Enhancing phosphorus availability in some phosphate fixing soils of the Transkei region, South Africa using goat manure

Low availability of soil phosphorus (P) caused by strong sorption of P is a major constraint to agricultural production in most South African soils, particularly those from the high rainfall areas. The aim of this study was therefore to investigate whether combined addition of goat manure with inorganic P fertilizers could enhance P availability in some P fixing soils of the Transkei region, South Africa. The study addressed the following specific objectives (i) to assess P sorption capacities and requirements of selected soils and their relationship with selected soil properties and single point sorption test, (ii) to assess the effects of goat manure and lime addition on P sorption properties of selected P fixing soils (iii) to assess the temporal changes in concentration of inorganic and microbial biomass P fractions following application of inorganic fertilizer P with goat manure in a laboratory incubation experiment, and, (iv) to assess the effects of goat manure application with inorganic phosphate on inorganic and microbial biomass P fractions, P uptake and dry matter yield of maize. Sorption maxima (Smax) of seven soils examined ranged from 192.3 to 909.1 (mg P kg-1) and were highly and positively correlated with sorption affinity constant (r = 0.93, p = 0.01) and organic C (r = 0.71, p = 0.01). The amount of P required for maintaining a soil solution concentration of 0.2 mg P l-1 ranged from 2.1 to 123.5 mg P kg-1 soil. Soils collected from Qweqwe (a Cambisol), Qunu (an Acrisol), Ncihane (a Luvisol) and Bethania (a Ferralsol) had lower external P requirement values and were classified as lower sorbers, whereas soils from Ntlonyana (a Planosol), Chevy Chase (a Ferralsol) and Flagstaff (a Ferralsol) were classified as moderate sorbers. The results suggested that P availability could be compromised in 43 percent iii of the soils studied and that measures to mitigate the adverse effects of P sorption were needed to ensure that P is not a limiting factor to crop production, where such soils are found. Goat manure addition at varying rates (5, 10 and 20 tha-1 dry weight basis) to two of the moderately P fixing soils from Chevy Chase and Flagstaff, reduced P sorption maxima (Smax) compared to the control treatment. Phosphate sorption decreased with increasing amounts of goat manure in both soils but the extent of reduction was greater on Chevy Chase soil than on Flagstaff soil. The relative liming effects of the different rates of goat manure followed the order 20 t GM ha-1 > 10 t GM ha-1 > 5 t GM ha-1. In a separate experiment, addition of inorganic P at varying rates (0, 90, 180, and 360 kg P ha-1) to Flagstaff soil increased labile P fractions (resin P, biomass P and NaHCO3-Pi) and the increases were greater when goat manure was co-applied. The control treatments contained only 17.2 and 27.5 mg P kg-1 of resin extractable P in the un-amended and manure amended treatments, respectively which increased to 118.2 and 122.7 mg P kg-1 on day 28 of incubation. Biomass P concentration was increased from 16.8 to 43.9 mg P kg-1 in P alone treatments but the fraction was greatly enhanced with manure addition, increasing it from 32.6 to 97.7 mg P kg-1. NaOH-Pi was the largest extractable Pi fraction and ranged from 144.3 to 250.6 mg P kg-1 and 107.5 to 213.2 mg P kg-1 in the unamended and manure amended treatments, respectively. Dry matter yield and P uptake by maize grown in the glasshouse were highly and significantly (p = 0.05) correlated with the different P fractions in the soil. The correlations followed the order resin P (r = 0.85) > NaOH-Pi (r = 0.85) > NaHCO3-Pi (r = 0.84) >> biomass P (r = 0.56) for dry matter yield at 6 weeks after planting. At 12 weeks after planting, goat manure had iv highly significant effects on resin P and biomass P but had no effect on NaHCO3-Pi and NaOH–Pi. The combination of biomass P, resin P and NaHCO3-Pi explained 75.8 percent of the variation in dry matter yield of which 63.0 percent of the variation was explained by biomass P alone. The greatest increase in biomass P occurred when added P was co-applied with 5 or 10 tha-1 goat manure. The predictive equation for maize dry matter yield (DM) was: DM (g) = 1.897 biomass P + 0.645 resin P (r = 0.73). Resin P was the fraction that was most depleted due to plant uptake and decreased by 56 to 68 percent between the 6th week and the 12th week of sampling indicating that it played a greater role in supplying plant available P. The results therefore suggested that the use of goat manure may allow resource poor farmers to use lower levels of commercial phosphate fertilizers because of its effect to reduce soil P sorption. In addition, higher increases in biomass P due to manure addition observed at lower rates of added P indicated that goat manure has potential for enhancing bioavailability and fertilizer use efficiency of small inorganic P applications

