Utilization and management practices of animal manure for replenishing soil fertility among smallscale crop farmers in semi-arid farming districts of the North West Province,South Africa

Poor soil fertility is one of the most limiting biophysical factors to agricultural production among smallscale farmers in much of the sub-Saharan Africa, especially the semi-arid areas. In this study, a survey of 200 randomly selected farming households across four districts (Mafikeng, Ditsobotla, Ganyesa and Taung) located in a semi-arid environment of the North West Province in South Africa was conducted to establish the utilisation and management of animal manure for managing soil fertility. The results showed that 66% of the farmers across the districts used animal manure on their crops. The types of manure used were in the order cattle > sheep = goat > chicken. Cattle manure was readily available from farmers’ own kraal or neighbours. Despite its availability and advantages, chicken manure was seldom used. The rates of manure application were generally low (mean 2.5 tha⁻¹) although most farmers (71%) applied it annually. In the majority of cases, manure would be applied to about half (57.5%) of the cropped land every year (average farm size was 5.3 hectares). The manure was mostly broadcasted (76%) on the surface before being ploughed under followed by dollop (53%). The quality of most of the manure resources was relatively poor as it had low N and P but high soil content (mean 22.7%). The study found that farmers have developed local knowledge with regards to criteria for defining manure quality. The criterion, which used physical characteristics such as colour, moisture content and presence of moulds in the manure, was quite consistent across the study districts and points to the possibility of the indigenous knowledge being interfaced with scientific knowledge. The factors which positively influenced farmers’ decision to use manure were herd sizes, farming experience, training and availability of manure, extension services and labour. On the other hand, farm sizes negatively affected manure use. It was observed that housing, feeding, storage and handling practices of manure resources was not optimum in most of the study districts and this contributed to loss of nutrients and quality. It is recommended that improved strategies of manure production and handling be adopted by farmers in order to maximise the quality and efficiency of manure utilization. The potential that exists in using chicken manure to supply crop nutrients needs to be explored.     

Factors influencing manure application by farmers in semi-arid west Africa

Animal manure is one of the principal sources of nutrients for soil fertility maintenance and crop production in semi-arid west Africa. Farm-level decisions concerning the use of manure are governed by socioeconomic and institutional factors, as much as they are by agronomic and ecological concerns. This paper analyses the cultural and socioeconomic factors affecting manure use decisions in parts of semi-arid West Africa using a logit model. The results show that the major factors that positively influence farmers' manuring decisions are the farmer's own herd size, contractual arrangements between herders and farmers for manure, seasonal migration and its effect on livestock investment and the proportion of cultivated land owned by the farmer. Factors found to negatively affect manure use are farm size, distance of fields to the homestead, the proportion of cultivated land recently under fallow and land-labour ratio. The paper concludes by suggesting strategies for removing the constraints to efficient manure utilisation and soil fertility improvement in semi-arid West Africa.     

Factors affecting the adoption of fertilizers by rice farmers in Côte d'Ivoire

This paper analyzed the factors that affect the adoption of chemical fertilizers by rice farmers in Côte d'Ivoire using a Tobit model. The results show that the major factors that positively influence farmers' use of fertilizers in rice fields are cultivation of lowlands, use of mechanization, farm size, land pressure and availability of non-farm income. Factors found to negatively affect the use of fertilizer in rice fields are the distance of the field to the village, distance of the village to the major market, and if the cultivator is a female. The paper concludes with strategies for targeting soil fertility interventions on farmers' rice fields.     

Farmers' perceptions and attitudes towards introduced soil-fertility enhancing technologies in western Africa

Soil fertility enhancing technologies (SFETs) have been promoted in the West African Semi-Arid Tropics (WASAT) for many years with limited success. Using a qualitative approach of focus group discussions, long, open-ended interviews and observations from field visits, this paper explores with farmers their beliefs and rationales behind the adoption or non-adoption of SFETs. Farmers are knowledgeable about, and practise SFETs of rock phosphate application, crop residue and farm yard manure, chemical fertilizer and crop rotation to combat soil fertility decline. Their attitudes to and rationales behind adoption decisions are influenced by the availability and use policies of land and labour resources, food security concerns, perceived profitability, contribution to sustainability and access to information. Some of the factors are beyond farmers' control and require a broad and integrated effort from research, extension and government to promote the use of the SFETs in the region.     

