Oscar Koech | University of Nairobi, Kenya (original) (raw)

Papers by Oscar Koech

This study evaluated water use efficiency (WUE) of six range grasses, namely; Chloris roxburghian... more This study evaluated water use efficiency (WUE) of six range grasses, namely; Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense grown at 80, 50, 30% field capacity (FC) soil moisture contents and rainfed treatment which represented water deficit conditions. The changes in soil moisture content were measured by Gypsum Block which aided in determining the irrigation schedules. The grasses demonstrated varied levels of WUE which was evaluated by amount of biomass productivity in relation to evapotranspired water during the growing period. The three soil moisture content treatments had higher water use efficiency than rainfed conditions. There was a declining trend in WUE with grass species maturity where S. sudanense had higher WUE at 8, 10 and 12th weeks (> 15 kg DM ha-1 mm-) in all the treatments followed by C. gayana and E. macrostachyus and were significantly (p<0.05) different from E. superba, C. ciliaris and C. roxburghiana which had WUE less than 10 among the six grass species. The 30% FC soil moisture content had higher WUE at all the phenological stages for S. sudanense, C. gayana and E. macrostachyus compared to 80, 50% FC and rainfed with all having WUE greater than 20 kg DM ha-1 mm-1. These three species are recommended for irrigated pasture establishment in semi-arid lands where water supply uncertainties exist, owing to their high water use efficiency under lower soil moisture levels.

This study evaluated six grass species in terms of water stress responses by visual quality and l... more This study evaluated six grass species in terms of water stress responses by visual quality and living ground cover attributes and the recovery responses post water stress grown at 80, 50, 30% field capacity soil moisture contents. The grass species evaluated were Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense. The grasses demonstrated varied levels of water stress tolerance as evaluated by quality ratings based on colour (greenness) and uniformity of colour, leaf firing, living matter and wilting signs. All species declined in visual quality rating with prolonged water stress treatment with exception of Sorghum sudanense and Cenchrus ciliaris that had better quality ratings of six after 42 days water stress period. Sorghum sudanense, Chloris gayana and Cenchrus ciliaris had accelerated recovery in quality, attaining a visual rating of eight at 21 days of water stress period. The three soil moisture content treatments had higher quality ratings than rainfed conditions which represented water deficit. Sorghum sudanense and Chloris gayana had higher quality ratings and water use efficiency under rainfed compared to the other species. All the grasses showed higher living ground cover greater than 40% at recovery period of 28 days, when irrigation was resumed at the prescribed level, and attained living cover of over 60% by day 42. Sorghum sudanense, Chloris gayana and Cenchrus ciliaris were able to withstand water stress longer and had also a quick recovery among the six grasses. These three species are recommended for pasture establishment in semi-arid lands where water supply uncertainties exist, owing to their high tolerance to water stress.

Seed quality and effects of storage on viability of six range grass species grown at 80, 50 and 3... more Seed quality and effects of storage on viability of six range grass species grown at 80, 50 and 30% Field capacity soil water content and rain fed were evaluated. Freshly harvested seeds at week 2 from date of harvest (DOH) had the lowest percent germination. Enteropogon macrostachyus showed low GP (<10%) after 2 weeks storage but at the late incubation periods of 11 th to 14 th day. Sorghum sudanense showed higher GP (> 50%) after storage period of 2 weeks from DOH and GP>75% from the three soil water content after storage period of 36 weeks. The results also showed after storage periods of 12 weeks, all the grass species start to germination after day 3 of incubation, unlike in the freshly harvested-2 weeks storage period where germination starts after 7 days of incubation except for Sorghum sudanense. Germination index (GI) increased with storage periods for all the grass species with Sorghum sudanense having the highest GI of over 20 after 12 weeks of storage. Storage period of 12 weeks increases seed viability of the six grasses and Sorghum sudanense has higher seed viability even when freshly harvested compared to the other species.

