 2013).

The critical time for weed control in maize is between crop emergence and canopy closure. Weeds may emerge at any time during  this period but are more likely to appear after rain.  Successful weed management depends firstly on  knowing what you are trying to manage. This may not be as easy as it sounds as most weed management practices depend on an early strike at the weed, when it has just two to four leaves. At this growth stage, all weeds may look similar, especially grass weeds (FAR  Focus, 2013). 

Weeds affect everyone in the world by reducing crop  yield and crop quality, delaying or interfering with  harvesting, interfering with animal feeding (including  poisoning), reducing animal health, preventing water  flow, as plant parasites, among others. Weeds are  common everywhere and cause crop losses annually,  with the global cost of controlling weeds running into  billions of dollars (Kraehmer and Baur, 2013).

The potential crop yield loss without weed control was  estimated at 43% on a global scale (Oerke, 2006).  While, (Rao, 2000) has reported that, of the total  annual loss of agricultural produce from various pests,  weeds account for 43%, insects 30%, diseases 20%, and other pests 5%. Annual worldwide losses to weeds  were estimated to comprise approximately 10-15% of  attainable production among the principal food  sources. Reduction in crop yield has a direct correlation  with weed competition. Weeds are the most acute pest  in agriculture with an estimated annual global damage  of around 40 billion dollars per year (Monaco et al. 2002). Generally, an increase in one kilogram of weed  growth corresponds to a reduction in one kilogram of  crop growth (Rao, 2000).  

The yield of maize obtained in Nigeria is far below  expectation due to numerous factors which include  weed infestation, low soil fertility and availability of  labor. Yield losses of between 60–80% have been  attributed to uncontrolled weed infestation in maize  (Lagoke et al. 1998) and this finding was confirmed by  (Imoloame and Omolaiye, 2016), who reported 89%  yield loss in maize as a result of uncontrolled weed  infestation. Weed infestation is of supreme  importance among biotic factors that are responsible  for low maize grain yield. Worldwide maize production  is hampered up to 40% by competition from weeds  which are the most important pest group of this crop  (Chikoye et al. 2004).  

Also, the main problems limiting the production of  groundnut are poor cultural practices and inadequate  weed management. Weed causes much damage to the  groundnut crop during the first 45 days of its growth.  Reports have shown that groundnut cannot compete  effectively with weeds, particularly 3-6 weeks after  sowing. The average yield loss due to weed is about  30%; while at ICRISAT 100% yield loss has been  observed. Therefore, early removal of weeds is important before flowering and during pegging (Page  et al. 2002).

If early weeding is done well, and crop  spacing recommendations followed, then the weeds that come up later are smothered with the vigorous  growth of the crop. Once flowering and pegging begin  it is advisable to weed by hand pulling rather than by  using hoe, as this is less likely to disturb any developing  pods. Weed management rather than complete  eradication of weed is the intent to regulate the  population and maintain appropriate weed levels,  taking into account both economic and ecological  aspects that is, at a threshold level that does not cause  economic loss to the crop and also does not adversely  affect the environment (Harkansson, 2003). 

The growth of groundnut is slow initially and the crop  forms only a thin canopy offering little competition to  most weeds at the stage (Zimdahl, 1980). Uncontrolled weed growth has been reported to cause a yield  reduction of 50-80% in groundnut. Weed depresses  groundnut yields by competing with the crop for light,  minerals, and nutrients and also harvest operations.

It is therefore important that weeds be controlled for  profitable production (Brecke and Colvin 1991). With  the increasing reports of negative environmental  effects of continuous use of pesticides, the need to  either totally eliminate or reduce its usage cannot be over-emphasized; an important key to this is the  employment of agronomic practices, which may assist  in achieving either reduction or elimination of pesticide  utilization among farmers. The above justifies a study  on cropping patterns and tillage practices on weed  parameters in the study area.  

The need to maximize land productivity in the humid  tropics has become more evident (Steiner, 1991). This  has not been achievable with monoculture with single  harvests per season, as gains in production per unit  area under this system have not been impressive in the  tropical environment (IITA, 1990). Intercropping of two  or more crops especially the family Poaceae with  Fabaceae is popular in many countries because yields  are often higher than pure cropping systems  (Lithourgidis et al. 2006). 