Management of organic matter in the tropics: translating theory into practice

Inputs of organic materials play a central role in the productivity of many tropical farming systems by providing nutrients through decomposition and substrate for synthesis of soil organic matter (SOM). The organic inputs in many tropical farming systems such as crop residues, manures, and natural fallows are currently of low quality and insufficient quantity to maintain soil fertility hence there is need to find alternative or supplementary sources of nutrients. Knowledge gained over the past decade on the role of organic resource quality in influencing soil nutrient availability patterns (Synchrony Principle) and SOM maintenance (SOM Principle) provides a strong scientific basis on which to develop management tools. This scientific information must be linked with farmer knowledge and circumstances to provide a realistic approach to soil fertility and SOM management in the tropics. A decision tree has been developed for testing hypotheses about the resource quality parameters that affect nitrogen release patterns and rates. The decision tree is linked to an Organic Resource Database (ORD) with detailed information on the resource quality of agroforestry trees and leguminous cover crops providing a systematic means of selecting organic resources for soil fertility management. The decision tree has also been translated into a practical field guide for use with farmers in evaluating organic materials. The longer-term effects of organic inputs on SOM might also be addressed through the decision tree and database. It is generally believed that materials good for short-term soil fertility will not build or maintain SOM; if true then it is difficult to imagine practical means of maintaining SOM in the African context where short-term fertility issues will take precedence over longer-term maintenance of SOM. This revised version was published online in June 2006 with corrections to the Cover Date.     

Developments in soil phosphorus status in a recently reclaimed polder in the Netherlands

Compliance with current phosphorus (P) fertilization recommendations would ultimately result in a soil P status of agricultural land in the agronomical optimal range. In practice though there are large variations in soil P status among farms and fields. Our study aimed at increasing the understanding of the cause-effect relationships for these spatial variations in soil P test values. The Northeast Polder in The Netherlands was chosen as study area, because of its characteristics. It was reclaimed from the sea in 1942, has one major soil type (calcareous loam), well-educated farmers, one dominant land use (arable farming) and little pressure to use animal manure. We tested the hypothesis that in this polder mean P status has developed towards the optimal range with a small standard deviation. We analysed available soil P analyses records (>30,000) from the period ~1950?C2004, and conducted a questionnaire about fertilization practices among farmers. The soil P(w) values increased steadily and significantly from the agronomical range ??low?? to ??ample sufficient?? from 1971 to 2004. Variation within and between farms also increased. About 45?% of the farmers appear to aim at a soil P status above the agronomical optimal range, and >70?% of the farmers indicated that they are uncertain whether the obtained increase in soil P(w) status is actually plant available P. In conclusion, our hypothesis was rejected: for farmers in our study area, risk avoidance seems the decisive factor for pursuing a soil P status above the agronomical optimal range. If even well-educated farmers question the official fertilizer recommendations and aim at higher levels of soil P fertility, also other farmers worldwide may continue to aim such supra-optimal soil P status. This is undesirable given the diminishing P resources. Possible solutions could be to define more refined P fertilization recommendations and better and more intensified communication of those recommendations to farmers and their advisers.     

The role of fertilizers in sustaining agriculture in sub-Saharan Africa

African farmers have relied traditionally on fallowing for up to 15 years to restore soil fertility. Leaving land unproductive for such periods is a luxury many regions cannot afford, given the contemporary decline in per capita food production (1%/year). Thus, alternative soil fertility maintenance measures such as agroforestry, novel intercropping systems, residue conservation, the use of manure, soil amendments, and fertilizer have recently been given greater emphasis. The Food and Agriculture Organization (FAO) estimates that 75% of the increase in regional food production must come from intensive production. However, fertilizer use in sub-Saharan Africa is only one tenth of the world average. The small size of fertilizer markets in most countries is an important contributing factor in relatively high farm-gate prices and low fertilizer use. There is significant scope for improving the efficiency of fertilizer procurement and distribution in the region. Most countries can substantially reduce farm-gate prices by changing to higher analysis formulas, relaxing specifications, importing in bulk and bagging locally, and improving systems of distribution. Various options of fertilizer production are discussed in this context. Intensification in areas where environmental constraints are limited and surplus production can be marketed may alleviate the demographic pressures to cultivate marginal land where increased land and labor productivity is unlikely. Although substantial effort should be made to research sustainable farming system options for marginal lands, efforts in the more resilient environments should concentrate on increased crop production, using inputs where feasible. Provisions should be made for adequate support in the infrastructural, institutional, and policy spheres to transform these regions into granaries.     

