Omission Trials Research Articles

Boron availability and fertilizer response of maize in soils from sub‐Saharan Africa

AbstractBackground and aimsLow boron (B) availability is associated with strongly weathered, coarse‐textured, and low organic matter soils, widespread in sub‐Saharan Africa (SSA). It is unknown to what extent B fertilization can increase maize yields in SSA. This study aims to understand the soil properties controlling B availability to field‐grown maize.MethodsBoron fertilizer omission trials with maize were executed at 15 sites in Kenya, Zambia, and Zimbabwe. Yield, B uptake, and soil parameters potentially relevant for B availability, including extractable soil B (hot water, 0.01 M CaCl2, and 0.43 M HNO3), were determined.ResultsSoil B pools were strongly intercorrelated and were positively correlated with organic carbon, suggesting the relevance of organic matter for soil B availability. Soil parameters described limited variation in B uptake and the yield response to B fertilization. Boron fertilization did not increase yields in any of the 15 sites but increased uptake in 11 sites. Yields were reduced through B fertilization in five sites, likely because B application induced toxicity. No clear critical soil or plant B concentrations indicating deficiency could be derived, but positive yield responses to B fertilization were absent with hot water B levels above 0.69 mg kg−1.ConclusionAssessing B fertilizer needs in maize grown in tropical soils based on soil or plant tissue concentrations remains challenging. Improving soil organic matter status could potentially alleviate B deficiency in crops when present. Recommendations are given to overcome the identified challenges associated with studying B availability in tropical soils.

Omitting the Application of Nitrogen or Potassium Reduced the Growth of Young Chestnut (Castanea sativa) Trees, While a Lack of Boron Decreased Fruit Yield

The chestnut tree (Castanea sativa Mill.) is gaining importance in the mountainous regions of southern Europe due to the high value of its fruits. It is essential to establish effective cultivation protocols, considering that this species is still relatively understudied. In this study, we present the outcomes of the initial establishment of a chestnut orchard conducted through a nutrient omission trial for four years. The treatments included a fertilization plan with nitrogen, phosphorus, potassium, and boron (NPKB), the control, and four other treatments corresponding to the omission of each nutrient (-NPKB, N-PKB, NP-KB, NPK-B). The -NPKB and NP-KB treatments showed significantly lower trunk circumferences and canopy volumes compared to the other treatments. The NPK-B treatment resulted in the lowest fruit production, with a total accumulated yield (2020–2022) of 0.56 kg tree–1, a value significantly lower than that of NPKB (1.12 kg tree–1) and N-PKB (1.19 kg tree–1). The assessment of nutrient concentrations in the leaves revealed plants with deficient levels of B and K in treatments that did not receive these nutrients. Conversely, N levels in the leaves in the -NPKB treatment fell within the sufficiency range (20 to 28 g kg–1). This suggests that the sufficiency range should be adjusted to higher values, given the treatment’s effect on tree growth. It was also observed that the -NPKB treatment led to lower soil organic matter compared to the other treatments, likely due to reduced herbaceous vegetation development under the canopy, leading to decreased organic substrate deposition in the soil. The main findings of this study are that N and K were crucial elements for the optimal growth of chestnut trees, while B played a significant role in fruit production.

Assessment of Endogenous Soil Fertility to Update Fertilization of Maize (Zea mays L) Crops in the Savannah Region of Togo