Climate Smart \u3ci\u3eUrochloa\u3c/i\u3e Grasses Improves Soil Health in the Semi-Arid Tropics of Kenya

The measurement of soil aggregates stability and soil microbial biomass can be used as an early indicator of long-term changes in soil quality. A study was conducted to quantify the amounts of shoots and roots biomass of Urochloa grass cultivars (commonly known as Brachiaria) and their effects on changes in the size distribution and stability of soil aggregates and on microbial biomass carbon (C), nitrogen (N) and phosphorus (P) in a structurally unstable sandy loam soil at Ithookwe and Katumani in semi-arid tropical Kenya. The Urochloa grass cultivars included Urochloa decumbens cv. Basilisk, U. brizantha cvs Marandu, MG-4, Piatã and Xaraes, U. humidicola cv. Llanero and U. hybrid cv. Mulato II. Rhodes and Napier grass were included in the treatments as controls. Roots biomass was evaluated using the soil-coring method to depths of 0 – 15 and 15 – 30 cm. Four aggregates-size fractions (\u3e 2000 μm, 250 – 2000 μm, 53 – 250 μm, and \u3c 53 μm) were isolated using the wet sieving method. Microbial biomass C, N and P were determined on field moist rhizosphere soil (18 - 23% by weight) from a depth of 10 cm using the chloroform fumigation-extraction technique. Shoots biomass of the Urochloa cultivars ranged from 3.0 to 11.3 t ha-1 and 5.5 to 8.3 t ha-1 at Ithookwe and Katumani sites respectively. Marandu, Xaraes, Basilisk and Piata had higher roots biomass than the controls (Rhodes grass and Napier grass). Aggregate stability differed among the grasses and was highest in soils under Mulato II and Marandu with mean weight diameters of 4.49 and 4.31 mm, respectively. Generally, microbial biomass N was higher in plots with grasses than in the bare plots. Among Urochloa cultivars, the highest microbial biomass C was recorded in plots with Mulato II and the lowest from the plots with MG-4

Accelerate Scaling up Forage Intensification Using Novel Digital Extension Approach in Kenya

Wide scale adoption of diverse forages improves livestock productivity and farmers welfare. However, limited access to information and knowledge on forage production results in slow adoption in Kenya. There is need to enhance information and knowledge exchange among farming communities for efficient and effective adoption and decision-making. An inter-institutional pilot project was initiated in 2017 to scale-up forages in Kenya using a novel extension approach - the village knowledge centre (VKC). A VKC is an information and communication technology (ICT) digital platform-based linking farmers through smart phones and social media as a conduit for faster and effective information and knowledge. This paper shares the experiences of VKC intervention to scale up Urochloa grass technology among smallholder farmers for livestock productivity. Through the VKC support there has been increased access of information and knowledge on Urochloa grass management, conservation and livestock feeding. Approximately 702 farmers out of which 28% were women visited the VKC to seek information on Urochloa grass from May 2018 to May 2020. It has trained 22 lead farmers on the establishment and management of Urochloa grass. The VKC has created two WhatsApp groups for networking among farmers with over 330 members. Between September 2018 and May 2020, the groups shared 2550 messages on Urochloa management, conservation, and livestock feeding with other farmers in their communities. Additionally, the VKC has improved availability of Urochloa grass seeds to farmers. Over 530 farmers received the seeds through the VKC, while 500 made request though mobile phone Short Message Services (SMS) and were supplied using courier services. It was evident that VKC intervention has not only improved the adoption rate, but also led to increased forage productivity and higher income for farmers. There is a need to continue using tools such as the VKC in the dissemination of information on Urochloa grass and explore suitable funding for sustainability of the centre after the end of the project

