Southern Agricultural Research Institute, Hawassa Research Center, Ethiopia.
Recent developments in small scale agriculture call for minimum soil disturbance in crop production but crop varieties specific to conservation tillage are needed to be used by farmers. A field experiment was conducted at three selected districts of southern nation’s nationalities and people’s region during 2017and 2018 cropping seasons to evaluate the growth and grain yield response of maize varieties to conservation tillage (minimum soil disturbance, residue retention, and herbicide application). The experiment was laid out in randomized complete block design consisting of five varieties (016K-SPRH, 016k-SBRH, BH-540, BH-546, and BH-547) within three replications. Pre planting herbicide (roundup) sprayed to control pre emerged weeds. Growth and yield parameters of maize were measured. Combined analysis of variance over 2017 and 2018 across locations revealed that the maize BH-546 and BH-547 had higher grain yield (5.2 and 5.0 t ha-1), but not significantly higher than the BH 540 (4.9 t ha-1). Although the varieties 016K-SPRB and 016k-SBRH gave lower yield than the hybrids, their performance in growth across locations over years was attractive. The highest plant height (208cm), ear height (108cm) with statistically similar above ground biomass of the varieties to that of the hybrids indicated the potential of materials for further research. Moreover, these varieties performed significantly adaptive and meaningful growth and yield indicating conservation tillage cannot affect the performance of maize growth and yield across locations over years.
Candidate; Conservation; Conventional; Districts; Genotype; Variety
Maize (Zeta mays) is one of the most important cereal crops in the world which is ranked second to wheat production, first in Africa and Latin America but third after rice and wheat in Asia. Globally, maize is grown over an area of 193 million hectares with production of 1.15billion tons annually . The crop is the most important staple crop in the region, feeding more than 200-300 million people across Africa and providing food and income security to millions of smallholder farmers. In Ethiopia, it is grown on over 2 million hectares and ranked first among cereal in total production and productivity. According to the Central statistical agency (CSA) (2018/19) report of the country, maize covered 22.9 % (2.37 million hectares) of the cereal crop area and contributed to 34.2% (94.5 million tons) of the cereal production. In Southern Nations, Nationalities and Peoples Regional State (SNNPRS) of Ethiopia, maize covered 37 % (322714.36 hectares) of the cereal crop area and contributed to 51% (1085725.6 tons) of the cereal production with 3.36 t ha-1 productivity . In spite of the enormous uses of maize and higher volume of production, its productivity in the region is generally low, ranging from 2.2 t ha-1 (Segen people’s zone) to 4.0 t ha-1 (Silte zone ). This is far below the potential yield of maize that could be achieved with the currently available technologies in the country. The world agricultural scenario indicates that food security is the overriding concern of every nation. All technological advances in both developed and developing countries must gear towards increasing food production. Both the largescale, specialized commercial agriculture and small-scale mixed semi-subsistence types of agriculture play vital roles to attain this objective. Prioritization of cost reducing, yield enhancing and resource conserving farming methods is vital to catalyze a shift towards sustainable and resilient maize agri-food systems.
Shortage of additional land for crop production, lack of crop varieties, decreased soil fertility and declining yield for major food crops have been cited as the major concerns for agriculture’s ability to provide nourishment for the increasing population. Increased yield, disease resistant and quality are the ultimate goals in almost any crop improvement programs. However, it seems that reasonable yields with few risks are preferable than high yields with high risks to the resource poor farmers living in the tropics under highly variable environments. Conservation agriculture (CA), is based on minimum soil disturbance, permanent soil organic cover, and the use of diverse crop rotations/associations, has the potential for addressing the current food insecurity and soil degradation on smallholder farming systems . Thus, the present study initiated to evaluate maize varieties compatible under conservation tillage to provide sustainable yield without degrading the farm land through repeated plowing.
