Information is needed on the long-term impact of cropping system and N fertilization on dryland soil health and crop yields. We studied the 13-yr effect of cropping system and N fertilization rate on soil chemical properties at the 0-to 60-cm depth and related them to annualized crop yield in the northern Great Plains. Cropping systems were conventional tillage barley (Hordeum vulgare L.)/spring wheat (Triticum aestivum L)-fallow (CTB/WF), no-tillage barley/spring wheat-fallow (NTB/WF), notillage barley/spring wheat-pea (Pisum sativum L) (NTB/WP), and no-tillage continuous barley/spring wheat (NTCB/W). Nitrogen fertilization rates were 0, 40, 80, and 120 kg N ha −1 to barley planted from 2006 to 2011 and 0, 50, 100, and 150 kg N ha −1 to spring wheat planted from 2012 to 2018. At 0 to 5 cm, soil pH and CEC were greater with NTB/WP than NTCB/W and CTB/WF, and soil organic matter (SOM) and Olsen-P were greater with NTCB/W than CTB/WF. Increased N rate reduced soil pH, K, Ca, Mg, and CEC at most soil depths. Annualized crop yield was greater with NTCB/W and NTB/WP than NTB/WF and CTB/WF and maximized at 80-100 kg N ha −1. Most soil chemical properties induced by N fertilization were negatively correlated, but Mg concentration at 30-60 cm induced by cropping system was positively correlated with annualized crop yield. No-till barley/spring wheat-pea rotation with 80-100 kg N ha −1 can sustain dryland soil chemical properties and barley and spring wheat yields in the northern Great Plains. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

This research was carried out to determine the best phosphorus fertilizer for improvement of sweet potato phosphorus uptake, growth and yield. The phosphorus fertilizer sources used were organic (Pacesetter), single super phosphate and crystallizer while the sweet potato variety used was Shaba. The experiment was laid out in randomized complete block design (RCBD) with three replications. Sweet potato plants from plots treated with crystallizer fertilizer at the rate of 500kg/ha had the highest phosphorus uptake and vegetative growth while control plots produced plants with highest tuberous yield. It is, therefore, recommended that crystallizer applied at the rate of 500kg/ha be used for significant phosphorous uptake which equally leads to better quality sweet potato tuber and appreciable vegetative growth. It is also recommended that the soil phosphorus be maintained at low level around 6.80mg/kg for achievement of high tuberous yield in sweet potato.

The objective of this study was to evaluate the yield and quality of sweet potato under the influence inorganic fertilizer (NPK 15:15:15) at the recommended rate of 130kg/ha, organic fertilizer (Pace Setter) at the recommended rate of 3t/ha and organo-mineral fertilizer (combination of NPK 15:15:15 and Pacesetter organic fertilizer) at the rate of 1.5 t/ha. The fresh and dry weights of the samples were taken after which their proximate analyses were done to determine the levels of the quality determinants (moisture content, crude protein, ether extract, crude fibre, Vitamin A and ash content) in them. At the end of the experiment, harvesting was done to determine the yield per treatments as well as the quality parameters of the leaves and tubers. It was found that organic fertilizer could increase the quantity of ether extract, crude fibre and vitamin A contents of sweet potato tubers above other fertilizer treatments though organic fertilizer competed with the control in increasing the ash and crude protein contents of sweet potato tubers. However, inorganic fertilizer increased only energy content of the tubers above organic and organo-mineral fertilizer treatments. It is, therefore, concluded that organic fertilizer should be used to increase sweet potato tuber quantity and quality.