Managing soil fertility diversity to enhance resource use efficiencies in smallholder farming systems: a case from Murewa District,Zimbabwe

Smallholder farms in sub-Saharan African exhibit substantial heterogeneity in soil fertility, and nutrient resource allocation strategies that address this variability are required to increase nutrient use efficiencies. We applied the Field-scale resource Interactions, use Efficiencies and Long-term soil fertility Development (FIELD) model to explore consequences of various manure and fertilizer application strategies on crop productivity and soil organic carbon (SOC) dynamics on farms varying in resource endowment in a case study village in Murewa District, Zimbabwe. FIELD simulated a rapid decline in SOC and maize yields when native woodlands were cleared for maize cultivation without fertilizer inputs coupled with removal of crop residues. Applications of 10 t manure ha⁻¹ year⁻¹ for 10 years were required to restore maize productivity to the yields attainable under native woodland. Long-term application of manure at 5 and 3 t ha⁻¹ resulted in SOC contents comparable to zones of high and medium soil fertility observed on farms of wealthy cattle owners. Targeting manure application to restore SOC to 50–60% of contents under native woodlands was sufficient to increase productivity to 90% of attainable yields. Short-term increases in crop productivity achieved by reallocating manure to less fertile fields were short-lived on sandy soils. Preventing degradation of the soils under intensive cultivation is difficult, particularly in low input farming systems, and attention should be paid to judicious use of the limited nutrient resources to maintain a degree of soil fertility that supports good crop response to fertilizer application.     

Factors affecting the use of fertilizers and manure by smallholders: the case of Vihiga,western Kenya

Sub-Saharan Africa faces huge food supply challenges due to increasing human population, limited opportunities to increase arable land, and declining yields associated with continuously declining soil fertility. To cater for their food requirements, smallholders use only modest levels of inorganic fertilizers and rely to a large extent on manure, which is generally of low quality. To explore factors influencing fertilizer and manure use at the farm level, 253 farm households in Vihiga district of western Kenya were sampled. A pair of Tobit models was used to relate amounts of manure and fertilizer used to household variables. The results indicate that the use of both manure and fertilizer reciprocally influence each other and are strongly influenced by household factors, and also imply that manure and fertilizer uses are endogenous. Policy changes are required to (1) reduce the burden on farming alone in rural areas; (2) promote the use of higher-cost, higher-value inputs such as fertilizers; (3) improve access to input and output markets; and (4) encourage farmer education so as to promote sustainable soil fertility management. Improved understanding of the biophysical and socioeconomic environment of smallholder systems can help target sustainable soil fertility interventions more appropriately.

Interactions of aerobically decomposed cattle manure and nitrogen fertilizer applied to soil

Inorganic N fertiliser may be applied to soil in addition to cattle manure by smallholder farmers in developing countries: (a) to complement fertilization; (b) to control a possible immobilisation of N by the manure; and (c) to eliminate the risk of yield depression due to lack of plant available N. The aim of this study was to find out if and how much N was immobilised by cattle manure, if and when remineralisation of N will take place and, if added N has an effect on decomposition of cattle manure in soil. A laboratory study was conducted applying inorganic N fertiliser to soil (NH4NO3 equivalent to 30, 60 and 120 kg N ha-1) together with four cattle manures with different C/N ratios (9–18). CO2–C mineralisation and changes of inorganic N in soil were determined over 60 d. Immobilisation of fertiliser N occurred with manure having the lowest C/N ratio but not with the manures having a higher C/N ratios. Maximum immobilization of fertiliser N (23–36%) occurred within 21 d and thereafter N was mineralised. Carbon dioxide evolution decreased in cattle manure-amended soil at increasing rates of N fertiliser, but decomposition was still higher than from the unamended control. None of the manure treated soils had significantly different contents of inorganic N after 2 months of incubation. It was not possible to use the C/N ratio of aerobically decomposed cattle manure as a tool to predict mineralization or immobilization of N. It was concluded that aerobically decomposed solid cattle manures do not contribute to the N supply of crops in the short term but can immobilize fertiliser N applied at the same time.     

