The production of maize in every second inter-row of first and second ratoon sugar cane was studied in four locations in Mauritius in 1974, in trials based on combinations of three maize densities and three fertilizer levels. Analysis of the data showed that intercropping sugar cane with maize had no adverse effects on cane and sugar yields, and suggested that planting an early-maturing maize amongst the cane at a density of 19,000 plants, with 76 kg N, 38 kg P2O5, 62 kg K2O/ha, was the most profitable method under Mauritian conditions.

Agricultural production on the Mahafaly Plateau in SW-Madagascar has traditionally been based on subsistence rain-fed agriculture, with yields declining as a result of low soil fertility, recurrent droughts, and erratic rainfall. Market-oriented vegetable production in this area may help households improve their nutrition and diversify their income. In field trials between the 2013 and 2016 dry cropping seasons, the feasibility of carrot (Daucus carota L.) and onion (Allium cepa L.) production was assessed by testing effects of manure and charcoal amendments, shading, and seed quality on yields. Due to damage caused by cyclones and strong winds, only data from 2013 and 2016 are reported in this paper. Additionally to the field experiments, effects of salinity on seed germination were also examined under laboratory conditions and in the field. Carrot dry matter (DM) yields were 0.24 to 2.76 t·ha−1 while those of onion were 0.15 to 0.99 t·ha−1 DM. While the combination of manure and charcoal application had only minor effects on crop growth, manure alone increased carrot yield by 26% across years. After one cropping season, manure application reduced soil pH from 9.0 to 8.6 and increased soil Corg from 0.87 to 1.76%, N from 0.08 to 0.14%, and P from 10.6 to 15.1 mg·kg−1. Shading reduced carrot yields from 0.87 to 0.58 t·ha−1 DM in 2013 and from 1.87 to 0.85 t·ha−1 DM in 2016, but increased onion yield in 2013 from 0.24 to 0.62 t·ha−1 DM. Carrot seed procured locally performed better in the field than seed imported from the capital which translated into differences in seedling emergence. Saline irrigation water (electrical conductivity = 7.03 mS·cm−1) reduced seedling emergence rate of carrot from 73 to 20% and for onion from 44 to 28% and unprimed seeds performed better than primed ones. Using shading during the dry season is not advisable for carrot and onion production, but improving seed quality and targeted use of soil amendments (time of manure application, manure quality) may enhance vegetable yields.

Sucrose yield in sugarcane is a complex process regulated by both environmental and endogenous factors. However, the metabolic balance driving vegetative growth and sucrose accumulation remains poorly understood. Herein, we carried out a comprehensive assessment of carbohydrate dynamics throughout the crop cycle in two sugarcane varieties varying in biomass production, evaluating the carbon metabolism in both leaves and stalks. Our data revealed that the decline in photosynthetic rates during sugarcane maturation is associated not only to accumulation of sugars in leaves but also due to stomatal and non-stomatal limitations. We found that metabolic processes in leaves and stalks were intrinsically linked. While IACSP94-2094 had higher stalk sucrose concentration than IACSP95-5000, this latter produced more biomass. Compared to IACSP95-5000, IACSP94-2094 showed higher sucrose phosphate synthase (SPS) activity in leaves and stalks, along with lower soluble acid invertase (SAI) activity in leaves during the maximum growth stage. Interestingly, IACSP94-2094 also exhibited higher stalk SPS activity and lower stalk SAI activity than IACSP95-5000 during maturation. High biomass production by IACSP95-5000 was associated with higher sucrose synthase (SuSy) and SAI activity in leaves and higher SuSy and soluble neutral invertase (SNI) activity in stalks when compared to IACSP94-2094 during the maximum growth. Despite the contrasting strategies, both varieties displayed similar total sucrose yield, a balance between sucrose concentration and biomass production. This phenomenon implies the presence of a compensatory mechanism in sugarcane, with high biomass production compensating low sucrose accumulation and vice versa.