Biochar is a chemically recalcitrant carbon-rich solid material used in soil for its potential to improve soil quality and sequester carbon. While the rate of application has implications for soil carbon dioxide (CO 2) emission and the overall benefits of biochar, its effects are yet to be fully understood. To evaluate the effect of application rates of rice husk biochar on CO 2 emissions, 91-day field experiments were conducted on three soil types (Anthraquic Ustorthent, Grossarenic Kandiustalf, and Ustic Quartzipsamment) in the southern Guinea Savannah of Nigeria, using three biochar application rates of 5, 15 and 25 t h À1 , and control. A two-way ANOVA showed that cumulative CO 2 emissions were significantly (p < 0.01) different between soil types and treatments, and soil type/treatment interactions were also significant at p ¼ 0.05. The highest cumulative CO 2-C emission of 2.77g/m 2 was recorded in the Grossarenic Kandiustalf, while the least value of 2.11g/m 2 was recorded in the Ustic Quartzipsamment. CO 2 emission increased with increasing biochar application rates, with the highest (3.06 CO 2-C g/m 2) value recorded at 25 t/ha compared to 2.78 g/m 2 and 1.52 g/m 2 values recorded for 5 t/ha and control treatments respectively. While CO 2 emissions increased with biochar application rate however, the percentage of biochar-C mineralized was higher at lower biochar rates, and differences were significant at p ¼ 0.01. While 0.63 % of biochar C was mineralized under 5 t/ha biochar treatment, 0.15 % was recorded for 25 t/ha treatment. Factors that had significant correlation with CO 2-C emission in the soils were biochar addition rate, soil pH, N, P, Ca, Mg and K. At day 91, there were no significant differences in CO 2 emissions between amended treatments and control, and only a small percentage (<1) of biochar C had been mineralized.

Having substantial and working knowledge on phosphorus fertilization is a pre-requisite to profitable tomato production. Thus, the present research was conducted to determine the optimum phosphorus (P) fertilizer rate for better fruit yield of tomato in Ilorin, a location in the Southern Guinea savannah zone of Nigeria. Five levels of phosphorus (0, 30, 60, 90 and120kgP/ha) were tested on UC82B tomato variety. The experiment waslaid out in a randomized complete block design with 3 replications. Data were collected on plant height, number of leaves, leaf area and number of branches at different growth stages while data on fruit yield as well as its components were collected at harvest. Results showed that application of 30kgP/ha produced plants with the highest leaf area. The control and 30kgP/ha produced the highest number of leaves. Application of 90kgP/ha and 120kgP/ha resulted in production of highest number of fruits while application of 90kgP/ha alone resulted in production of the tallest plants, highest number of branches and highest fruit yield. The yield was 66% better than the control. It was, therefore, concluded that 90kgP/ha should be used for optimum tomato fruit production in the agro-ecological zone of the research and places with the same climatic and edaphic conditions. Keywords: Phosphorus fertilization, tomato, growth improvement and fruit yield

This study assessed growth and yield performances of maize under the influence of inorganic fertilizer, population density and variety using the following treatments: maize varieties DMR-ESR-Y and Suwan- 1-SR; 70 × 30cm and 100 × 40cm plant spacing; 0, 60 and 120 kg NPK/ha . Data were collected on number of leaves per plant, plant height, ear height, leaf area, leaf area index, days to 50% flowering, days to tassel and silk appearances, stem dry mass, root dry mass, cob mass, number of kernel rows, number of kernels per cob, harvest index, treatment yield per hectare. The result showed that combination of 120kgN/ha, DMR-ESR-Y and 47, 619 plants/ha improved root, shoot, leaf sheath and plant dry masses, cob length, cob diameter, shelling percentage, moisture content at harvest, harvest index, number of cobs per plant as well as number of kernels per row. It is, therefore, recommended that combination of 120kgNPK/ha, DMR-ESR-Y and 47,619 plants/ha should be used for better maize production to cater for the ever increasing population of consumers in Southern Guinea savannah agroecological zone of Nigeria and other area with the same climatic and edaphic conditions. Keywords: NPK fertilizer, population density, maize variety, yield improvement

To guard against soil phosphorus (P) toxicity in tuber production and have optimum tuber yield at lesser cost of P-fertilization, better understanding of the dynamics of phosphorus release in sandy loamy soil is inevitable. Therefore, this work was carried out to investigate the trend of P-release from time of application to its optimum release and its effect on sweet potato growth and tuber production. To achieve this, a 5-week incubation study under laboratory conditions was carried out to study P-release dynamics using different P sources. Similar experiment was conducted on the field using the same P sources and application rate to monitor the influence P-release rate on sweet potato production. Data on number of leaves, vine length, tuber yield, soil extractable phosphorus and phosphorus uptake of the plants were taken. Relationships between P-uptake and tuber yield, number of leaves, vine length were also established. It was found that the trend of phosphorus release was a sigmoid shape. Leaf production and vine length were improved by P-application, while yield was suppressed. It is recommended that P-fertilizer should not be applied to the soil at short intervals to avoid nutrient toxicity.