Quantifying the prevalence of (non)-response to fertilizers in sub-Saharan Africa using on-farm trial data

Poor and variable crop responses to fertilizer applications constitute a production risk and may pose a barrier to fertilizer adoption in sub-Saharan Africa (SSA). Attempts to measure response variability and quantify the prevalence of non-response empirically are complicated by the fact that data from on-farm fertilizer trials generally include diverse nutrients and do not include on-site replications. The first aspect limits the extent to which different studies can be combined and compared, while the second does not allow to distinguish actual field-level response variability from experimental error and other residual variations. In this study, we assembled datasets from 41 on-farm fertilizer response trials on cereals and legumes across 11 countries, representing different nutrient applications, to assess response variability and quantify the frequency of occurrence of non-response to fertilizers. Using two approaches to account for residual variation, we estimated non-response, defined here as a zero agronomic response to fertilizer in a given year, to be relatively rare, affecting 0–1 and 7–16% of fields on average for cereals and legumes respectively. The magnitude of response could not be explained by climatic and selected topsoil variables, suggesting that much of the observed variation may relate to unpredictable seasonal and/or local conditions. This implies that, despite demonstrable spatial bias in our sample of trials, the estimated proportion of non-response may be representative for other agro-ecologies across SSA. Under the latter assumption, we estimated that roughly 260,000 ha of cereals and 3,240,000 ha of legumes could be expected to be non-responsive in any particular year.

Low Soil Nutrient Tolerance and Mineral Fertilizer Response in White Guinea Yam (Dioscorea rotundata) Genotypes

Yam (Dioscorea spp.) is a major food security crop for millions of resource-poor farmers, particularly in West Africa. Soil mineral deficiency is the main challenge in yam production, especially with the dwindling of fallow lands for the indigenous nutrient supply. Cultivars tolerant to available low soil nutrients and responsive to added nutrient supply are viable components of an integrated soil fertility management strategy for sustainable and productive yam farming systems in West Africa. This study’s objective was to identify white Guinea yam (D. rotundata) genotypes adapted to available low soil nutrients and responsive to externally added nutrient supply. Twenty advanced breeding lines and a local variety (Amula) were evaluated under contrasting soil fertility, low to expose the crop to available low soil nutrient supply and high to assess the crop response to added mineral fertilizer (NPK) input at Ibadan, Nigeria. The genotypes expressed differential yield response to low soil fertility (LF) stress and added fertilizer input. Soil fertility susceptibility index (SFSI) ranged from 0.64 to 1.34 for tuber yield and 0.60 to 1.30 for shoot dry weight. The genotypes R034, R041, R050, R052, R060, R100, and R125 combined lower SFSI with a low rate of reduction in tuber yield were identified as tolerant to LF stress related to the soil mineral deficiency. Likewise, the genotypes R109, R119, and R131 showed high susceptibility to soil fertility level and/or fertilizer response. Genotypes R025 and R034 had the tuber yielding potential twice of that the local variety under low soil nutrient conditions. Shoot dry weight and tuber yield showed a positive correlation both under low and high soil fertility conditions (r = 0.69 and 0.75, respectively), indicating the vigor biomass may be a morphological marker for selecting genotypes of white Guinea yam for higher tuber yield. Our results highlight genotypic variation in the tolerance to low soil nutrients and mineral fertilizer response in white Guinea yam to exploit through breeding and genetic studies to develop improved genotypes for low and high input production systems in West Africa.

Customized Fertilizers- An Artefact in Indian Agriculture: A Review

Indian agriculture is suffering from low crop productivity and poor sustainability as its land suffers from varying degrees of soil fertility depletion. There exists a wide gap between amount of nutrients removed by crops and added through fertilizers resulting in reduced yields is due to mineral deficiency. Besides, there are issues of poor fertilizer response and reduced fertilizer use efficiency. Therefore, the holistic approach should be soil-climate-crop specific. It is essential to supply both macro and micronutrients to cater the needs of the crop. As Indian soils are deficit in supplying nutrients especially nitrogen and zinc, customized fertilizer is one option, being a multi-nutrient carrier of both macro and micro nutrients, is tailored to meet the region, soil, crop specific needs designed through specialised smart fertilizer technology, manufactured through systematic granulation process. These, customized fertilizer boost crop yields and arrest soil fertility deterioration over long run in a sustainable manner.

Nutrient Dynamics in Switchgrass as a Function of Time

There are wide variations in fertilizer recommendations for switchgrass (Panicum virgatum L.) as biofuel feedstock or forage. Inconsistent yield responses to fertilization are common. Nutrient translocation, from aboveground leaves and stems to belowground roots, is a contributor to variable, and sometimes the absence of, fertilizer response. A field study evaluated how major nutrients are cycled within switchgrass during the growing season. Aboveground (AG) and belowground (BG) biomasses were harvested and analyzed separately for yield (AG) and nutrient concentrations (AG and BG). Maximum yields were 26.3 (2008), 17.5 (2009) and 29.3 (2010) Mg ha−1 until senescence. In all years, the N concentration of the AG biomass decreased as the season progressed (p < 0.0001). The belowground biomass N concentration increased over time in 2008 and 2010 (p < 0.05). Phosphorus (P) and potassium (K) displayed similar trends to nitrogen concentration. Temporal changes of other nutrients in the AG and BG biomass concentrations were inconsistent and varied compared with N. The dynamics of the macronutrients suggested translocation from AG to BG as the switchgrass matured. Nutrients stored in roots can be beneficial for regrowth in the following growing season, which may reduce response to fertilizers. A greater understanding of nutrient cycling and harvest timing is needed to better manage different switchgrass production systems.

