Rice is the most important staple food in Liberia, accounting for more than 60% of the national caloric intake and being a major source of income and food in rural areas of both upland and lowland agro, ecologies [1]. However, the country’s rice production hardly meets the demand, with yields stagnating at around 1.01.6 t/ha, which is far below the West African average of 2.53.0 t/ha and of the potential yield of improved varieties, which can produce 46 t/ha under proper management [2][3].

Consequently, Liberia depends on the imports of rice in excess of 300,000 metric tons annually and thereby becomes susceptible to the fluctuations of the global market and pressure on foreign exchange [4]. The main, deep, seated structural problem, which has limited the productivity of rice crops over the years, is the degradation of soil fertility due to intensive cultivation, reduced fallow periods, slash, and, burn land clearing, and little use of nutrients either from organic or inorganic sources. Moreover, these problems aggravate due to the nature of Liberia’s highly weathered tropical soils, which are acidic, deficient in nitrogen and phosphorus, and easily lose nutrients when continuously cropped [5].

Integrated Soil Fertility Management (ISFM) is a ground, breaking package of measures that have been highly efficient in correcting depleted soils and raising the overall productivity of farming systems in SSA.

The African Soil Health Consortium published a definition of ISFM that describes it as a deliberate combination of the use of organic materials, mineral fertilizers, better seeds and site, specific agronomic practices, with the main objective of increasing the efficiency of nutrient use by crops and the simultaneous development of soil fertility on a sustainable basis [6].

The main difference between ISFM and traditional approaches that rely only on fertilizer is the former’s capability to illustrate and utilize the positive interactions between organic matter, soil microbes, water holding capacity, and crop genetic potential. Agricultural experiments in West Africa reveal that under certain conditions, flooded rice crops yields can be increased by 30,150% as a result of ISFM interventions, those conditions being soil type, water regime, management intensity [7].

In Liberia, however, a very small percentage of farmers have adopted the practices due to limited extension services, very high prices of fertilizers, lack of labor, and scanty knowledge among farmers on correct ISFM application [8].

Climate variability is one of the main reasons soil fertility management has to be made more efficient. Changes in rainfall patterns, floods recurring in low, lying areas, and droughts lasting longer in highland areas have all interfered with rice production and made it difficult for farmers to rely on their usual methods [9].

ISFM helps to make farms more climate, resilient by improving the soil condition, water retention, and nutrient holding capacity, thereby ensuring stable and increased rice yields even in the face of climate change [10].

However, the data and models depicting how ISFM can be most effectively utilized in Liberia’s different agricultural zones are scarce. This research is intended to fill the void by integrating biophysical, agronomic, and socioeconomic data sets to determine the productivity effect of ISFM and put forward a national ISFM adoption plan that harmonizes with Liberian rice systems. By conducting such a thorough study, the research seeks to enable the formulation of rice production strategies which are not only scalable but also farmer, centered and sustainable.

Rice is the staple food of Liberia and the entire West African region, accounting for a major part of the household caloric intake, as well as being a critical economic and social commodity. However, domestic rice production has not been able to keep up with national demand resulting in a continuous reliance on imported rice [11]. The average rice yields in Liberia is generally 1.01.6 t/ha and still far below the potential yield range of 46 t/ha, even under rain, fed conditions and with improved varieties [12]. This discrepancy reflects a complex combination of agronomic, biophysical, socioeconomic and institutional factors, among which soil fertility decline has been recognized as the most frequent and significant one. Most of the land cultivated in Liberia comprises highly weathered tropical soils, which are normally low in native nitrogen, have low phosphorus availability due to fixation by iron and aluminum oxides, and possess delicate soil organic matter pools that can easily be depleted under continuous cropping [13]. The conventional shifting cultivation method that was once sustainable when the fallow period was 1015 years is now ecologically unsustainable due to population pressure that shortens the fallow period and farmers are forced to go back to the fields before the soil nutrients have been fully regenerated. Over time, these dynamics have created a landscape where nutrient mining, low fertilizer use, and insufficient biomass return have led to severe and widespread soil degradation.