The diagnosis of soil fertility is a prerequisite for the formulation of balanced and site-specific fertilizer recommendations. Macro elements (nitrogen – N, phosphorous – P and potassium – K) based nutrient omission trials were conducted in the districts of Oti, Tandjoare, Tone and Kpendjal of the Savannah region. The objective was to assess endogenous soil fertility under maize cropping to further develop updated site-specifique fertilization schemes for the crop. A total of twenty-five producers were selected in the region (eight in Tandjoare, seven in Tone, five in Oti and five in Kpendjal) for the study in a paticipatory approach. The approach was participatory in order to involve the end user in the exercise. A randomized complete block design was adopted with five fertilization treatments including N0P0K0 (T1), N0P60K70 (T2), N120P0K70 (T3), N120P60K0 (T4) and N120P60K70 (T5) kg ha-1 for the trial. The unit plot size was 100 m2 (10 m x10 m). Grain yield, yield response to nutrients and Agronomic Efficiency (AE) were determined. Genstat Edition 12th was used to discriminate means.The average yields were 0.56, 0.83, 3.18, 3.44 and 4.57 Mg ha-1 respectively for T1, T2, T3, T4 and T5 in Tandjoare, 0.32, 0.52, 1.06, 2.39 and 3.02 Mg ha-1 respectively for T1, T2, T3, T4 and T5 in Tône, 1.01, 1.35, 2.56, 3.16 and 4.39 Mg ha-1 respectively for T1, T2, T3, T4 and T5 in Oti and 0.39, 0.75, 1.54, 2.33 and 3.31 Mg ha-1 respectively for T1, T2, T3, T4 and T5 in Kpendjal. The ranking of yield data by fertilizer treatment indicates that all three macronutrients (N, P and K) are required for maize production in the Savannah region, with a priority ranking of N>P>K. The results also showed that the best Agronomic Efficiency is obtained when all macronutrients are supplied in all four districts. The results of this diagnostic will be used as a basis for formulating balanced, site-specific fertilizer recommendations for intelligent, environmentally-friendly agriculture.

Investigation of Yield Limiting Nutrients for Wheat Productivity through Nutrient Omission Trials

This study examines the effect of nutrient omission trials (NOTs) on wheat productivity in West shawa zone, Oromia region, with a focus on identifying yield-limiting nutrients. The experiments were conducted out over ten experimental sites. The experiment was laid out by randomized block design using farmers plot as replications per villages to determine the primary yield-limiting nutrients in wheat crop production using nutrient omission strategies and different nutrient sources. Different source of nutrients were used for the studies. Soil samples were tested to determine the initial nutrient levels, and agronomic data on growth, yield, and efficiency measures were obtained. The results show significant differences in wheat growth and production among treatments, indicating the significance of nitrogen and phosphorus in biomass and grain yield increase. The full NPKSZnB treatment consistently produced the highest yields, demonstrating the necessity of balanced nutrient management strategies specific to local agro-ecological conditions.

Appraisal of the Diagnosis and Recommendation Integrated System and Nutrient Status of Pineapple (Ananas Comosus L.) Growing Fields

ABSTRACT The diagnosis and recommendation integrated system (DRIS) has such high reliability that it can be used to evaluate many crops. Therefore, in order to have a practical database for these norms, this study was conducted to evaluate the established DRIS norms for plant pineapples (Ananas comosus L.) and to assess their nutrition status in an acid sulfate soil. Healthy and disease-free leaf samples of 8-month-old pineapple plants without fruits were collected from experimental fields with nutritional omission trials and from farmers’ fields at four cultivating sites. Nutrient concentrations were analyzed to determine DRIS indices. The result showed that the + 7 leaf was highly reliable to diagnose the macro-nutrition status, while the + 1 leaf and + 3 leaf lacked the nutrient ratios pair to assess P and Mg nutrition status. Based on the average DRIS indices of the four sites, the nutrient surplus was observed in the order P>Mn>Fe>Ca (81.7 > 52.8 > 15.7 > 13.3), while nutrient deficiency varied in the order K>Zn>N>Mg (−88.2<-20.3<-16.4<-10.7) at the + 7 leaf. The DRIS norms needed to be calibrated to obtain nutrient ratio pairs for P in the + 1 leaf, and P and Mg at the + 3 leaf.

Crossmodal visual predictions elicit spatially specific early visual cortex activity but later than real visual stimuli.