Developing a Sustainable Management Strategy for Quantitative Estimation of Optimum Nitrogen Fertilizer Recommendation Rates for Maize in Northeast China

Excessive application of chemical fertilizers has caused a series of environmental problems, including environmental pollution. Quantitative estimation of a sustainable fertilizer recommendation rate is paramount for formulating fertilizer management strategies to improve productivity of low-yield regions and to prevent environmental damage. In this study, the database was drawn from 31 experimental sites in the main maize production region of Northeast China, during the period 2009 to 2013, to study the relationships between yield factors and nitrogen application rates, and to explore sustainable nitrogen (N) fertilizer recommendation rates based on analysis using the fertilizer response model. The fertilizer response model method is a technique that can provide effective performance predictions for the estimation of the optimum crop balanced fertilizer rates in varied agricultural regions. Results revealed that the average grain yield in treatment of N180 (the amount of nitrogen application rate was 90 kg ha −1) was highest, and the yield increase rate ranged from 4.77% to 58.53%, with an average of 25.89%. The sequence of grain yields in each treatment receiving N fertilizer management from high to low was: N180 > N270 > N90 in all the regions. The agronomic efficiency for applied N in N90, N180, N270 treatments was 11.8, 10.8, and 4.6 kg kg −1, respectively. The average optimum N fertilizer recommendation rate in Liaoning province was 180.4 kg ha −1, and the predicted optimum yield ranged between 7908.7 and 12,153.9 kg ha −1, with an average of 9699.1 kg ha −1. The mean optimum N fertilizer recommendation rate in western (WL), central and southern (SCL), eastern (EL), and northern (NL) of Liaoning province were 184.2, 177.2, 163.5, and 192.5 kg ha −1, and the average predicted optimum yields were 8785.3, 10,630.3, 9347, and 9942.4 kg ha −1. This study analyzed the spatial distribution of optimum fertilizer recommendation rates and the corresponding theoretical yield based on a large database, which helped to develop effective and environment-friendly N management strategies for sustainable production systems.

The Estimation of Nitrogen Uptake and Utilization Efficiency in Cotton by the Fertilizer-Response Model

Due to the indeterminate growth habit of cotton crops, a better understanding of N status at the rational fertilizer regime is important to promote lint yield. The fertilizer-response model was employed to evaluate N status by analyzing data of shoot dry mass, N content and N concentration at different growing stages. A field study was conducted on drip-irrigated cotton plants with N fertilizer addition in total amounts of 0 (N0), 120 (N1), 240 (N2), 360 (N3) and 480 (N4) kg ha-1 in Xinjiang, China in 2016. Thirty percent of total fertilizers were applied at planting and the rest 70% were applied over six applications. The N fertilizer treatment at the accumulative rate of 70 kg ha-1 was enough to induce the N status of steady state accumulation 60 days after germination. Since 90 days the treatments that delivered the N amount between 120 and 240 kg ha-1 was deficient for cotton demand, higher rates from 360 and 480 kg ha-1 induced inherent N reserve and resulted in the highest level of yield. With regard to the practical meaning, the N fertilizer dose of 360 kg ha-1 can be used for cotton growth. The N fertilizer dose of 120 kg ha-1 can be recommended when the yield of 5,840 kg ha-1 lint can meet the goal of cotton culture. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

Determination of Fertilizer Doses of Sweet potato (Ipomoea batatas L.) “Rancing”

Nitrogen, phosphorus, and potasium availability are the most thresholding factors for maximum growth and yield. The tuber yield of sweet potato varies depending on growing area therefore a fertilization program, especially in the type and the dose of the fertilizers, is required. This research was conducted in the Pasir Muncang experimental farm at Gadog, Bogor, West Java, Indonesia. The study site is located ±500 meters above sea levels, 6°39’31.90” south latitude and 106°52’7.77” east longitude. The experiment was started in May to September 2017. Multi nutrient response method was used for this study, and the interpretation of the results was used to develop fertilizer recommendations using single-nutrient quadratic model. The recommendation was determined using N, P2O5, K2O fertilizer response curve, where the first recommendation was calculated from the maximum relative yield,and the second, third, and fourth recommendation were determined from N, P2O5, K2O threshold. Each treatment for N, P and K was evaluated with different level of fertilizer dose using a randomized complete block design with three replications. The fertilizer doses were 50, 100, 150 and 200% from reference (100% N = 100 kg N ha-1, 100% P = 75 kg P2O5 ha-1, dan 100% K = 100 kg K2O ha-1). Relative yield of sweet potato (y), response to fertilizer (x) had improvement quadratically with equation y = -0.0017x2 + 0.538x + 40.035 for N, y = -0.0041x2 + 0.8595x + 38.211 for P2O5, and y = -0.0025x2 + 0.4318x + 73.377 for K2O. The optimized dose of fertilizer to get maximum yield of sweet potato tuber is 158.23 kg ha-1 of N, 78.60 kg ha-1 of P2O5, and 83.60 kg ha-1 K2O, or 343.97 kg ha-1 of Urea, 218.53 kg ha-1 of SP36 139.33 kg ha-1 of KCl.Keywords: multi nutrient response, nitrogen, relative yield, phosphorus, potassium