Field experiments were conducted during 2017 and 2018 cropping seasons at three locations namely; Halaba on station with clay loam textured soil having pH 6.8 =, EC = 0.08 ds/m, total N (%) = 0.44, available P = 37.6 ppm) and altitude of 1800 m.a.s.l. whereas, Boricha located at 6.93o latitude of and 38.42o longitude having initial soil pH value of 6.32, 2.44 OC, 0.17 total N and 25.93 CEC, and Lokaabaya having 7.10o latitude and 38.15o longitude with 6.15 pH, 2.75 OC, 0.20 total N, and 24.88 CEC, using farmers field as representing location in Southern region of Ethiopia. There is bimodal rainfall pattern locally termed belg (short rainy season starting from February and ends late May) and meher (main rainy season starting from early June and ends late September).
Experimental design and treatments
Treatments consisted of five maize varieties include 016K-SPRH, 016k-SBRH, BH-540, BH546, and BH547, which are intermediate maturing, three-way cross hybrids released for high-potential maize growing areas (Table 1). The treatments were laid out in a randomized complete block design (RCBD) with three replications. Pre emergence herbicide(roundup) was sprayed a week before sowing of maize to control and facilitate weed free field for ease of making rows to plant. Planting was carried out soon after the onset of rainfall and planting time of respective areas. A 4 x 4 m plot size used and maize was planted at inter and intra row spacing of 80 and 25 cm, respectively. Two seeds were placed per hill and after emergence seedlings were thinned to maintain 80 plants per plot. The recommended phosphate in forms NPS was applied at planting whereas N fertilizer applied in split where the first half at planting and second half applied 40 days after planting. Weeding and cultivation were carried out as desired during growing season.
|Variety||Year of release||Altitude
|Rainfall (mm)||Yield (kg ha-1)|
|Research field||Farmers field|
Table 1: Description of maize varieties tested for their growth and yield performance under conservation tillage.
Data recorded were plant height, ear height, above ground biomass yield, thousand seed weight, and grain yield. Harvest Index was calculated as grain yield divided by its biomass yield. Plant height and ear height were measured for five randomly selected plants per plot. Grain was manually harvested from central rows and converted to kg ha-1 after adjusting the moisture content to 12.5%. Biomass yield was estimated as the sum of stover weighed and grain yield. Thousand seed weight (TSW) was measured by counting a thousand seeds manually and weighing it with sensitive balance.
Data were combined across locations over years after carrying out the homogeneity test of variances (Gomeze and Gomez, 1984) and subjected to analysis of variance using the general linear model SAS version 9.1 (SAS INST, 2003). Treatment means were compared using the least significant difference (LSD) at 5% level of significance.
As presented in Table 2 most of the growth and yield parameters tested were statistically significant due to the effects of year, location variety and year by location interaction. The interaction between year X variety and location X variety were highly significant only to thousand seed weight.
|Source of variation||df||Plant height||Ear height||Biomass height||Grain yield||Seed weight||Harvest Index|
Table 2: Mean square values of plant height, ear height, aboveground biomass, thousand seed weight, grain yield and harvest index response of maize varieties to conservation tillage during 2017 and 2018 cropping season
The effect of Year on growth and yield of maize varieties
The effects of year on plant height, ear height, grain yield and HI were significant where 2018 provide significantly better than 2017 across the parameters (Table 3). The most probable reason for this difference is amount and distribution of rainfall, which was better during 2018 than that of 2017 (Figure 1). Bimodal rainfall pattern is common, but the spread over the months differs between areas. There are ‘good’ rainfall years and ‘bad’ rainfall years which are defined not only by variations in overall precipitation but by irregularities such as a late start to the belg rains which seriously delays maize seeding or dry spells at critical periods of growth which much reduce the grain or tuber formation in plants that otherwise look quite healthy. In the lowlands it is not always clear what is real rainfall ‘irregularity’ and what is within a locally quite normal range of inter-annual variation. Total precipitation of Halaba and Boricha where the experiments conducted during the year 2018 was better than the year 2017. For instance, the total rainfall for the year 2018 at Halaba was greater by 410mm than the year 2017.similarly, at Boricha during 2018 was greater by 834mm to that of 2017. While at lokaabay, the amount of rainfall was only 1.6% less than the year 2017. As presented in Figure 1, early onset of rain during 2018 and its even distribution during the growing season allowed the crop good performance.
|Year||Plant height (cm)||Ear height (cm)||BiomassY (ton/ha)||Grain Y (ton/ha)||1000 Seed weight(g)||HI|
Table 3: Mean values of plant height, ear height, above ground biomass, grain yield, thousand seed weight and harvest index response of maize varieties to conservation tillage during 2017 and 2018 cropping season.