Previous studies have indicated that crossmodal visual predictions are instrumental in controlling early visual cortex activity. The exact time course and spatial precision of such crossmodal top-down influences on the visual cortex have been unknown. In the present study, participants were exposed to audiovisual combinations comprising one of two sounds and a Gabor patch either in the top left or in the bottom right visual field. Event-related potentials (ERPs) were recorded to these frequent crossmodal combinations (standards) as well as to trials in which the visual stimulus was omitted (omissions) or the visual and auditory stimuli were recombined (deviants). Standards and deviants elicited an ERP between 50 and 100 ms of opposite polarity known as the C1 effect commonly associated with retinotopic processing in early visual cortex. By contrast, a C1 effect was not observed in omission trials. Spatially specific omission and mismatch effects (deviants minus standards) started only later with a latency of 230 ms and 170 ms, respectively. These results suggest that crossmodal visual predictions control visual cortex activity in a spatially specific manner. However, visual predictions do not modulate visual cortex activity with the same timing as visual stimulation activates these areas but rather seem to involve distinct neural mechanisms. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

Soil zinc fertilisation does not increase maize yields in 17 out of 19 sites in Sub-Saharan Africa but improves nutritional maize quality in most sites

AimsFertilisating crops with zinc (Zn) is considered important to enhance agricultural productivity and combat human Zn deficiencies in sub-Saharan Africa. However, it is unclear on which soils Zn fertilisation can lead to higher yields and increased grain Zn concentrations. This study aimed to find soil properties that predict where soil Zn is limiting maize yields and grain Zn concentrations, and where these respond positively to Zn fertilisation.MethodsZinc omission trials were set up at multiple farm locations in Kenya (n = 5), Zambia (n = 4) and Zimbabwe (n = 10). Grain yields and tissue Zn concentrations were analysed from plots with a full fertiliser treatment as compared to plots where Zn was omitted.ResultsA positive maize yield response to soil Zn fertilisation was found at only two out of nineteen locations, despite soil Zn levels being below suggested critical concentrations at most locations. Soil properties nor plant concentrations were able to explain maize yield response to Zn fertilisation. However, positive responses in Zn uptake and grain Zn concentrations to Zn fertilisation were found at the majority of sites, especially in soils with low pH and organic carbon contents. Labile soil Zn measurements related more with Zn uptake (R2 = 0.35) and grain Zn concentrations (R2 = 0.26) than actual available Zn measurements.ConclusionsWe conclude that soil Zn fertilisation did not increase maize yields, but can increase maize grain Zn concentrations, especially in soils with low pH and organic carbon content. Predicting a yield response to Zn fertilisation based on soil properties remains a challenge.

High-throughput soil health assessment to predict corn agronomic performance

Developing high-throughput methods to quantify soil health can support decision making to minimize soil constraints for crop growth and increase sustainability in agroecosystems. This study evaluated the ability of soil health assessment conducted at the beginning of the crop growing season to predict corn agronomic performance in nutrient fertilization trials. We compared different methods to assess soil health, from the most traditional approach of measuring individual soil biochemical indicators to more novel approaches using diffuse reflectance infrared Fourier transform spectroscopy (mid-DRIFTS). Soil health was quantified using: I) traditional and emerging biochemical soil health indicators (up to 20 soil indicators), II) mineral and organic functional groups abundances estimated as peak areas in mid-DRIFTS, and III) mid-DRIFTS with partitioned spectra and partial least squares regression. Corn response to fertilizer was evaluated in a) phosphorus, potassium, and sulfur omission trials (2016–2018; 41 sites across 17 Ohio counties) as well as in b) N rates trials (2016–2017; 25 fields across 14 Ohio counties). Modeling using either biochemical soil health indicators or mid-DRIFTS accurately predicted corn yield across nutrient treatments in omission trials (R2V=0.61–0.84 in validation sets) and unfertilized controls in N rates trials (R2V=0.68–0.81) as well as corn N-driven yield gap (i.e., delta yield defined as grain yield at agronomic optimum N rate minus grain yield of the control, R2V=0.64–0.76) in N rates trials. Mid-DRIFTS approaches equaled or outperformed the predictive ability of measured biochemical soil health indicators in estimating crop performance (up to 38 % improvement in R2V), unveiling a promising method to more efficiently assess soil health. Early season soil health assessment via mid-DRIFTS has potential to directly estimate corn agronomic performance.