Participatory Evaluation and Selection of Improved \u3ci\u3eUrochloa\u3c/i\u3e Grass Cultivars in Kenya

Low adoption of superior agricultural technologies has been attributed to insufficient attention given to farmers’ priorities and perceptions while developing technologies. There is therefore a need to involve farmers in development of new forage technologies in order to increase adoption. Participatory variety selection (PVS) was conducted on eight Urochloa grass cultivars in the coastal lowlands, eastern midlands, central highlands and northwestern highlands of Kenya to select cultivars that are more adaptable in each region. The eight Urochloa cultivars; U. brizantha cvs. Marandu, Xaraes, Piatã, MG4, U. decumbens cv. Basilisk, U. humidicola cvs. Llanero and Humidicola, and U. hybrid cv. Mulato II were evaluated against cultivated local grasses; Rhodes grass (Chloris gayana cv. KATR3) and Napier grass (Pennisetum purpureum cv. Kakamega 1). In each region, farmers were engaged in development of selection criteria through focus group discussions. For each criterion, farmers’ scored on individual grass cultivars using a Likert scale of 1 to 4 with higher scores indicating high cultivar preference. Farmers considered 12 to17 plant attributes in the selection of the most suitable forages for planting. The attributes included plant height, colour, spread, biomass among others. MG4 was the most preferred Urochloa cultivar in eastern midlands, central and northwestern highlands while Mulato II was most preferred in coastal lowlands. The study concluded that, the selected Urochloa cultivars met the farmers’ needs and were advanced for on-farm testing and evaluation for livestock benefits

PLANT SHOOTS AND ROOTS BIOMASS OF BRACHIARIA GRASSES AND THEIR EFFECTS ON SOIL CARBON IN THE SEMI-ARID TROPICS OF KENYA

Grassland management practices that improve carbon uptake by increasing productivity or reducing carbon losses can lead to net accumulation of carbon in soils. A study was conducted to quantify the amounts of shoots and roots biomass of Brachiaria grass cultivars and their effects on soil carbon in two sites, Ithookwe and Katumani in semi-arid tropical Kenya. The grass cultivars were Brachiaria decumbens cv. Basilisk, B. brizantha cvs. Marandu, MG4, Piatã and Xaraes, B. humidicola cv. Llanero and B. hybrid cv. Mulato II. These were compared with two locally cultivated grasses (Chloris gayana cv. KAT R3 and Pennisetum purpureum cv. Kakamega 1). The grass treatments were evaluated with fertilizer application (40 kg P applied at sowing and 50 kg N ha-1 in each wet season) and with no fertilizer application. Shoots biomass of the Brachiaria cultivars ranged from 3.0 to 11.3 t ha-1 and 5.5 to 8.3 t ha-1 at Ithookwe and Katumani sites respectively in year 1. The highest shoots biomass recorded at Ithookwe was from cv. Piata while cv. MG4 gave the highest biomass at Katumani. Similar trends were recorded in year 2 of growth though the shoots biomass was lower at Katumani. However, the yields were significantly lower than those recorded from control, Napier grass in both years. The cv. Marandu, Xaraes, Basilisk and Piata had higher roots biomass than the controls (Rhodes grass and Napier grass) indicating greater potential for the Brachiaria grasses to sequester more carbon in the soil. The results of this study indicate that introduction of Brachiaria grasses in the semi-arid tropics of Kenya and in other similar environments can help increase soil carbon stocks that would mitigate the adverse effects of climate change and have greater economic returns

Soil Microbial Carbon, Nitrate and Ammonium Nitrogen Dynamics in \u3ci\u3eUrochloa\u3c/i\u3e Grass Cultivated in Sub-Humid Kenya