Farm typologies,soil fertility variability and nutrient management in smallholder farming in Sub-Saharan Africa

Farm typologies are a useful tool to assist in unpacking and understanding the wide diversity among smallholder farms to improve targeting of crop production intensification strategies. Sustainable crop production intensification will require the development of an array of nutrient management strategies tailored to farm-specific conditions, rather than blanket recommendations across diverse farms. This study reviewed key literature on smallholder farm typologies focusing on three countries (Kenya, Malawi and Zimbabwe), to gain insights on opportunities for crop production intensification, and the importance of developing farm-specific nutrient management practices. Investigations on farm typologies have done well in highlighting the fundamental differences between farm categories, with 3–5 typologies often adequate to represent the wide differences in resource endowment. Resource-endowed farmers have ready access to large quantities of manure and mineral fertilizers, which contribute to higher soil fertility and crop productivity on their farms. Resource-constrained households use little or no manure and mineral fertilizers, and have limited capacity to invest in labour-demanding soil fertility management technologies. These farmers often have to rely on off-farm opportunities for income that are largely limited to selling unskilled labour to their resource-endowed neighbors. The variability in management practices by farmers has resulted in three main soil fertility classes that can be used for targeting soil fertility management technologies, characterized by potential response to fertilizer application as: (1) low-responsive fertile fields that receive large additions of manure and fertilizer; (2) high-responsive infertile fields that receive moderate nutrient applications; (3) poorly responsive degraded soils cultivated for many years with little or no nutrient additions. The main conclusions drawn from the review are: (1) resource constrained farmers constitute the widest band across the three countries, with many of the farmers far below the threshold for sustainable maize production intensification and lacking capacity to invest in improved seed and fertilizer, (2) farm sizes and livestock ownership were key determinants for both farmer wealth status and farm productivity, and (3) soil organic carbon and available P were good indicators for predicting previous land management, that is also invariably linked to farmer resource endowment.     

Farmer's view on soil organic matter depletion and its management in Bangladesh

Bangladesh is an agricultural country. About 80% of the total population live in rural areas. The contribution of agriculture to the gross domestic product is 30%. Rice is the major food crop while jute, sugarcane and tea are the main cash crops. Other important crops are wheat, tobacco, pulses, vegetables and fruits. Overall productivity in Bangladesh is stagnating or declining. The implication of yield stagnation or declining productivity is severe, since these trends have occurred despite rapid growth in the use of chemical fertilisers. Depletion of soil organic matter is the main cause of low productivity, which is considered one of the most serious threats to the sustainability of agriculture in Bangladesh. In Bangladesh, most soils have less than 17 g/kg and some soils have less than 10 g/kg organic matter. Farmers realise that there is a problem with soil fertility related to organic matter depletion. Farmers say that organic matter increases yield, reduces the production cost, improves crop growth and the economy, increases water-holding capacity and improves the soil structure. They recognise soil with higher organic matter content by darker brownish to black in colour. Some farmers are using fast-growing trees such as Flemingia macrophyla, Ipilipil (Leucaen leucophala), Glyricidia sepium, Boga Medula (Tephrosia candida), Dhol Kolmi (Ipomoea fistulosa), etc., as living fences, which can be used as fuel, fertiliser and fodder. To increase the soil organic matter, farmers use green manure crops, compost, quick compost, cow dung, azolla, etc. However, fuel for cooking purposes is limited and cow dung and crop residues are largely used as fuel. Crop residues are also used as fodder for livestock. Farmers expressed the wish to learn more about organic fertilizer management. However, sufficient food should be produced to keep pace with population growth. To alleviate the hunger and poverty is to increase the intensity of agricultural production and maintain favorable ecological conditions. Therefore, more organic matter should be used in the farmers' fields to sustain the soil fertility in an intensive farming system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of planting technique and amendment type on pearl millet yield, nutrient uptake, and water use on degraded land in Niger