Seed yields of six range grass species grown at 80, 50 and 30% field capacity (FC) soil moisture ... more Seed yields of six range grass species grown at 80, 50 and 30% field capacity (FC) soil moisture content and rain fed condition were evaluated. The grasses included Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana and Sorghum sudanense (Sudan grass). Watered treatments had higher seed yields compared to rain fed for all the grasses. Chloris roxburghiana had higher seed yields at 50 and 30 % FC (516.1 and 633.4 kg ha-1 , respectively), and lower yields at 80% FC and rain fed treatment (103 and 54.3 kg ha-1 , respectively). Eragrostis superba and Enteropogon macrostachyus showed no difference in seed yields across watered. Cenchrus ciliaris had no significant difference among watered and rain fed. Chloris gayana produced higher seed yields at 30% FC (1066.8 kg ha-1) while 80 and 50% FC and rain fed having 766.9, 866.8 and 123.7 kg ha-1 , respectively. The highest yield was observed in Sorghum sudanense at 80% FC and was different (p≤0.05) from the others (1250 kg ha-1), with 50, 30% FC and rain fed having 700.5, 533.9 and 150.7 kg ha-1 , respectively. Sorghum sudanense was highest yielder under rain fed (150.7 kg ha-1) with least being Cenchrus ciliaris (21.8 kg ha-1). Chloris gayana and Sorghum sudanense have demonstrated potential higher seed yielders under lower moisture supply.

Introduction: Rangelands are important source of pasture for livestock in Kenya since time immemo... more Introduction: Rangelands are important source of pasture for livestock in Kenya since time immemorial to pastoral households. However, seasonality on forage availability has been a big challenge in meeting animals' feed requirements. This demands harvest and storage of pastures for use during dry seasons. Hay making has been done to bridge this forage deficit periods. However, hay quality in the rangelands is affected by curing methods, phonological stage at harvest, and the storage duration. We therefore evaluated the effect of field curing and storage duration on the quality (Crude Protein (CP)) of hay from six rangeland grasses in Kenya. Methods: The grasses evaluated are Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense. These grasses are the common species in the rangelands of Kenya and have been promoted in the past for hay making and reseeding interventions. The grasses were harvested at the mature flowering stage (12 weeks phenological stage), which is a period that provides high biomass without much effect on quality as practiced in the study area. The grasses were then cured in the field for 1, 2, and 3 days before baling and stored indoors for 12, 24, and 36 weeks. Samples were taken for CP content determination at the three periods following Macro-Kjeldahl Method.

This study evaluated water use efficiency (WUE) of six range grasses, namely; Chloris roxburghian... more This study evaluated water use efficiency (WUE) of six range grasses, namely; Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense grown at 80, 50, 30% field capacity (FC) soil moisture contents and rainfed treatment which represented water deficit conditions. The changes in soil moisture content were measured by Gypsum Block which aided in determining the irrigation schedules. The grasses demonstrated varied levels of WUE which was evaluated by amount of biomass productivity in relation to evapotranspired water during the growing period. The three soil moisture content treatments had higher water use efficiency than rainfed conditions. There was a declining trend in WUE with grass species maturity where S. sudanense had higher WUE at 8, 10 and 12th weeks (> 15 kg DM ha-1 mm-) in all the treatments followed by C. gayana and E. macrostachyus and were significantly (p<0.05) different from E. superba, C. ciliaris and C. roxburghiana which had WUE less than 10 among the six grass species. The 30% FC soil moisture content had higher WUE at all the phenological stages for S. sudanense, C. gayana and E. macrostachyus compared to 80, 50% FC and rainfed with all having WUE greater than 20 kg DM ha-1 mm-1. These three species are recommended for irrigated pasture establishment in semi-arid lands where water supply uncertainties exist, owing to their high water use efficiency under lower soil moisture levels.

This study evaluated six grass species in terms of water stress responses by visual quality and l... more This study evaluated six grass species in terms of water stress responses by visual quality and living ground cover attributes and the recovery responses post water stress grown at 80, 50, 30% field capacity soil moisture contents. The grass species evaluated were Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense. The grasses demonstrated varied levels of water stress tolerance as evaluated by quality ratings based on colour (greenness) and uniformity of colour, leaf firing, living matter and wilting signs. All species declined in visual quality rating with prolonged water stress treatment with exception of Sorghum sudanense and Cenchrus ciliaris that had better quality ratings of six after 42 days water stress period. Sorghum sudanense, Chloris gayana and Cenchrus ciliaris had accelerated recovery in quality, attaining a visual rating of eight at 21 days of water stress period. The three soil moisture content treatments had higher quality ratings than rainfed conditions which represented water deficit. Sorghum sudanense and Chloris gayana had higher quality ratings and water use efficiency under rainfed compared to the other species. All the grasses showed higher living ground cover greater than 40% at recovery period of 28 days, when irrigation was resumed at the prescribed level, and attained living cover of over 60% by day 42. Sorghum sudanense, Chloris gayana and Cenchrus ciliaris were able to withstand water stress longer and had also a quick recovery among the six grasses. These three species are recommended for pasture establishment in semi-arid lands where water supply uncertainties exist, owing to their high tolerance to water stress.