Effect of traditional and intensive management on soft red winter wheat yield and profitability

AbstractSome farmers regard wheat (Triticum aestivum L.) as a low‐input crop, whereas other farmers intensively manage wheat with many inputs, such as multiple foliar fungicide applications, S fertilizer, and split applications of N. This research aimed to identify the management practices that improve the yield and profitability of wheat grain and straw. An incomplete factorial omission trial was established at two locations in Ohio [the Western Agricultural Research Station (WARS) and Northwest Agricultural Research Station (NWARS)] during the 2020 and 2021 growing seasons. The tested management practices included a high seeding rate, a high N rate, a split application of N, a spring S application, a fungicide application at Feekes 9, and a fungicide application at Feekes 10.5.1. The treatments were intensive management (IM) (all tested management practices), traditional management (TM) (none of the tested management practices), and treatments consisting of the individual addition of each practice to TM or removal from the IM system. The IM increased grain yield at three of the four site‐years by an average of 0.83 Mg ha−1 but did not increase the partial economic return at any site‐year during this study. Individual treatment effects were rare and inconsistent. These results suggest that although IM can improve grain yield, it failed to do so economically at the grain prices and input costs used in this study. Farmers should use crop scouting techniques and disease forecasting tools to identify wheat fields that are likely to benefit from additional inputs such as fertilizer or foliar fungicide.

The eyes speak when the mouth cannot: Using eye movements to interpret omissions in primary progressive aphasia

Though it may seem simple, object naming is a complex multistage process that can be impaired by lesions at various sites of the language network. Individuals with neurodegenerative disorders of language, known as primary progressive aphasias (PPA), have difficulty with naming objects, and instead frequently say “I don't know” or fail to give a vocal response at all, known as an omission. Whereas other types of naming errors (paraphasias) give clues as to which aspects of the language network have been compromised, the mechanisms underlying omissions remain largely unknown. In this study, we used a novel eye tracking approach to probe the cognitive mechanisms of omissions in the logopenic and semantic variants of PPA (PPA-L and PPA-S). For each participant, we identified pictures of common objects (e.g., animals, tools) that they could name aloud correctly, as well as pictures that elicited an omission. In a separate word-to-picture matching task, those pictures appeared as targets embedded among an array with 15 foils. Participants were given a verbal cue and tasked with pointing to the target, while eye movements were monitored. On trials with correctly-named targets, controls and both PPA groups ceased visual search soon after foveating the target. On omission trials, however, the PPA-S group failed to stop searching, and went on to view many foils “post-target”. As further indication of impaired word knowledge, gaze of the PPA-S group was subject to excessive “taxonomic capture”, such that they spent less time viewing the target and more time viewing related foils on omission trials. In contrast, viewing behavior of the PPA-L group was similar to controls on both correctly-named and omission trials. These results indicate that the mechanisms of omission in PPA differ by variant. In PPA-S, anterior temporal lobe degeneration causes taxonomic blurring, such that words from the same category can no longer be reliably distinguished. In PPA-L, word knowledge remains relatively intact, and omissions instead appear to be caused by downstream factors (e.g., lexical access, phonological encoding). These findings demonstrate that when words fail, eye movements can be particularly informative.

Olive Yield and Physicochemical Properties of Olives and Oil in Response to Nutrient Application under Rainfed Conditions.

The effects of mineral fertilizers on the physicochemical properties of olives and oil under rainfed conditions is scarce. In this three-year study, the results of a nitrogen (N), phosphorus (P), potassium (K) and boron (B) fertilization trial carried out in a young rainfed olive grove and arranged as a nutrient omission trial are reported. The control consisted of the application of N, P, K and B (NPKB) and four other treatments corresponded to the removal of one of them (N0, P0, K0 and B0). Olive yield and several variables associated with the physicochemical properties of olives and oil were evaluated. The NPKB treatment increased olive yield compared to the treatment that did not receive N (N0). Although dependent on the climate conditions of the crop season, the NPKB treatment increased fruit weight and the pulp/pit ratio and its fruits tended to accumulate more oil than K0. However, the phenolics concentrations on fruits and oil tended to be lower. All olive oil samples were classified in the "extra virgin" category and all showed a decrease in its stability between 3 and 15 months of storage, regardless of treatment, especially in N0, P0 and B0 treatments. The results of the sensorial analysis indicate that all the oils fell into the medium fruitiness and greenly-fruity category. Only in P0 and B0 were defects detected, namely muddy sediment. Thus, this study seems to indicate the importance of N application, but also a balanced nutrient application and that further studies are needed, given the difficulty in finding clear trends in the response of measured variables to fertilizer treatments.