Tillage is crucial for crop establishment, growth, and ultimately, yield (Atkinson et al. 2007). A good soil management program protects the soil from water and wind erosion, provides a good, weed-free seedbed for planting, destroys hardpans or compacted layers that may limit root development, and allows maintenance or even an increase of organic matter (Wright et al.,  2008).

Many farmers perform tillage operations  without being aware of the effect of these operations  on soil physical properties and crop responses (Ozpinar  and Isik, 2004). Poor crop establishment and low soil  fertility are particularly constraining for crop  production. Tillage practice is therefore key as  cultivation implements impose varying degrees of  alterations to both the surface soil and sub-soil. As such  it is crucial to determine the best practice for tillage  practices to maximize crop establishment and yield. 


Trial was conducted in the rainy seasons of 2020 and  2021 in Latitude 70 301 and Longitude 70 091 E in the  Southern Guinea Savannah agro-ecological zone of  Nigeria. The experiment sited at the Kogi State  University Anyigba Students’ Research and Demonstration Farm consisted of five intercropping patterns Sole Maize, Sole Groundnut, Two rows of  maize and one row of groundnut, Two rows of  groundnut and one row of maize, One row of maize  and one row of groundnut and three tillage practice  methods (planting on ridge, planting on flat land and  zero tillage). Factorial combinations of the treatments  (tillage practice and intercropping pattern) fully  randomized were laid out in a Randomized Complete  Block Design with four replications. Plot size measuring  3m x 4.5m (sixty plots) were used for the experiment. 

For the tillage practice involving planting seeds on the  flat, the land was ploughed, harrowed and made into  flat beds, while for those crops sown on the ridge, the  experimental site was ploughed, harrowed and ridged  75cm apart while for the zero tillage, conventional  tillage practices were not done before seed sowing.  Factorial combinations of these treatments (tillage  practice and intercropping pattern) fully randomized  were laid out in a Randomized Complete Block Design  with four replications. Plot sizes measuring 3m x 4.5m  (sixty plots) were used for the experiment. 

One improved variety of maize (TZESR) and one local  variety of groundnuts (Angba-chido) obtained from  IITA – Ibadan and ADP Anyigba, Kogi state, respectively  were used. Row replacement methods were employed  in seeding the groundnut plots; moving from sole  cropped plots, which were then gradually replaced  with rows of maize until attaining sole maize plots. 

While the groundnut stands were seeded 23 cm x 75  cm, the maize stands were seeded 25 cm x 75 cm. Two  seeds of groundnut as well as maize were planted per  hole, which were thinned to one seedling per stand at  two weeks after planting (2 WAP). NPK 15:15:15 was  applied to all the plots as the basal application (45kg  N/ha, 45kg P2O5 and 45kg K2O/ha) and top dressed  with Urea at 6 WAP. Percentage seedling emergence  was determined ones at two weeks after planting (2  WAP). 

An average of three quadrant throws were used in the determination of weed parameters (weed floral, weed  cover score, weed biomass) at 3, 6 and 9 WAP after cropping. For weed dry weight samples within the quadrant throws were oven-dried at 750C for 48 hours and allowed to cool before weighing using the Metler  Toledo electric weighing scale. For Weed Cover Score,  a scale of 1 – 9, was used where 1 was complete  absence of weeds, and 9 was complete coverage of the plot by weeds. All weed data were transformed using the square root transformation method before analysis. 


Effect of Planting Pattern, Tillage Practice, and Their Interactions on Weed Cover Score: 

Weed infestation is reported to be of supreme  importance among biotic factors that are responsible  for low maize and groundnut yields (Selvakumar and  Sundari, 2006). Analyzed data at weeks 3, 6, and 9  show a significant (p≤0.05) effect of intercrop  combination on Weed Cover Scores in the 2021  cropping season though no such significance (p ≥ 0.05)  was observed in the 2020 season (Table 1) at week 3, 6  and 9.

The significant effect of intercrop on Weed  Cover Score in the 2021 cropping season, is similar to  the observation made by Rao (2000) and Hamzei. and  Seyedi (2015), of the significant effect of intercropping  on weed suppression in maize, but Rao (2000)  emphasizes that intercropping system alone is not sufficient to ensure adequate weed management  practices, because of varied canopy coverage occurrence among the intercrops.

