Mechanized crop production schemes continue to be the main source of grain sorghum in the Sudan, where fertilizer experiments have shown that applications of NP and NPK significantly increase the grain yield of continuous sorghum, though economic increases could be obtained by the application of nitrogen.

N-enriched biochar can increase the accumulation of carbon (C), nitrogen (N), phosphorus (P), and biomass in rice plants. On the other hand, the biomass and C, N, and P contents of plant organs are important indicators to reflect plant C, N, and P storages. We established control, 4 t ha−1, and 8 t ha−1 N-enriched biochar treatment plots in a subtropical paddy field in China to investigate the effect of these treatments on C, N, and P storages, ecological stoichiometry in various rice plant organs, and their relationships with edaphic factors. The application of N-enriched biochar increased the biomass and storages of C, N, and P in rice roots, stems, leaves, and grains, mainly at 4 t ha−1. The application of N-enriched biochar decreased the C/N and C/P ratios of rice organs, but increased their N/P ratio. Changes in C/N were mainly due to the changes in storage, while N/P was positively correlated with N storage of stems, leaves, and grains and negatively correlated with P storage in roots. Pearson’s correlation analysis revealed that pH was negatively correlated, and soil N content was positively correlated with P storage in various organs of rice. In addition, soil P content and chlorophyll were positively correlated with N storage. In conclusion, we found that the application of N-enriched biochar improved plant N and P storage and stoichiometrical relations among rice organs.

Ethiopia has heterogeneous topographic, climatic and socio-ecological systems. Recommendations of agricultural inputs and management practices based on coarse domains such as agro-ecological zones (AEZ) may not lead to accurate targeting, mainly due to large intra-zone variations. The lack of well-targeted recommendations may contribute to the underperformance of promising technologies. Therefore, there is a need to define units where similar environmental and biophysical features prevail, based on which specific recommendations can be made for similar response units (SRUs). We used unsupervised machine learning algorithms to identify areas of high similarity or homogeneous zones called ‘SRUs’ that can guide the targeting of agricultural technologies. SRUs are landscape entities defined by integrating relevant environmental covariates with the intention to identify areas of similar responses. Using environmental spatial data layers such as edaphic and ecological variables for delineation of the SRUs, we applied K- and X-means clustering techniques to generate various granular levels of zonation and define areas of high similarity. The results of the clustering were validated through expert consultation and by comparison with an existing operational AEZ map of Ethiopia. We also augmented validation of the heterogeneity of the SRUs by using field-based crop response to fertiliser application experimental data. The expert consultation highlighted that the SRUs can provide improved clustering of areas of high similarity for targeting interventions. Comparison with the AEZ map indicated that SRUs with the same number of AEZ units captured heterogeneity better with less within-cluster variability of the former. In addition, SRUs show lower within-cluster variability to optimal crop response to fertiliser application compared with AEZs with the same number of classes. This implies that the SRUs can be used for refined agricultural input and technology targeting. The work in this study also developed an operational framework that users can deploy to fetch data from the cloud and generate SRUs for their areas of interest.

Confidence limits of expected twenty-day rainfall have been computed for two widely separated maize-producing regions in Kenya. The 35-km. square survey areas were quite different topographically, and limits were derived for seven rainfall sites in each. Ratios of these limits to the corresponding long-term mean precipitations were evaluated for each site for each twenty-day period during the appropriate maize-growing seasons. For a particular period and confidence level, these ratios were almost constant for either group of seven sites. The variability computed for a single, well-chosen site is therefore representative of quite a large neighbourhood. Expected rainfall totals were also derived for a ‘fictitious’ site, simulating the average precipitation over the whole of the flatter of the two areas. The resulting limits were less extreme than those of any individual site, indicating that areal rainfall, as used in hydrology, is less variable than the agriculturally-important point rainfall.

Effects are reported of some factors which may influence emergence and establishment of pigeon pea (Cajanus cajan (L.) Millsp.), including seeding depth, seed dressing, seed grading, seeding rate, variety and temperature. The effect of seeding rate was dependent on mean germination percentage in the field, but circumstantial observations on other factors of possible consequence in determining plant stand are also discussed.

Substantial improvement is reported in a quality measure, large seed size, after only one generation of mass selection from a bulk ‘Chalimbana’ population of Zambian land races of the inbred species Arachis hypogaea L. There were large positive correlations between seed size as planted and the subsequent mean size harvested. Large seed also tended to produce an increased proportion of 2- rather than 3-seeded pods, further improving both crop uniformity and quality. Total yield was unaffected, or possibly even slightly enhanced, by planting larger kernels. The circumstantial advantages of mass as opposed to pedigree selection methods are discussed.

A series of N × P field experiments with irrigated rice, conducted over the period 1958–1962 on the same plots on alluvial soils considered representative for most of the bottom ‘fadama’ land in Niger and Ilorin Provinces, Northern Nigeria, showed small increases with medium dressings of P2O5 and large responses with high dressings of N. The N responses showed considerable variation between soil types and years. The variation between soil types was attributed to different cation exchange capacities, which resulted in NH4′ leaching from the root zone at different rates. The variation in N responses between years was probably due to different physiological timings of the top dressings. Results of chemical analyses of straw and grain samples of the 1961 crop were used to estimate the percentage of N and P2O5 recovered by the crop with the various treatments over the untreated plots in the previous years of the experiments on two soil types. The recovery percentages for the different levels of N on the clay ‘basin’ soils were moderate, about 18 per cent, whereas those for the sandy ‘levee’ soils were lower, averaging only 9 per cent. Recovery of P2O5 varied from good at medium N levels (14 per cent) to moderate at high N levels (9 per cent) on the basin soils. Recovery of P2O5 on the levee soils was poor. The utilisation of the recovered N (75 lb paddy/lb N) and P2O5 (42 lb paddy/lb P2O5) was very good for N and fair for P2O5.

Trials were carried out to ascertain which of four systemic insecticide/nematicides were absorbed by young coconut palms (Cocos nucifera L.) using three different methods of application. Stem injection of Bidrin and Nemacur are impractical because the chemicals break down too quickly and frequent retreatment would result in too much physical damage to the young trees. Lannate was not absorbed from leaf axil placement, and broke down too quickly when absorbed from the soil to be of practical use. Nemacur was not absorbed through the leaf axil, but was from the soil and lasted up to 14 weeks in the plant. Temik, absorbed both through the leaf axil and from the soil, lasted up to 14 weeks. The possibility of controlling red ring disease of coconuts with Nemacur or Temik is considered.