Variability in Yield Response Strongly Affects Maize Productivity and Nutrient Requirements

Smallholder maize productions systems in western Kenya exhibited wide spatial and temporal variability in yield responses to N, P and K application at the field level. Nutrient omission trials provide evidence of strong and ubiquitous N limitations and high vulnerability for rapid decline in P and K under continuous cropping without balanced nutrient applications.

Effect of Different Organic and Inorganic Inputs on Growth and Yield of Soybean (Glycine max) in Southeastern Nigeria

This study was carried out at the teaching and Research farm, Department of Horticulture and Landscape Technology, Akanu Ibiam Federal Polytechnic, Unwana, to investigate the integrated effects of organics (lime, Inoculum) and mineral fertilizers, (single superphosphate and muriate of potash) on the growth, nodulation and yield of soybean. The input omission trial was composed of 16 treatment combinations of phosphorus (75 kg/ha), potassium (88 kg/ha), lime (1500 kg/ha), and inoculum (400g/100kg seed). Each set of 16 treatments were randomized and replicated 3 times. The soybean variety “TGX1951-3F” was planted in 0.5 m by 1 m plots with a seed spacing of 5 cm. Data on number of nodules and nodule viability at 45 days after planting, plant height at 90 days after planting, number and weight of 100 seeds per plot and yield per plot at harvest were collected and analyzed using Analysis of Variance (ANOVA) in R using the package “car” to test the main treatment effects, 2-way, 3-way, and 4-way treatment interactions in the omission trial. Results showed highly significant effects of treatments on the growth, nodulation and yield of soybean. The no input treatment generally had the most appreciable improvement in plant height, nodule viability, weight of 100 seeds and yield. Inoculated seeds had the highest number of nodules and percent nodule viability (5 and 69% respectively). . 2.12ton/ha yield generated by the no input treatment shows the potential for future higher yield especially when climatic and good agronomic strategies are employed.

Compositional nutrient diagnosis and associated yield predictions in maize: A case study in the northern Guinea savanna of Nigeria

AbstractDeveloping optimal strategies for nutrient management of soils and crops at a larger scale requires an understanding of nutrient limitations and imbalances. The availability of extensive data (n = 1,781) from 2‐yr nutrient omission trials in the most suitable agroecological zone for maize (Zea mays L.) in Nigeria (i.e., the northern Guinea savanna) provides an opportunity to assess nutrient limitations and imbalances using the concept of multi‐ratio compositional nutrient diagnosis (CND). We also compared and contrasted the use of linear regression models and bootstrap forest machine learning to predict maize yield based on nutrient concentration in ear leaves. The results showed that 35% of the experimental plots had low yields due to nutrient imbalances (hereafter referred to as low yield imbalanced [LYI]). These experimental plots were dominated by control plots (without any nutrients applied), plots without N fertilization, and plots without P fertilization. Using the control plot as the ultimate indicator of nutrient imbalance, the significantly limiting nutrients in order of decreasing frequency of deficiency were N, P, S, Ca &gt; Cu, and B. Both linear regression and bootstrap forest machine learning models fairly predicted maize grain yield based on nutrient concentration in ear leaves only in the LYI group and when examining all data with an independent validation dataset. These results suggest that nutrient management strategies, especially through the site‐specific management approach, should consider S, Ca, Cu, and B in addition to the existing nutrients N, P, and K to improve nutrient balance and maize yield in the study area.

Norms Establishment of the Diagnosis and Recommendation Integrated System at Preflowering in Pineapple (Ananas comosus L.) and Its Verification in Case of Nutrient Omission Trial by Two Consecutive Crops