Among other things, Integrated Soil Fertility Management (ISFM) has been identified as one of the ways that can help to restore soil health and increase crop productivity in sub, Saharan Africa (SSA). ISFM refers to a comprehensive plan that utilizes organic materials, mineral fertilizers, good quality seeds, and climate, responsive agronomic practices to achieve higher nutrient, use efficiency and restore soil functions simultaneously [14]. The main focus of ISFM is the beneficial effects of combining different soil amendments, conjuring soil microbial activities, and plant nutrient uptake. For example, organic matter can increase soil porosity, reduce evaporation, and boost microbial diversity, thus crop fertilizer utilization efficiency will improve. A number of global studies have demonstrated that ISFM has the potential not only to conserve nutrients and reduce nitrogen losses but also to achieve remarkably high yields through lowering fertilizer inputs over a wide range of agro, ecological settings [15][16]. Research covering different continents such as Asia, Latin America and Africa has demonstrated, as a whole, that proper nutrient management can result in yield being doubled or even tripled when organic residues are used together with mineral fertilizers. However, the extent of such increases depends on factors such as soil type, rainfall, and crop genetics [17].

Research carried out in West Africa has revealed results along these lines, especially with rice, based systems. Survey work done in Ghana, Nigeria, Côte d’Ivoire, and Sierra Leone has shown considerable yield enhancements when organic amendments are mixed with mineral fertilizers in both upland and lowland rice settings [18][19]. Inland valley swamp (IVS) systems which make up a significant part of Liberia’s rice production area, are particularly responsive to integrated nutrient management as a result of their great capability for water retention and sediment nutrient deposition. Work in the West African IVS areas has demonstrated that the combination of 24 t/ha of organic matter with 6090 kg NPK/ha can achieve yield increases of 40,120%, subject to varietal choice and water management [20].

Better germplasm, especially the New Rice for Africa varieties (NERICA), has also been demonstrated to have a higher nutrient, use efficiency, thus farmers can gain more yield advantages from both organic and mineral nutrient sources (AfricaRice, 2018). These new insights highlight the necessity of associating improved varieties with well, controlled soil fertility management practices so as to realize the complete yield potential of the West African rice systems.

Soil fertility and ISFM research in Liberia has not even reached the level of neighboring countries, however, new evidence shows that the soil problems may be the same. The Ministry of Agriculture and AfricaRice soil test results show that the upland soils are very low in nitrogen, phosphorus which is quite available is at non, optimal levels, and the soils have a low cation exchange capacity, these three factors contribute to limiting the effectiveness of mineral fertilizers when they are applied alone [21]. As a result of biomass removal, burning, and short fallowing periods, organic matter content is low in general, and soil acidity that is typical in the rainforest areas of Liberia is a double problem as it reduces nutrient availability and also discourages root growth [22]. Small pilot projects in Bong, Lofa, and Nimba counties that combined compost, manure, and minor quantities of mineral fertilizer have resulted in good yield increases, however, the impacts have not been scaled and to be evaluated yet. These pilots brought to light that by integrating organic matter along with moderate doses of fertilizer, rice yields could be increased by 3080%, however, such achievements are heavily reliant on continuous water management, correct time of operation, and the choice of the right variety.

Adoption challenges in Liberia largely reflect the general West African situation but they are exacerbated locally through, among other factors, the lacking market infrastructure, high transport costs and the irregular supply of fertilizer. Several studies emphasize the fact that the fertilizer distribution network is very poorly developed so that farmers either have to cover very long distances or to depend on government programs that are subsidized, inconsistent, and usually politically influenced [23]. Lack of soil testing services further prevents farmers from making a well, informed decision on nutrient management, which leads to improper use of inputs and limited crop response.

Moreover, Liberia’s national extension system is still understaffed and underfinanced, hence the limited dissemination of ISFM knowledge and decreased awareness of improved soil fertility practices among farmers. The country’s civil conflict broke traditional farming systems and lowered institutional capacity, thus agricultural knowledge transfer and research continuity still face long, term problems [24].

On the whole, the literature indicates that ISFM is scientifically proven and contextual suitable to Liberia’s soil and climate conditions, however, a successful implementation depends on understanding the constraints, opportunities, and decision, making processes of farmers at the local level. This research utilizes global and regional data, and at the same time, meets Liberia’s distinct knowledge gaps by applying an integrated analytical method that considers the interaction of soil nutrient dynamics, yield output, and adoption factors.

Figure 1.Conceptual framework.

The foundation of the conceptual framework for this research is the central tenets of Integrated Soil Fertility Management (ISFM). As indicated in Figure 1Figure 1 above, this approach underlines the synergistic blend of improved germplasm, organic materials, mineral fertilizers, and site, specific agronomic practices. These factors complement each other and their interaction can lead to a significant enhancement in nutrient, use efficiency, soil health as well as increased resistance to climatic changes.