The variation in  observation between seasons is in line with Oyewole  (2004) who observed that research outcomes could  vary between seasons due to various factors, such as  weather, pests, and agronomic factors, among other  reasons. In both cropping seasons, among sole crops,  sole maize performed better than sole groundnut in  reducing Weed Cover Score, thus lowered Weed Cover  Scores were consistently observed in sole maize when  compared with sole groundnut (Table 1).

The  observation is understandable, noting that maize, as an  erect and taller crop, should be better at shading than  the crawling groundnut (Oyewole, 2004). In the 2020  and 2021 cropping seasons, the more the inclusion of  maize stands among the intercrops, the more the  reduction in Weed Cover Scores (Table 1), which could  translate into an increase in yield as observed by  Oyewole, (2016), who noted that observed  reduction in Weed Cover Scores is likely to affect the  competitive ability of the associating weeds negatively. 

Table 1: Effect of planting pattern, tillage practice, and their interactions on Weed Cover Score 

Treatment Weed cover score (Scale of 1 – 9)
2020 2021
Intercrop Combination
Sole maize 1.401.431.382.75ab 3.233.62a
Sole groundnut 1.581.621.493.003.493.85a
2maize:1g/nut 1.521.581.452.252.582.63b
2g/nut:1maize 1.691.691.522.38bc 2.662.72b
1maize:1g/nut 1.541.591.522.42bc 2.592.70b
LSD (0.05) 0.43ns 0.43ns 0.19ns 0.37* 0.27* 0.37*
Tillage (T)
Ridge 1.421.461.432.232.632.93b
Flat 1.521.511.532.282.842.94b
Zero Tillage 1.701.781.473.183.263.45a
LSD (0.05) 0.33 ns 0.33 ns 0.15 ns 0.28* 0.21* 0.28*
P x T ns ns ns ns ns ns
C.V % 13.70 13.2 15.1 17.4 11.1 14.3

As par tillage practice, data collected at week 3, 6 and  9 indicate non-significant (p≥0.05) effect of tillage  practice on Weed Cover Scores in 2020 cropping  season, which was at variance with the significant  (p≤0.05) effect of tillage practice observed in 2021  season (Table 1) within the same period. In both  

seasons, there were consistencies in the outcomes  among tillage practice, with the highest Weed Cover  Scores observed in the Zero tillage followed by  seeding on the flat and lastly when seeds were sown  on ridges; even where such were not statistically  significant, such as in 2020 cropping season. No significant interactions were observed between  intercrop combination and tillage practice on Weed  Cover Scores at 3WAP, 6WAP, and 9WAP in the 2020  and 2021 cropping seasons.

Generally, tillage practice played a significant role in moderating Weed Cover  Scores, where Zero tillage encouraged higher Weed  Cover Scores in both seasons. Since the reduction in  crop yield has a direct correlation with weeds, to  mitigate their effects where Zero tillage is practiced,  there may be the need for some form of weed control  mechanisms, such as the use of herbicides. With a  Weed Cover Score range between 1 – 9, where 1 was an indication of a plot devoid of weeds, a score of 9  for a plot completely covered by weeds, the least  score observed in the 2020 cropping season was 1.39  while the highest Weed Cover Score was 1.69.

In the  2021 season, the least Weed Cover Score was 2.25  while the highest Weed Cover Score was 3.85. With  Weed Cover Scores ranging between 1.39 and 3.85  across seasons, was an indication of plots either  almost weed-free to plots about 1/3 covered by  weeds. 

Table 2: Effect of planting pattern, tillage practice, and their interactions on Weed dry weight (g/m2) in 2020  and 2021 cropping season 

Treatment Weed dry weight (g/m2)
2020 2021
Intercrop Combination
Sole maize 20.6620.669.8527.2621.7913.85a
Sole groundnut 18.2518.199.9227.0620.53ab 13.12a
2maize:1g/nut 19.6119.479.7022.6918.2011.62b
2g/nut:1maize 20.1620.139.9923.1518.3612.83ab
1maize:1g/nut 20.0019.749.1120.9017.8512.73ab
LSD 3.23ns 3.47ns 1.20ns 2.73* 3.27* 1.82*
Tillage (T)
Ridge 18.7418.509.2121.75 16.6511.26b
Flat 18.98ab 18.9ab 9.9622.0217.4511.69b
Zero Tillage 21.4821.519.9828.8623.9415.53a
LSD 2.50* 2.70* 0.93ns 2.12* 2.53* 1.41*
P x T ns ns ns ns ns ns
C.V % 19.8 21.5 15.0 13.7 20.5 17.2