ABSTRACT This study was conducted to (i) establish the diagnosis and recommendation integrated system (DRIS) for the macronutrient and micronutrient status of pineapple at the preflowering stage and (ii) verify the reliability of the established norms for macronutrients. We collected 86 pineapple leaves at sites +1 and +3 from 86 fields of pineapples grown in acid sulfate soil (ASS) and analyzed their nutrient content. Findings revealed the establishment of 12 and 20 nutrient ratios for DRIS norms at pineapple leaf sites +1 and +3. Based on omission fertilization of N, P, K, Ca, and Mg at the first crop, the DRIS index of N, P, K, and Mg was inadequate in treatments lacking the corresponding nutrients, whereas the DRIS index in the treatment fully fertilized with N, P, K, Ca, and Mg was negative and lower at the +3 leaf position. In the second crop, the DRIS norms were highly reliable via the negative DRIS index when fertilizing without N, P, K, Ca, and Mg. By contrast, when fertilizing with N, P, K, Ca, and Mg, the DRIS index was positive or less negative. The DRIS norms established that position +3 is robust and suitable for evaluating the pineapple macronutrient status.

Effects of Soil Texture and Nutrients Application On Soybean Nutrient Uptake, Growth and Yield Response

Soybean is a good source of protein and calories and therefore important for food security. Soybean yields in small scale farmers field stand at less than 1.0 t ha-1 against a potential of 3 to 3.6 t ha-1. This has been attributed to low soil fertility. Although a lot of work has been carried out on Soybean nitrogen (N) and phosphorus (P) nutrition, but research findings indicate that yields are still low, raising suspicion that other nutrients could also be limiting. To investigate this, a nutrient omission trial was used in the greenhouse to find out the nutrients that limit soybean production in four distinct soil textures - clay loam, sandy clay loam, sandy clay and sandy loam following the recommended rate of 20:40:20:5:20 Kg/ha for N,P,K,Zn, and S respectively. Similarly we applied 1 ton/ha of poultry manure with thirty six treatments combinations arranged in a completely randomized design. The results revealed that soybean performance and nutrient uptake varied significantly (p&lt;0.05) between the soil texture andnutrients application. Sandy clay loam and sandy loam textures respond significantly to nitrogen, phosphorus, potassium and manure application whereas zinc and NPK nutrients limits soybean performance and uptake in sandy clay and clay loam soils. In conclusion, to increase soybean production in sandy loam and clay loam of Sudan savanna of Nigeria, fertilizer formulations containing N, P, K and Zn should be used. Manure may be used to improve soybean production in sandy clay and sandy clay loam together with application of NPK fertilizer.

Cannabidiol (CBD) drives sex-dependent impairments in omission, but has no effect on reinforcer devaluation

Habits are inflexible behaviors that persist despite changes in outcome value. While habits allow for efficient responding, neuropsychiatric diseases such as drug addiction and obsessive-compulsive disorder are characterized by overreliance on habits. Recently, the commercially popular drug cannabidiol (CBD) has emerged as a potential treatment for addictive behaviors, though it is not entirely clear how it exerts this therapeutic effect. As brain endocannabinoids play a key role in habit formation, we sought to determine how CBD modifies goal-directed behaviors and habit formation. To explore this, mice were administered CBD (20 mg/kg i.p.) or vehicle as a control and trained on random interval (RI30/60) or random ratio (RR10/20) schedules designed to elicit habitual or goal-directed lever pressing, respectively. Mice were tested for habitual responding using probe trials following reinforcer-specific devaluation as well as omission trials, where mice had to withhold responding to earn rewards. We found that while CBD had little effect on operant behaviors or reward devaluation, CBD inhibited goal-directed behavior in a sex-specific and context dependent manner during the omission task. Beyond drug treatment, we found an effect of sex throughout training, reward devaluation, and omission. This work provides evidence that CBD has no effect on habit formation in a reward devaluation paradigm. However, the omission results suggest that CBD may slow learning of novel action outcome contingencies or decrease goal-directed behavior. This work calls for further examination of sex-dependent outcomes of CBD treatment and highlights the importance of investigating sex effects in habit-related experiments.