The use of improved germplasm is the biological basis of ISFM as it results in rice varieties which have a higher yield potential, stronger root systems, and better responsiveness to nutrient inputs. Organic matter additions e.g. compost, manure, and crop residues are indispensable in the restoration of soil organic matter, the improvement of soil structure, the increase of soil cation exchange capacity, and the stimulation of microbial activity [25].

These changes help in retaining nutrients in the soil and releasing them gradually and consistently. Mineral fertilizers serve as a substitute for nutrient elements which are immediately available with a special focus on nitrogen and phosphorus which are in short supply in Liberia’s highly weathered tropical soils. This mix of inputs makes certain that there is a source of nutrients both at the moment and in the future, and also that fertilizer inefficiencies caused by leaching, runoff, and soil acidity are minimized. Together, these biophysical factors form a cohesive system that focus on the underlying problems of low rice productivity instead of simply treating the symptoms.

The framework as shown in Figure 1Figure 1 also has a socioecological aspect that acknowledges how local farming practices, knowledge systems, institutional support, and environment can significantly affect ISFM implementation. Local agronomic methods like proper spacing, timely weeding, water management in inland valley swamps, liming for acidic soils, and efficient nutrient application are necessary to get the most out of combining organic and inorganic input materials. Farmers’ decisions depend on the availability of labor, access to inputs, land tenure systems, and the quality of extension services. Therefore, the adoption and success of ISFM are not just about technical feasibility but also about social and economic limitations and motivators.

On top of that, climate change is making the situation more complicated, so practices like adding organic matter and saving soil moisture are now even more important for protecting rice systems from drought and irregular rainfall. This conceptual framework, which combines biophysical changes with social and economic conditions, offers a well, rounded foundation to assess the effectiveness of ISFM and come up with the right kind of scaling interventions for Liberia’s different rice production ecologies.

To assess whether Integrated Soil Fertility Management (ISFM) can be a tool for boosting rice productivity in the main agro, ecological zones in Liberia, the research took an integrated methodological framework. This framework synthesizes soil nutrient profiling, agronomic systems analysis, yield, response data, and socioeconomic adoption assessment, thus providing a multi, layered understanding of ISFM performance in Liberian contexts. Such a method corresponds to the ISFM frameworks for West Africa studies and the first of these is the local biophysical and institutional settings [26][27].

This paper of adoption and feasibility assessment is based on a variety of different factors such as socioeconomic, institutional, labor, and market, related that determine the capability as well as the willingness of the farmers to use ISFM practices in the different rice, growing ecologies of Liberia. Adoption capacity was studied by means of a multi, criteria framework that looks into the accessibility of the inputs, availability of household labor, gender roles in the field operations, extension service coverage, land tenure security, and the financial constraints that affect the purchases of fertilizers and organic inputs. The market diagnostics took into consideration aspects of the fertilizer supply chain, cost of transportation, input price volatility, and the trustworthiness of the distribution networks, especially in the remote counties where the massive logistical barriers significantly increase the price of ISFM adoption. The level of knowledge of the farmers as well as their perception of the decline in soil fertility were measured with the help of LSMS, ISA indicators and the qualitative information gathered from the extension agents, showing that the lack of knowledge about the best time, location, and integration of organic and mineral nutrients is still a major barrier. Labor feasibility was determined through the analysis of household labor calendars that helped to recognize the seasonal work bottlenecks for the preparation of compost, transport of manure, construction of bunds, and water regulation in the inland valleys.

Besides, the strength of Liberia’s extension system, the availability of training programs, the presence of NGO, led soil fertility initiatives, and the extent to which national agricultural policies support fertilizer subsidies or local input production were utilized to further determine the institutional feasibility. The combined social, economic, and institutional variables were then incorporated into an adoption scoring matrix which made it possible to classify the counties into high, medium, and low, feasibility zones.

The matrix also provides a contextual basis for interpreting the ISFM yield increases not only as agronomic options but as interventions that require enabling systems, supportive policies, and farmer, centered extension strategies in order to be successfully adopted at a large scale.

The findings of this research offer compelling empirical and theoretical evidence supporting the use of Integrated Soil Fertility Management (ISFM) as a strategy with a high impact on increasing rice productivity in different agro, ecological areas of Liberia. The yield responses indicate that the combination of organic matter inputs with moderate rates of mineral nitrogen leads to significantly higher productivity compared to either input alone, in line with the well, known ISFM principle that it not only provides nutrient availability for a short period but also improves soil quality in the long run [28][29]. The Mitscherlich response curves indicate that the yields tend to level off earlier when organic matter is added, suggesting that organic inputs allow mineral nitrogen to be more efficiently converted into grain. This is consistent with the results of [30] and [31] who demonstrated that nutrient synergy in tropical soils lowers nutrient losses and enhances physiological nutrient uptake. This matter is very significant for Liberia’s rice systems which frequently face nutrient depletion and hardly use external inputs.