Due to increased population pressure and limited availability of fertile land, farmers on desert fringes increasingly rely on marginal land for agricultural production, which they have learned to rehabilitate with different technologies for soils and water conservation. One such method is the indigenous zai technique used in the Sahel. It combines water harvesting and targeted application of organic amendments by the use of small pits dug into the hardened soil. To study the resource use efficiency of this technique, experiments were conducted 1999–2000, on-station at ICRISAT in Niger, and on-farm at two locations on degraded lands. On-station, the effect of application rate of millet straw and cattle manure on millet dry matter production was studied. On-farm, the effects of organic amendment type (millet straw and cattle manure, at the rate of 300 g per plant) and water harvesting (with and without water harvesting) on millet grain yield, dry matter production, and water use were studied. First, the comparison of zai vs. flat planting, both unamended, resulted in a 3- to 4-fold (in one case, even 19-fold) increase in grain yield on-farm in both years, which points to the yield effects of improved water harvesting in the zai alone. Zai improved the water use efficiency by a factor of about 2. The yields increased further with the application of organic amendments. Manure resulted in 2–68 times better grain yields than no amendment and 2–7 times better grain yields than millet straw (higher on the more degraded soils). Millet dry matter produced per unit of manure N or K was higher than that of millet straw, a tendency that was similar for all rates of application. Zai improved nutrient uptake in the range of 43–64% for N, 50–87% for P and 58–66% for K. Zai increased grain yield produced per unit N (8 vs. 5 kg kg⁻¹) and K (10 vs. 6 kg kg⁻¹) compared to flat; so is the effect of cattle manure compared to millet straw (9 vs. 4 kg kg⁻¹, and 14 vs. 3 kg kg⁻¹), respectively, Therefore zai shows a good potential for increasing agronomic efficiency and nutrient use efficiency. Increasing the rate of cattle manure application from 1 to 3 t ha⁻¹ increased the yield by 115% TDM, but increasing the manure application rate further from 3 to 5 t ha⁻¹ only gave an additional 12% yield increase, which shows that optimum application rates are around 3t ha⁻¹.     

Farmers' perceptions and management of soil organic matter – a case study from West Africa

A farm survey was carried out in 155 Ghanaian villages covering parts of the forest and savanna zones of West Africa to assess farmers' views on ‘soil organic matter’ (SOM) and its management. The results of a closed questionnaire accompanied by open discussions showed that most farmers are well aware of SOM and its importance for crop yields. In southern Ghana, farmers perceive SOM generally by its colour, while in northern Ghana, it is mostly assessed by the density and kind of vegetation. Farmers' perception of the properties of SOM was directed at its main functions as a primary provider of plant nutrients and its ability to conserve water. Other properties mentioned were the improvement of soil aeration and drainage, the loosening of soil structure as well as its impact on soil temperature. The major strategies farmers used in maintaining or augmenting SOM levels were: manure application, mulching with crop residues, slashing weeds without burning, composting, and shifting cultivation (natural fallow). Promoted technologies, such as green manuring, no tillage, or agroforestry were used only by a few of the farmers interviewed. The differences between farmers' views and strategies in the two zones as well as farmers' constraints in SOM management are discussed. It appears that the level of farmers' commitment to excellent soil management can vary with biophysical as well as socio-economic conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Appropriate technologies to replenish soil fertility in southern Africa

In southern Africa, soil nutrient reserves are being depleted because of continued nutrient mining without adequate replenishment. The consequent downward spiral of soil fertility has led to a corresponding decline in crop yields, food insecurity, food aid and environmental degradation. The central issue for improving agricultural productivity in southern Africa is how to build up and maintain soil fertility despite the low incomes of smallholder farmers and the increasing land and labour constraints they face. Under this review five main options namely: inorganic fertilizers, grain legumes, animal manures, integrated nutrient management and agroforestry options appropriate to smallholder farmers are presented. Issues addressed in the use of inorganic fertilizers are reduction in fertilizer costs, timely availability and use efficiency. Legumes can be used to diversify farm system productivity but this requires P and lime application to support better legume growth and biological nitrogen fixation (BNF) as well as development of markets for various legume products. Manure availability and quality are central issues in increasing smallholder farm productivity and increasing its efficiency through proper handling and application methods. Integrated nutrient management of soil fertility by combined application of both inputs will increase use efficiency of inputs and reduce costs and increase profitability; but the challenge is often how to raise adequate amounts of either inorganic or organic inputs. Issues such as quality of inputs, nutrient balancing, labour to collect and transport organic inputs and their management need to be optimized. These are the challenges of adoption as are the scaling up of these options to millions of small-scale farmers.     