A study was conducted to monitor the dynamics of available soil phosphorus (P), soil microbial biomass carbon (SMBC), nitrogen (SMBN), ammonium and nitrate nitrogen under seven Urochloa grass cultivars at Kitale, Kenya. The Urochloa cultivars: Urochloa brizantha cvs. Marandu, MG-4, Piata, Xaraes, U. decumbens cv. Basilisk, U. hybrid cv. Mulato II and U. humidicola cv. Llanero was compared with two popularly grown forages, Rhodes grass (Chloris gayana cv. KAT R3), Napier grass (Pennisetum purpureum cv. KK1) and annual weeds. The treatments were tested in a randomized complete block design arranged in a split plot treatment structure with two rates of fertilizer N (0 and 100 kg N ha-1yr-1) and P (0 and 40 kg P ha-1) assigned to the main plots and the grass cultivars assigned to the subplots. After 80 weeks, moist rhizosphere soil was sampled at 0 – 10 cm depth to determine microbial biomass. Application of fertilizer N and P did not significantly (P \u3e 0.05) influence SMBC, SMBN, ammonium N (NH4+N) and nitrate N (NO3-N). However, significant (P = 0.001) changes in soil properties, including NH4+N and NO3-N due to grass cultivars, were observed. After 80 weeks, the bare plot, annual weeds and Napier grass accumulated higher pools of ammonium and nitrate N, but the microbial biomass (SMBC and SMBN) in these treatments were lower than in Urochloa grasses. Soil pH was also low, while NO3-N was high indicating increased nitrification in the bare and Napier grass plots. Ammonium N was the most dominant form of inorganic N in Llanero and Piata due to increased plant uptake or reduced nitrification rates. The results suggested that the change in the SMBC and SMBN in the Urochloa grasses was regulated by the nitrate and ammonium N and soil pH

Identification of Niches for Integration of Brachiaria Grasses in Smallholder Mixed Crop-Livestock Farming Systems in Kenya

Inadequate quantity and quality of feed is the major constraint to livestock productivity in Kenya. Low rainfall, lack of adapted forages and poor management of sown forages are major factors that affect feed resources production. In most of the farming systems, forages are relegated to the less fertile and degraded soils resulting into poor growth. As a result the growth is poor resulting in deficient in minerals content, low crude protein (CP) and energy. The situation in exacerbated by climate variability and frequent drought. On the other hand, feed resources derived from crop residues, particularly cereals are of poor quality and not sufficient to meet animal production (Njarui and Mureithi, 2006). A research programme was initiated in 2012 to explore superior feed resources and increase availability of high quality forages to increase livestock productivity in East Africa. The program focuses on evaluation of drought and marginal soil adapted improved Brachiaria cultivars from South America. The genus Brachiaria is predominantly an African grass with about 100 species. The Brachiaria grasses are the most widely grown forages in South America (Miles et al., 2004). These grasses produce high biomass, enhance soil fertility and reduce greenhouse gas emission (Peters et al., 2012), are highly nutritious and are known to increase milk (Njarui, pers. comm.) thus suitable for different farming systems of Kenya. However, before integration of these grasses into farming systems, it was imperative to identify suitable niches suitable for growing these grasses. The knowledge gained from the study will facilitate development of suitable approaches for promoting these grasses across diverse production systems of Kenya

Climate-Smart \u3cem\u3eBrachiaria\u3c/em\u3e for Improving Livestock Production in East Africa: Emerging Opportunities

Brachiaria grass is an important tropical forage of African origin with desirable attributes of agricultural and environmental significance. Brachiaria has been extensively cultivated as a pasture across the tropics except in its endemic provenance of Africa. In 2013, a collaborative research program was initiated in Kenya and Rwanda with the aim of improving the availability of quality livestock feeds adapted to drought and low fertility soils using Brachiaria. The outcomes sought were increased livestock productivity leading to improved farmer income and the development of seed production opportunities. The program has identified five preferred cultivars, and four of them are currently being evaluated on-farm by over 2000 small-holder farmers in Kenya and Rwanda for livestock productivity. Preliminary milk production data has shown a 15 to 40% increase in milk production in Kenya and an average increase of 36% in Rwanda. The substitution of Napier grass by Brachiaria in the feed has increased average daily body weight gain of cattle by 205g during a 12 week period. Kenyan farmers reported increased on-farm forage availability by three months after Brachiaria introduction. The program has also worked to determine the role of endophytes and plant associated microbes for the improvement of biomass production and adaptation of Brachiaria to biotic and abiotic stresses. A diverse group of fungi and bacteria were isolated, identified and characterized, and the role of these microbes on plant growth and plant pathogen suppression is being investigated. This paper discusses the rationale for selecting Brachiaria as potential forage for eastern Africa and highlights current achievements, and identifies areas for future research