The effect of Location on growth and yield of maize varieties
As presented in table 2, the effects of location on growth and yield of maize varieties were significant where its performance was better at Boricha and Lokaabaya than Halaba. However, the grain yield obtained at Halaba (3.96 ton) was by 8, 15and 7% higher than the national, regional and zonal productivity (3.68, 3.36, and 3.67ton ha-1), respectively (Table 4).
|Location||Plant height (cm)||Ear height (cm)||Biomass Yield (kg/ha)||Grain Y (kg/ha)||1000 Seed weight(g)||HI|
Table 4: Mean values of plant height, ear height, above ground biomass, grain yield and thousand seed weight response of maize varieties to conservation tillage across locations during 2017 and 2018 cropping season.
The effect of varieties on growth and yield of maize
Combined analysis of variance over 2017 and 2018 across locations revealed that the maize BH546 and 547 had significantly higher grain yield (5.2 and 5.0 t ha-1), but not significantly higher than the BH 540 (4.9 t ha-1). Although 016K-SPRB and 016k-SBRH gave lower yield than the hybrids, statistically expressive performance in growth across locations over years where highest plant height (208cm), ear height (108cm) with statistically similar above ground biomass with the Bako hybrids (Table 5).
|Variety||Plant height (cm)||Ear height (cm)||Biomass Yield (kg/ha)||Grain Y (kg/ha)||1000 Seed weight(g)||HI|
Table 5: Mean values of plant height, ear height, above ground biomass, grain yield and thousand seed weight response of maize varieties to conservation tillage.
The effect of location and year on growth and yield of maize varieties
Significant growth and yield variation of tested maize varieties due to the variation in location both during 2017 and 2018 (Table 6). The highest plant height(228cm), 128cm ear height, and 17.01ton ha-1 above ground biomass obtained at Borich during 2017 cropping season while the highest grain yield of 5.44-ton ha-1 was from Loka Abaya during 2018 (Table 6).
|Year X location||Plant height (cm)||Ear height (cm)||Biomass Yield (kg/ha)||Grain Yield (kg/ha)||1000 Seed eight(g)||HI|
Table 6: The effect of location and year interaction on plant height, ear height, above ground biomass, grain yield and thousand seed weight of maize varieties to conservation tillage across locations over two years (2017 and 2018).
Pearson Correlation Coefficients
The results of correlations are shown in Table 7. In this study, there was significant positive correlation between grain yield and almost all growth and yield components (plant height, ear height, above ground biomass and thousand seed weight. However, HI was not correlated with either of the parameters. These findings coincide with the results of several workers [4-7]. Plant height had positive and highly significant correlation with most of the tested characters  reported that significant positive correlation between grain yield and plant height. High correlation of grain yield with plant height is also reported by [4,8]. HI correlated significantly only with seed weight and grain yield .
|Plant height||Ear height||Biomass||Seed weight||Yield||HI|
|** = highly significant with p<0.0001|
Table 7: Pearson Correlation Coefficients for growth and yield of maize varieties tested.
The results of present study revealed that tested maize varieties exhibited superior performance at Boricha followed by Lokaabaya for growth and grain yield whereas their performance was lower at Halaba. Maize BH546 and BH547 had higher grain yield (5.2 and 5.0 t ha-1), but not significantly higher than the BH 540 (4.9 t ha-1). Although the varieties 016K-SPRB and 016k-SBRH gave lower yield than the BH varieties, statistically meaningful performance observed in growth across locations over years. The highest plant height (208cm), ear height (108cm) with statistically similar above ground biomass of the varieties 016K-SPRB and 016k-SBRH with BH546, BH547 and BH540 indicated the maize varieties not affected to conservation tillage rather the tested materials showed adaptive performance for further study under the tillage system.