Nitrogen dynamics following slurry injection in maize: crop development

Using pig slurry as starter fertilizer for maize (Zea mays L.), injected below the row prior to planting is a reasonable way to omit application of additional mineral fertilizer in areas with intensive animal farming. However, delayed early growth and a lack of knowledge on nutrient availability limit the interest of farmers. To extenuate farmers concerns a field trial was conducted in 2014 and 2015 to get detailed information on nitrogen (N) uptake, the subsequent influences on crop growth at different vegetative growth stages and final yield of silage maize. Besides an unfertilized control, two liquid manure injection treatments (without and with nitrification inhibitor [NI]) were compared to slurry broadcast application + mineral N and phosphorus (P) starter fertilizer at planting (MSF). In 2014, NI treatment yields increased (+16.5%) and N uptake increased (+9.6%) compared to broadcast treatment. In 2015, cold and dry conditions during early growth limited P plant availability and reduced crop growth in treatments without MSF. However, when a NI was added to the slurry prior to application, plants showed less P deficiency symptoms and better growth. At harvest no differences between the fertilized treatments were observed. In both years apparent N recovery was increased when manure was injected (48% without, and 56% with NI, respectively) compared to broadcast application of manure (43%) indicating that N losses were lower. However, further knowledge on soil N transformation and N loss pathways in systems with slurry injection is needed.     

Organic Matter Management as an Underlying Cause for Soil Fertility Gradients on Smallholder Farms in Zimbabwe

Management of spatial and temporal variability of soil fertility within fields and farms is one major challenge for increasing farm-level crop productivity in smallholder agriculture. A study was conducted across 120 on-farm field sites in three agro-ecological regions of Zimbabwe to identify management factors influencing the formation of within-field/farm soil fertility gradients. Using farmer participatory research approaches, host farmers were put into three classes according to resource endowment, namely, Resource-endowed, Intermediate and Resource-constrained farmers. Each host farmer identified the most (rich) and least (poor) productive field or field section, which were then studied over two years. Farmer criteria for defining soil fertility ranged from colour through elements of soil structure to crop response following external nutrient inputs. The fertility ranking of fields consistently matched with laboratory indices, with rich fields containing significantly more soil organic carbon (SOC) and nutrients than the corresponding poor fields. Fertility gradients were evident within and across farms belonging to different farmer classes. The mean SOC content for rich fields were >6.0 g kg⁻¹ compared with <4.6 g kg⁻¹ for the designated poor fields. Rich fields belonging to Resource-endowed farmers had 16–28% more SOC than those belonging to their resource-constrained counterparts, suggesting differences in organic matter management. Differences in SOC and fertility status between rich and poor fields were wider in two of the study areas which had more than 70 years of cultivation in contrast to the third site which had been under smallholder farming for only 20 years, suggesting that the observed fertility gradients are a cumulative effect of years of differential management practices by different farmer classes. Analysis of potential benefits from in situ organic biomass inputs suggested that the processes of organic matter capture and utilization discriminated against Resource-constrained farmers. About 50% of in situ biomass, preferentially maize stover, was lost in three dry season months, and up to 72% of potentially recyclable N is lost from poor fields managed by Resource-constrained farmers. In contrast, Resource-endowed farmers incorporated more than 1.5 t C, 25 kg N and 5 kg P ha⁻¹ season⁻¹ because of their access to draught power during the early dry season. Such inputs could make a difference on these nutrient-depleted soils. Intermediate farmers represented a diverse transitional group whose size and variability could be indicative of the dynamism of technology usage. It was concluded that management of soil fertility gradients to increase crop productivity on smallholder farms hinges on increasing the capacity and efficiency with which organic matter is generated and utilized by different farmer weaclth groups across temporal scales.     