Effect of Intercrop Combination, Tillage Practice, and  Their Interactions on Weed Dry Weight 

Analyzed data show a significant (p ≤ 0.05) effect of  planting pattern on weed dry weight in the 2021  cropping season though no such significance was  observed in the 2020 season (Table 2). Regarding  tillage practice, non-significant (p≥0.05) effects of  tillage practice on weed dry weight were observed in  the 2020 cropping season, which was also at variance  with the significant (p≤0.05) effect of tillage practice  observed on weed dry weight in the 2021 season.

For both seasons, there were consistencies in the  outcomes, with the highest weed dry weight observed  in the Zero tillage followed by seeding on the flat and  lastly when seeds were sown on ridges.  

Unless mitigated, the highest crop losses should be  expected on Zero tillage plots with the least where  seeds were sown on ridges. The report has shown that  an increase of one kilogram of weed growth  corresponds to a reduction in one kilogram of crop  growth (Rao, 2000). No significant interactions were  observed between intercrop combination and tillage  practice on weed dry weight at 3WAP, 6WAP, and  9WAP in the 2020 and 2021 cropping seasons. 

Effect of Intercrop Combination, tillage practice, and  their interactions on Maize and groundnut yields in  2020 and 2021 cropping seasons: 

Generally, crops have been grown under conventional  agricultural practices in Nigeria for years (Antenyi,  2021). The basis for conventional tillage is annual ploughing or tilling of the soil, but this is usually  supplemented with a number of other practices,  including the removal or burning of crop residues,  land leveling, harrowing, fertilizer application, and incorporation; all of these practices cause soil  disturbance, compaction, and deterioration, with  anticipated effects on crop yields (Antenyi, 2021). 

Table 3: Effect of Intercrop Combination, tillage practice, and their interactions on maize cob weight and  seeds/cob in the 2020 and 2021 cropping season 

Treatment 2020 cropping season 2021 cropping season
Cob  Weight  (t/ha) Seeds /  cob Grain  Yield  (t/ha)Land  Equivalent  RatioCob Weight  (t/ha)Seeds /  cob Grain Yield  (t/ha) Land Equivalent  Ratio
Intercrop Combination
Sole maize 207.33316.252.37a– 954.322492.335.95a
2maize:1g/nut 107.59256.751.571.28 437.651133.504.541.19
2g/nut:1maize 108.67254.831.701.29 472.221199.254.771.28
1maize:1g/nut 103.27271.171.701.38 481.481205.424.651.32
LSD 23.527* 51.000* 0.44* – 32.660* 271.050* 0.346*
Tillage (T)
Ridge 87.51216.051.371.06 414.441026.653.881.38
Flat 101.19223.801.531.25 515.191434.954.081.40
Zero Tillage 95.07219.551.511.28 477.781156.703.991.42
LSD 33.715ns 39.510ns 0.344ns 22.757* 209.951* 0.265ns
P x T ns ns *
C.V % 21.4 28.2 26.0 25.4 27.3 10.3

Maize (Table 3), Stover yield responded significantly  to intercrop combination as well as tillage practice in  both cropping seasons. However, 100-seed weight  was not significantly (P≥0.05) influenced by intercrop  combination, tillage practice, or their interactions in  both cropping seasons. Planting maize seeds on the  flat gave the best grain yield, with maize seeds planted  on ridges giving the lowest grain yield in both seasons. 

On the groundnut component of the mixture (Table  4), Haulm yield/ha, pod yield/ha, harvest Index (HI), and shelling percentage responded significantly to  intercrop combination in both cropping seasons, while  100-seed weight responded to intercrop combination  only in 2021 cropping season.

No significant effect of  tillage practice was observed on all parameters taken  nor were there significant interactions between  intercrop combination and tillage practice on the  investigated parameters; an indication that tillage was  not a necessary treatment in groundnut cultivation in the study area. Relative to LER, among intercrop combination, the highest LER were observed when  one row of maize was intercropped with one row of groundnut, with the least LER observed when two  rows of maize were intercropped with one row of groundnut.