Maize nutrient yield response and requirement in the maize belt of Nigeria

Absence of site-specific nutrient recommendation and high spatial variability of soil fertility are major factors affecting maize response to applied nutrients in Nigeria. In this study, we assessed maize response to applied nutrients and nutrient use efficiency in different management zones (MZs), for designing site-specific nutrient management recommendations for maize in the maize belt of Nigeria. The maize belt in Nigeria was earlier delineated into four MZsMZs (MZ1 to MZ4) based on soil properties. In the current study, data from two different trials, nutrient omission trials (N = 293) and fertilizer response trial (N = 705), conducted in the years 2015–2017, were extracted for MZ1 to MZ3; to analyze maize yield responses to application of N, P and K, and secondary and micro-nutrients. Maize yield response to K application was only positive in MZ1. Responses to N and P application were positive for all MZs. However, the magnitude of maize response to P varied between the MZs, indicating a differentiation in the degree to which P is limiting maize production in the study area. Average nitrogen requirement was higher for MZ3 (138 kg ha−1), than for MZ2 and MZ1 (121 and 83 kg ha−1, respectively). Average P requirement was higher for MZ3 (45 kg ha−1) than for the other zones. Potassium requirement was 26% and 28% higher in MZ2 and MZ3 compared with MZ1 (∼15 kg ha−1). The use of the specific nutrient rates for the MZs may reduce risks and uncertainties in crop production. The delineated MZs of the maize belt of Nigeria that incorporates spatial variability in soil fertility conditions are useful for nutrient management for larger areas.

Ameliorating incongruent effects of balanced fertilization on maize productivity in strongly acid soils with liming

Several studies have recommended balanced fertilization for increased and sustainable maize productivity in northern Ghana. However, the effectiveness of balanced fertilization in strongly acid soils is unknown. We conducted nutrient omission trials on strongly acid soils in four communities in northern Ghana to quantify impact of balanced fertilization and its synergism with liming on maize productivity. We evaluated the following treatments, each with and without liming: (i) balanced fertilization (BF), which contained all essential limiting nutrients, (ii) BF without sulfur (minus-S), (iii) BF without zinc (minus-Zn), (iv) BF without boron (minus-B), (v) NPK-only, and (vi) control. Without liming, maize yield was generally low (ranging from 0.4 to 2.2 t ha−1) and followed the order: minus-Zn > NPK-only > BF = Minus-S = Minus-B > Control. However, regardless of fertilization treatment, liming significantly increased maize productivity with grain yields ranging from 0.7 to 4.2 t ha−1, with BF having the greatest yield. With liming, the minus-Zn treatment resulted in a ≥ 30% yield decrease, compared to BF. The combined data suggest that in strongly acid soils, unless lime is applied, addition of micronutrients to NPK fertilizers would not have the desired effect on maize productivity. Without lime application to such soils, omission of Zn from BF in will not only reduce production cost but could have a positive impact on maize productivity. However, we recommend that BF in strongly acid soils should be accompanied by liming to ensure increased and sustainable productivity.

Managing essential plant nutrients to improve maize productivity in the savanna agroecological zones of Northern Ghana: the role of secondary and micronutrients

Studies have shown that despite the positive response of maize to nitrogen (N), phosphorus (P), and potassium (K), actual yields in the savanna agroecological zones (AEZs) of northern Ghana remain well below the potential even with N-P-K fertilizer application. In a two-year nutrient omission trial in 12 locations within the Sudan savanna and Guinea savanna AEZs of northern Ghana, we quantified maize yield increases resulting from addition of secondary and micronutrients from the NPK-only fertilization practice for maize production in the two AEZs. In both years, applying only NPK fertilizer resulted in average yields of 3.6 t ha − 1 and 2.5 t ha − 1 in the Guinea savanna and Sudan savanna AEZs, respectively. However, addition of sulfur (S), zinc (Zn), and boron (B) to the NPK fertilizers (“balanced” fertilization) resulted in an average of 60% and 64% yield increases over those of the NPK-only treatment in the Sudan savanna and Guinea savanna AEZs, respectively. Compared to balanced fertilization, omission of S, Zn, and B reduced grain yield by an average of ∼34%, ∼28%, and ∼14%, respectively. The combined data suggest that, even though secondary- and micronutrients are needed in small quantities by plants relative to N, P, and K, they have an enormous effect on crop productivity. Therefore, to ensure sustainably increased maize productivity in the savanna agroecological zones of northern Ghana, fertilizer recommendations should not be restricted to only NPK fertilizers but all limiting secondary- and micronutrients must be accounted for in a holistic and balanced fertilizer recommendation.