Nitrogen (N) management in the ‘De Marke’ dairy farming system

In the sandy regions of The Netherlands, high losses of N from intensified dairy farms are threatening the environment. Therefore, government defined decreasing maximum levy-free N surplusses for the period 1998–2008. On most dairy farms, the current N surplus has to be reduced by half at least. Farmers fear that realizing these surplusses will be expensive, because it limits application of animal manure, which then has to be exported or additional land has to be bought. Moreover, farmers are worried about the impact on soil fertility. To explore the possibilities for reducing surplusses of average intensive farms by improved nutrient management, farming systems research is carried out at prototype farm De Marke. Results are compared with results of a commercial farm in the mid-1980s, the moment that systems research started and introduction of the milk quota system put a halt to further intensification. Results indicate that average intensive farms can realise a reduction in N surplus to a level below the defined final maximum, without the need to buy land or to export slurry. Inputs of N in purchased feeds and fertilisers decreased by 56 and 78%, respectively. Important factors are reduced feed intake per unit milk, as a result of a higher milk yield per cow, less young stock and judicious feeding, an improved utilization of home-made manure and a considered balance between the grassland and maize area. Changed soil fertility status did not constrain crop production. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg l^-1, within a few years.     

Determinants of farmers’ decision to adopt or not adopt inorganic fertilizer in the savannas of northern Nigeria

Soil nutrient deficiency has hampered increased agricultural production in the savannas of northern Nigeria. It has been observed that inorganic fertilizer (IF) has the potential to reverse the situation. However, low adoption among the farmers has characterized IF in the savannas of northern Nigeria. The application rates have also fallen far lower than the rate recommended by research and extension, resulting in low crop yields. This paper investigates the factors that influence farmers' decision to adopt or not to adopt IF and to evaluate the elasticity of adoption. This information will help to prioritize the factors that affect IF adoption decisions and suggest pathways for effective promotion of IF. About 49% of the survey farmers adopted IF and the application rate ranges from 5.6 to 64.4 kg ha^–1 (with a mean of 24.1 kg ha^–1). The probability of adoption increases with increased targeting of: farmers from the Guinea savanna agroecological zone, younger farmers, better educated farmers, food secure farmers and net sellers of food grains, farmers who have diversified into many crops, farmers who perceive increase in the fertilizer needs of their crops, and farmers who apply large quantities of organic manure. Among others, the estimates of elasticity of adoption indicate that a 1% increase in the number of farmers who perceive an increase in the fertilizer needs of their crops results in 3.23% increase in the probability of IF adoption. The paper concludes with policy implications for strategies aimed at promoting IF in the savannas of Nigeria and similar ecologies elsewhere.     

Balanced pasture fertilization in the Basque Country: I. Phosphorus and potassium budgets on dairy farms

Dairy farming is the main agricultural activity of the Basque Country. A dairy farm is characterized as a system with soils and crops, forage, cattle and manure as main components, and in such a system, nutrient cycling is very important to maintain soil fertility and optimize forage production. To quantify nutrient transfers in the cycle, a simple system was developed and has been applied to seventeen farms to examine its ability to achieve a balanced P and K fertilization. These farms have provided data on inputs (fertilizer, feeds, concentrates), pasture and manure management, and outputs (milk production), and soil samples have been taken from farm pastures. Phosphorus and K in excreta and uneaten pasture is used with a relatively high efficiency as suggested by the relatively high efficiency of P and K utilization by the pasture that usually ranges from 70 to 90%. Concentrate feeding (3000 kg cow^–1 yr^–1) represents one of the main P and K inputs in Basque Country dairy farms, averaging 26 and 66 kg ha^–1, respectively. Besides, release of K in the soil through slow liberation from non-exchangeable sites was estimated as 30 kg ha^–1. Thus, a high efficiency in excreta recycling would diminish substantially P and K mineral fertilizer needs. Farm nutrient budgets appear to be a convenient tool for determining nutrient shortages and surpluses at farm level, and thus they are considered as a first step to support a better management of maintenance fertilization of permanent pastures.