This was similar to observations made by  Oyewole (2004), in a millet/groundnut intercrop in the  Sudan savanna ecological zone; where he observed  that intercropping was generally advantageous when  compared with sole cropping. Also, the observation  was similar to the findings by Antenyi (2021), where  intercropping was observed to be better than sole  cropping in a maize/cassava intercrop. Finally, among  the tillage practice, zero tillage gave the highest LER  with planting on ridges giving the least LER. 

Intercropping was generally advantageous, an  observation that was in line with Oyewole (2004),  Selvakumar and Sundari (2006), and Hamzei. and  Seyedi (2015).

Table 4: Effect of Intercrop Combination, tillage practice, and their interactions on days to flowering and yield-related parameters in 2020 and 2021 cropping  seasons

Treatment Days to Flowering Haulm Yield (kg/ha) Pod yield (kg/ha)Harvest Index (%)100-seed  weight (g)Shelling %
2020 2021 2020 2021 2020 2021 2020 2021 2020 2021 2020 2021
Intercrop Combination
Sole groundnut 32.67 26.83 711.11637.041532136753.2636.7447.83 48.3261.0079.42a
2maize:1g/nut 34.17 28.17 355.56289.891283122628.3222.6444.83 39.7653.1760.65b
2g/nut:1maize 33.25 27.67 362.96266.671332123433.23bc 23.4844.83 38.5554.2054.18b
1maize:1g/nut 33.33 28.83 377.78266.671384122138.4422.1444.83 38.7955.1954.96b
LSD (0.05) 1.600ns 2.830 ns 77.120* 66.100* 70.6* 27.8* 7.060* 2.780* 4.000ns 4.980* 5.080* 6.500*
Tillage (T)
Ridge 27.50 22.40 311.11 310.11 1276 1212 27.67 21.24 35.80 31.59 43.47 49.56 a
Flat 26.35 22.10 377.78 288.89 1322 1204 32.20 20.42 36.70 32.19 44.55 51.23 a
Zero Tillage 26.20 22.40 378.78 288.89 1320 1213 32.08 21.34 36.90 35.48 46.12 48.74 a
LSD (0.05) 1.240ns 0.640ns 67.900ns 78.790ns 54.7ns 21.5ns 5.470ns 2.150ns 3.100ns 3.860ns 3.940ns 5.040ns
P x T ns ns ns ns ns ns ns ns ns ns ns ns
C.V % 7.3 4.5 28.9 31.1 27.9 16.1 27.9 16.1 13.3 18.3 13.8 15.8


Weed management is the most challenging  component of maize production. Successful weed  control is important for achieving maximum yield in  maize grain and silage crops. Weeds that are not  controlled compete for light and the crop’s nutrient  and water resources, and yield losses may be up to  70% of the potential yield. Although many maize  farmers have developed successful management  practices for weed control there are instances when  weeds become a problem.

For both seasons, there were consistencies in the outcomes, with the highest weed dry weight observed in the Zero tillage followed by seeding on the flat and lastly when seeds were sown on ridges. Thus, unless mitigated the highest crop losses should be expected on Zero tillage plots with the least when seeds are sown on ridges.

 Intercropping was generally advantageous compared with sole cropping, thus recommended for the experimental area. Generally, the inclusion of maize in the system had a positive effect on both Weed Cover  Scores as well as Weed Dry weight; as reductions in these parameters were observed. However, higher maize population inclusion in the mixtures may give better results and should be encouraged. 


We acknowledge the Department of Crop Production,  Kogi State University Anyigba, the Faculty of  Agriculture of the same institution, as well as the  University for providing the enabling environment to  conduct this research. 


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Rainfall Data For 2020

JANUARY 0.0 19.6 23.8
FEBRUARY 0.0 20.6 26.5
MARCH 4.1 24.6 27.0
APRIL 1.7 25.1 27.7
MAY 3.6 24.5 27.0
JUNE 3.9 23.9 25.2
JULY 9.8 23.6 25.5
AUGUST 5.0 23.4 25.2
SEPTEMBER 6.1 23.5 24.4
OCTOBER 11.1 25.4 26.2
NOVEMBER 0.52 25.3 27.8
DECEMBER 0.00 20.5 25.3