Water deficiency is one of the most severe abiotic stresses in rainfed dry lands and limits crop productivity. Exogenous applications of salicylic acid (SA) have been applied to mitigate the adverse effects of water-deficit stresses, but the relative efficacy of different derivatives of SA in enhancing water-deficit tolerance along with the underlying physio-biochemical mechanism and yield of crops is not well documented. Field experiments were conducted to ascertain the relative efficacy of exogenous application of three plant bioregulators (PBRs) [SA, thiosalicylic acid and 5-sulfosalicylic acid (SSA)], each at three concentrations (0.5, 1.0 and 1.5 mM), on the growth, physio-biochemical characteristics and yield of cluster bean under rainfed conditions. Based on a 2-year field experiment, the application of PBRs enhanced yield (from 8 to 16%). The yield enhancement with the application of PBRs was associated with elevated water content (from 9 to 17%), membrane stability (from 12 to 18%) and antioxidant enzyme activity (from 12 to 33%) and reduced lipid peroxidation (from −15 to −34%) in leaves. The effects of PBRs were conditionally type and concentration dependent. The application of SSA at a rate of 1 mM was more effective in enhancing water-deficit tolerance and improving the yield of cluster bean under water shortage conditions. This study provides empirical evidence of the potential for the application of SA and its derivatives to enhance crop yields under drought conditions. The results have direct implications for sustainable crop production for similar regions of the world facing water deficits.

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.

In researcher-designed, farmer-managed experiments with cabbage and hot pepper, ground seashells (GSS) were compared with low-grade phosphate lime (LGP) at rates of 0, 2.5, 5, 7.5 or 10 t ha−1. A randomized complete block design, with replicates spread over different farms, was used. Liming with GSS or LGP at 10 t ha−1 increased cabbage yield from 0.5 t ha−1 without liming to 15.0 and 5.3 t ha−1 respectively. Hot pepper yield was increased from 2.1 t ha−1 without liming to 3.2 t ha−1 at the three highest rates of GSS and LGP. Application of GSS increased the pH, reduced exchangeable acidity and increased the extractable Ca content of the soil. Partial budget analyses revealed that cabbage and pepper growers obtained highest returns with GSS at 10 and 5 t ha−1 respectively.

Banana packing systems rely on floating the fruit in water in order to remove latex produced at the cut surfaces of the crown. At some periods of the year up to 5% of the fruit sinks and rolls along the bottom of the tanks, resulting in heavy scarring of the peel. Potassium content of buoyant fruit exceeded 1·3% dry weight in the pulp and 6·0% in the peel, but in one investigation the sinker fruit had 36 and 20% less than these levels respectively. Application of potassium fertilizer in the field greatly reduced the amount of sinker fruit.

A long-term field trial was conducted to determine yield trends in relation to nutrient uptake and efficiency in different rice-based cropping systems. The cropping systems had a significant effect on wet season rice yield when residues were not recycled but had no effect otherwise. Rice yield decreased after the first year of crop residue incorporation but increased every year thereafter. Rice yield was significantly affected by residual nutrients applied to dry season crops. The highest residual effect was observed in tomato and sweet pepper to which the highest nitrogen (N), phosphorus (P) and potassium (K) rates were applied. Maize, sweet pepper, and tomato responded well to NPK application, garlic had a low response and mungbean had no response. A relay crop served as a catch crop for excess nutrients and as shade to minimize sunscald effects for tomato and sweet pepper fruits.

The change in seed oil percentage and 100-seed weight of Brassica juncea Varuna was studied as the crop matured during rabi 1977–78. Statistically, the oil percentage reached its highest value at 55 days from flowering, whereas the 100-seed weight was highest about 20 days later, when the pods were fully yellow. Oil yield (the product of oil percentage and seed weight) also reached its highest value when the pods were fully yellow. This information should enable the crop to be harvested at the proper physiological stage (yellow-podded) for maximum oil yield.

A simple yet effective field screening technique for estimating drought tolerance is described. It involves growing plants in sloping plots which are opposite each other and connected to sub-channels lined with polyethylene sheet. The slopes are designed to achieve instant surface run-off and the sub-channels connected to a main channel for rapid drainage of rain-water. Stress is created at different stages of crop growth by manipulating the timing of irrigation and covering the soil surface with polyethylene sheeting. The technique proved effective even in the monsoon season which is characterized by irregular intensity and distribution of rainfall. Data on six characters for 80 genotypes of pearl millet grown in six artificially created environments representing different levels of moisture stress are discussed. The ‘slope’ technique was effective in creating different levels of moisture stress at various stages of crop growth and in distinguishing categories of genotypes by their relative drought tolerance.