Agronomy for Sustainable Development

Wet olive pomace is an organic lignocellulosic material, a by-product of the olive milling process, a typical and traditional activity in many Mediterranean countries. Wet olive pomace has difficult commercialization due to its high moisture content of 55–65%, that causes a noticeable increase in oil extraction costs. However, it could be conveniently reused in agriculture as a valid soil amendment to improve soil fertility and structure. Here, we studied the effects of the application of increasing amounts of non-fermented wet pomace on the fertility of a silty-clay soil, grown with 3 crops in succession: sunflower-wheat-wheat. The experiments were conducted at the Agricultural Faculty of Bari, Italy, on a Pachic Hoploxeroll soil characterized by illite and kaolinite and large amounts of Fe and Al sesquioxides. We compared the effect of wet pomace applied at amounts ranging from 0 to 210 Mg ha−1, incorporated 60 days prior to sunflower sowing. In the wheat late season of the second year, average samples from the 0–0.60 m layer were taken and tested for structural stability, organic matter, total nitrogen, available phosphorus, exchangeable potassium, pH and saturation extract electrical conductivity. The results indicate that the application of wet pomace induces a general improvement in soil fertility. In particular, the incorporation of increasing amounts of wet pomace improved nutrient content. For instance, an application of 210 Mg ha−1 of wet pomace increased soil organic matter by +84%, total N by +0.90 g kg−1, available P by +79.40 mg kg−1 and exchangeable K by +80 mg kg−1. We also observed an improvement in soil structure, which is of particular importance in hot, arid environments and in sustainable agricultural systems.

The physical, chemical and biological properties of soil may be modified by tillage, fertilization and cover crops. However there is little knowledge on long-term effects on soil properties, notably under Mediterranean climate. Moreover, biological indicators such as micro-arthropods can be used for a cost-effective analysis of soil biodiversity. Here, we studied physical and biological properties of a sandy loam soil in central Italy under a 4-year rotation of maize–durum wheat–cover crop–sunflower–durum wheat–cover crop during 15 years. We analysed the effects of two tillage systems, conventional tillage (CT) and no-tillage (NT); two N fertilization rates, without N and medium N level; and three soil covers: cash crop residue as control, Brassica juncea and Vicia villosa. Results show that no tillage increased soil organic matter content in the upper 10-cm layer (3.31%) compared to the conventional tillage (2.19%). No tillage also improved structure stability and lowered bulk density in the same soil profile. No-tillage systems showed higher soil microbial biomass (+71%) and respiration (+44%), and a higher abundance and diversity of micro-arthropods. We conclude that no tillage is an effective measure to improve the physical and biological quality of soil in Mediterranean conditions. No-tillage positive effect can be enhanced by the right choice of N fertilization and cover crop cultivation. Bio-indicators such as micro-arthropods can be very predictive of soil habitability by organisms.

Recent European incentive policies clearly targeted decreasing pesticide use in all agricultural systems as a key option to reduce environmental hazards and health risks. To reduce pesticide use is challenging in orchards where pesticides are recurrently applied to control numerous pests and diseases, but crucial to improve fruit production sustainability. Agricultural research has provided alternatives to chemical control for the management of a single pest or disease, but has very seldom addressed the design of overall sustainable strategies aiming at reducing pesticide use. New insights permitted by system approaches are now developing. Here, we report the level of pesticide use and the agri-environmental performances of three protection systems of apple orchards surveyed from 2005 to 2008: (1) conventional, (2) low-input and (3) organic farming. To assess the significance of the cultivar in decreasing pesticide use, these protection systems were combined with three cultivars differing in scab susceptibility: ‘Ariane’ (Vf-resistant), ‘Melrose’ (low-susceptibility) and ‘Golden Delicious’ (susceptible). Thus, nine ‘management × cultivar’ apple orchard systems were assessed. The level of pesticide use was the highest in conventional ‘Golden Delicious’ and in ‘Golden Delicious’ plots whatever the protection system. A 43–56% decrease in pesticide use was observed in ‘Ariane’ and ‘Melrose’ in both low-input and organic farming protection systems compared to conventional ‘Golden Delicious’ as reference. Only low-input ‘Melrose’ and low-input ‘Ariane’ systems achieved a level of yield and fruit damages similar to the corresponding conventional cultivars under reduced pesticide use, also permitting reduced environmental impacts. But even the low-input ‘Melrose’ least pesticide-dependant system was far from being pesticide-free, suggesting that current straight-designed mono-clone orchards are hardly appropriate to drastically reduce pesticide use and that the range of commercial apple cultivars should be renewed to offer more robust cultivars.