Nutrient Use Efficiency (NUE) trends from the analysis also follow previous literature which reports diminishing marginal returns to nitrogen as application rates increase. Still, the incorporation of organic matter lessens this drop, keeping NUE at higher nitrogen levels which are a proof that organic inputs improve the synchrony of nutrient release with crop demand [32][33]. Several nutrient use studies in West Africa have also demonstrated that small additions of OM (24 t/ha) greatly enhance the nitrogen recovery efficiency in severely degraded soils [34]. The increased NUE under ISFM conditions predicted by the model means that Liberia might be able to reduce the total nitrogen needed for smallholder rice production thus saving money and reducing the risk of environmental hazards such as nitrate leaching and ammonia volatilization.

The long, term improvement of soil health is thus a major factor. This is in line with the Soil Organic Carbon (SOC) trajectory which emphasizes long, term soil health benefits. Soil Organic Carbon dropped drastically in the absence of organic matter, a situation that has been repeated in West African Ferralsols and Acrisols that were continuously cultivated without the return of residues [35]. On the other hand, the use of organic matter over a long time ensured a slowdown in the loss of SOC and at the higher input level (4 t/ha) it was even able to reverse the long, term negative trends. Also, the Africa Soil Information Service (AfSIS) and long, term experiments in Cte d’Ivoire and Nigeria sources have shown that 3 to 5 t/ha of organic matter application is necessary yearly for the gradual restoration of carbon stocks in humid tropical regions.

Besides, better SOC results to improved soil aggregation, higher water retention capacity and greater biological activity of the soil which are the main factors that make crops more resistant to rainfall variability that is a major vulnerability of Liberia’s upland and rain, fed lowland rice ecologies.

The sensitivity analysis further refines the picture by showing that rainfall variability and soil acidity remain the major factors affecting the yields, even when best ISFM treatment is used. A 20% change in rainfall resulted in 1022% variations in yield, which is in line with the literature pointing to water availability as being the key factor determining nutrient response in humid West African rice systems [36]. The decrease in yield due to acidic soils, particularly under pH 5.5, was quite significant as a result of phosphorus fixation and root damage, a problem which is widely known in Liberia and has been confirmed in Sierra Leone and Ghana through research [37].

Furthermore, high, quality organic matter helped increase yields and NUE, whereas low, quality OM reduced short, term productivity but enabled long, term SOC accumulation, a compromise that is recognized in the organic resource quality framework by [38].

In spite of the strength of the modeling framework, several limitations should be pointed out. Most of the results are based on secondary datasets and calibrated response functions rather than on extensive primary field trials carried out specifically in Liberia [39]. Thus, the modeled yield results are theoretical averages under certain assumptions and might not adequately reflect the heterogeneity of on, farm conditions, such as small variations in soil fertility, farmer management skills, pest pressures, and local climate shocks.

Besides, the farmers’ fields are likely to have patchy nutrient distribution and varying input application, which might lead to yield responses lower or more variable than simulated estimates. In addition, the Mitscherlich model presupposes smooth and continuous yield responses that may not correspond to threshold effects or nonlinear constraints that exist under severe nutrient stress [40].

These limitations, however, do not invalidate the conclusions. They rather serve as a warning that the yield gains projected by the models should be viewed as a potential indication instead of a promise, which is why on, farm validation trials and adaptive extension approaches are vital to improving ISFM recommendations in real, world situations.

1) Prioritize water & acidity first: finance bunding/mulch in uplands and banded P + micro-liming where pH < 5.5; these stabilize responses to N and OM.

2) Subsidize smart, not flat: replace blanket fertilizer subsidies with targeted P vouchers tied to band placement and acidity mapping; keep a modest N co-pay to maintain efficiency.

3) Lower the labor hump: promote on-farm compost pits, near-field OM, and simple placement tools; support cash-for-work for communal water works pre-season.

4) Package ISFM as kits: seed + (modest) N + banded P + one training; escalate OM rate over 2 - 3 seasons as SOC and logistics improve.

5) Extension metrics: track NUE, pH screening coverage, bund length constructed, and OM rate achieved (not just fertilizer tons).

6) County targeting: roll out “Acid-Soil Booster” where pH < 5.5; deploy “Labor-Light ISFM” in labor-scarce uplands; use “Starter Kits” for low-adoption districts.