Seed quality and effects of storage on viability of six range grass species grown at 80, 50 and 3... more Seed quality and effects of storage on viability of six range grass species grown at 80, 50 and 30% Field capacity soil water content and rain fed were evaluated. Freshly harvested seeds at week 2 from date of harvest (DOH) had the lowest percent germination. Enteropogon macrostachyus showed low GP (<10%) after 2 weeks storage but at the late incubation periods of 11 th to 14 th day. Sorghum sudanense showed higher GP (> 50%) after storage period of 2 weeks from DOH and GP>75% from the three soil water content after storage period of 36 weeks. The results also showed after storage periods of 12 weeks, all the grass species start to germination after day 3 of incubation, unlike in the freshly harvested-2 weeks storage period where germination starts after 7 days of incubation except for Sorghum sudanense. Germination index (GI) increased with storage periods for all the grass species with Sorghum sudanense having the highest GI of over 20 after 12 weeks of storage. Storage period of 12 weeks increases seed viability of the six grasses and Sorghum sudanense has higher seed viability even when freshly harvested compared to the other species.

Seed yields of six range grass species grown at 80, 50 and 30% field capacity (FC) soil moisture ... more Seed yields of six range grass species grown at 80, 50 and 30% field capacity (FC) soil moisture content and rain fed condition were evaluated. The grasses included Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana and Sorghum sudanense (Sudan grass). Watered treatments had higher seed yields compared to rain fed for all the grasses. Chloris roxburghiana had higher seed yields at 50 and 30 % FC (516.1 and 633.4 kg ha-1 , respectively), and lower yields at 80% FC and rain fed treatment (103 and 54.3 kg ha-1 , respectively). Eragrostis superba and Enteropogon macrostachyus showed no difference in seed yields across watered. Cenchrus ciliaris had no significant difference among watered and rain fed. Chloris gayana produced higher seed yields at 30% FC (1066.8 kg ha-1) while 80 and 50% FC and rain fed having 766.9, 866.8 and 123.7 kg ha-1 , respectively. The highest yield was observed in Sorghum sudanense at 80% FC and was different (p≤0.05) from the others (1250 kg ha-1), with 50, 30% FC and rain fed having 700.5, 533.9 and 150.7 kg ha-1 , respectively. Sorghum sudanense was highest yielder under rain fed (150.7 kg ha-1) with least being Cenchrus ciliaris (21.8 kg ha-1). Chloris gayana and Sorghum sudanense have demonstrated potential higher seed yielders under lower moisture supply.

Introduction: Rangelands are important source of pasture for livestock in Kenya since time immemo... more Introduction: Rangelands are important source of pasture for livestock in Kenya since time immemorial to pastoral households. However, seasonality on forage availability has been a big challenge in meeting animals' feed requirements. This demands harvest and storage of pastures for use during dry seasons. Hay making has been done to bridge this forage deficit periods. However, hay quality in the rangelands is affected by curing methods, phonological stage at harvest, and the storage duration. We therefore evaluated the effect of field curing and storage duration on the quality (Crude Protein (CP)) of hay from six rangeland grasses in Kenya. Methods: The grasses evaluated are Chloris roxburghiana, Eragrostis superba, Enteropogon macrostachyus, Cenchrus ciliaris, Chloris gayana, and Sorghum sudanense. These grasses are the common species in the rangelands of Kenya and have been promoted in the past for hay making and reseeding interventions. The grasses were harvested at the mature flowering stage (12 weeks phenological stage), which is a period that provides high biomass without much effect on quality as practiced in the study area. The grasses were then cured in the field for 1, 2, and 3 days before baling and stored indoors for 12, 24, and 36 weeks. Samples were taken for CP content determination at the three periods following Macro-Kjeldahl Method.