Despite efforts to increase agricultural production sustainably in sub-Saharan Africa, large gaps remain between actual and potential yield of food crops. Adding biochar to degraded cropland soils in the African tropics has significant potential to enhance crop productivity. Biochar-based farming can also mitigate climate change, through soil carbon storage. This study involved six smallholder farms at sites in eastern, central, and western Kenya that are characterized by different pedo-climatic conditions. We examined the response of non-fertilized and fertilized maize monoculture to three dosages of biochar that are realistic for domestic production by farmers at each of the sites over four growing seasons. Commonly available biomass wastes in each agro-ecosystem (coconut shells, coffee husks, maize cobs) were used as feedstock for biochar, which was applied at 1, 5, and 10 Mg ha−1 at the start of the experiment. Across seasons and fertilizer treatments, maize grain yield (dry matter) showed consistently positive responses, with an average increase of 1.0, 2.6, and 4.0 Mg ha−1, respectively, above the control for the three biochar application rates. Absolute responses of maize grain yield to specific biochar doses were similar across the four investigated seasons and replicate farms within sites, and uncorrelated to yield levels in the control treatment. Here, we show for the first time that yield response to biochar decreased with increasing application rate, indicating that it may be better to spread a given amount of biochar over a large area rather than concentrating it to a smaller area, at least when biochar is applied along plant rows at rates ≥1 Mg ha−1, as in our experiment. This study demonstrated that application of biochar, locally produced from available biomass residues, is a promising approach to enhance agricultural production and carbon storage on smallholder farms under a wide range of pedo-climatic conditions in Kenya.

Stubble grazing by livestock in post-harvest wheat fields is a common practice. Current knowledge usually shows that grazing has negative effects on soil quality. Therefore, here, we studied the stubble grazing impact on soil quality and crop yields of continuous wheat croplands in the semi-arid northern Negev of Israel. These croplands have experienced the same stubble residue management, meaning, moderate grazing or entire retention, for 18 consecutive years. Cropland soils were also compared with soils of natural lands. Vegetation and 0–10 cm depth soils were sampled in 2013. Results reveal that overall soil quality was generally similar between the two wheat treatments. Moreover, results show that soil under stubble grazing treatment has greater carbon pool index and carbon management index than soil under stubble retention treatment. These findings suggest that the disturbance of soil organic carbon pool is smaller for stubble grazing, contrary to current knowledge. We propose a conceptual model to explain such findings.

Nhờ vào nhu cầu phân bón thấp và nhu cầu tiêu thụ cao, các giống lúa mì cổ đại và các giống lúa mì durum cổ đại đã trở thành một lựa chọn hấp dẫn cho các khu vực biên giới của môi trường Địa Trung Hải không còn được canh tác do sản lượng hạt thấp khi sử dụng các giống lúa mì hiện đại. Việc sử dụng kép có thể tăng giá trị của chúng trong các hệ thống trồng trọt này, nhưng không có thông tin nào về sự phù hợp của các loài lúa mì cổ đại đối với loại hình sử dụng này. Để lấp đầy khoảng trống này, lúa mì Khorasan, einkorn và emmer đã được so sánh trong một thử nghiệm thực địa kéo dài hai năm, với các cây được cắt ở giai đoạn hoa chóp hoặc không cắt. Hạt được gieo vào tháng 10, tại Sardinia (41°B, 80 m asl), Ý, trên đất có độ màu mỡ thấp và với tỷ lệ phân bón thấp đến trung bình. Các giống einkorn đã tạo ra năng suất sinh khối cao nhất (2–3 t ha−1), phản ánh thời gian dài hơn để bắt đầu giai đoạn hoa chóp (119–138 ngày). Sau khi cắt, tất cả các loài đã phục hồi khả năng tiếp nhận bức xạ đạt đến mức của các vụ mùa không cắt, nhưng việc cắt làm giảm hiệu suất sử dụng bức xạ của chúng. Năng suất hạt không bị ảnh hưởng bởi việc cắt: sự gia tăng chỉ số thu hoạch đã bù đắp cho sự giảm sút trong sinh khối. Chúng tôi cho thấy lần đầu tiên rằng các loài lúa mì cổ đại phù hợp với việc sử dụng kép (cỏ và hạt trong cùng một mùa), điều này làm cho chúng có giá trị cho các khu vực biên giới; lý do là việc gieo trồng sớm được áp dụng cho sử dụng kép cho phép chúng tận dụng tối đa thời gian trễ của mình về năng suất cỏ và làm cho việc nở hoa diễn ra sớm hơn (tức là sớm hơn), do đó mà đạt được năng suất hạt thỏa đáng, ngay cả dưới áp lực nước nghiêm trọng. Việc sử dụng kép của lúa mì cổ đại làm tăng tính bền vững của các hệ thống trồng trọt hỗn hợp, bằng cách cung cấp cỏ cho động vật trong một giai đoạn quyết định, mà không làm giảm sản lượng hạt đạt được sau chăn thả trong cùng một mùa.