Precision manure management is a relatively new concept that merges the best agronomic and manure management practices along with precision agricultural techniques, such as site-specific management zones (MZs), for agricultural productivity and environmental quality. The objective of the study was to assess the influence and compare the economic efficiency of variable-rate applications of animal manure on grain yield in maize (Zea mays L.) fields across MZs in limited irrigation cropping systems. The study was conducted on furrow-irrigated maize fields in northeastern Colorado, USA. Fields were classified into low, medium, and high yielding MZs, based on soil color, elevation, and yield history. Experimental strips were 4.5 m wide and 540 m long spanning across all MZs with manure and N fertilizer management strategies nested within MZs. Variable-rate manure applications of 22, 44, and 67 Mg ha -1 were considered for variable yield goal (VYG) and constant yield goal (CYG) manure management strategies. The results of this study indicates that maize grain yield was significantly different across MZs a majority of times, however, not always consistent with the MZ productivity level. For instance, the low MZ showed a significantly (P £ 0.05) higher grain yield under a CYG manure management strategy. The enterprise budget analysis indicated that application of animal manure alone was economically inefficient for maize grain production. The study suggests that variable-rates of manure can be used in conjunction with synthetic N fertilizer to ensure that crop N requirements are met at early growth stages of maize.

No abstract

Recovery of nutrients from biogas slurry (BGS) as a soil amendment, on low input smallholder farms in sub-Saharan Africa, could improve agricultural production and minimize contribution of the agroecosystems to CO 2 emissions. Comparative effects of BGS and cattle manure (CM) on maize dry matter, grain yield, uptake of nitrogen (N), phosphorus (P) and potassium (K), and soil total N, extractable P and exchangeable K after harvest were studied, relative to chemical fertiliser (CF). The field experiment was conducted in the 2016/2017 and 2017/2018 growing seasons and was arranged in a randomized complete block design replicated four times with (i) BGS, (ii) CM and (iii) CF as the treatments. Each treatment was applied at 40, 80 and 120 kg Nha À1 . Additional P was added to BGS and CM to have the same added P as in the CF treatments. The CM treatment had higher dry matter than both BGS and CF in both seasons at each N rate. Maize grain yield from CF treatment was higher than the two organic fertilisers at each N rate, while the BGS treatment had higher grain yield than CM except at 40 kg Nha À1 . When applied at the same N rate, BGS resulted in lower P and K than CF, and had higher extractable P with lower exchangeable K when compared with CM. The findings imply that while BGS provided nutrients, it resulted in lower maize dry matter than CM and lower grain yield than CF, but raised total N and available P, over time.

Abstract. Humanity depends on the existence of healthy soils, both for the production of food and for ensuring a healthy, biodiverse environment, among other functions. COVID-19 is threatening food availability in many places of the world due to the disruption of food chains, lack of workforce, closed borders and national lockdowns. As a consequence, more emphasis is being placed on local food production, which may lead to more intensive cultivation of vulnerable areas and to soil degradation. In order to increase the resilience of populations facing this pandemic and future global crises, transitioning to a paradigm that relies more heavily on local food production on soils that are carefully tended and protected through sustainable management is necessary. To reach this goal, the Intergovernmental Technical Panel on Soils (ITPS) of the Food and Agriculture Organization of the United Nations (FAO) recommends five active strategies: improved access to land, sound land use planning, sustainable soil management, enhanced research, and investments in education and extension. The soil is the great connector of lives, the source and destination of all. It is the healer and restorer and resurrector, by which disease passes into health, age into youth, death into life. Without proper care for it we can have no community, because without proper care for it we can have no life. – Wendell Berry (American novelist)

Maintenance and improvement of soil quality across spatially variable soils in continuous cropping systems are critical to sustaining agricultural productivity and environmental quality. The objectives of this project were (i) to study the effects of variable-rate application of animal manure on selected topsoil quality parameters across site-specific management zones (MZs) and (ii) to evaluate the variable-rate applications of manure using risk-assessment tools of nitrogen (N) leaching and phosphorus (P) runoff indices to understand its impact on environmental quality. This study was conducted in northeastern Colorado on continuous and furrow-irrigated maize fields. Experimental strips, 4.5 m wide and 540 m long, spanned across all MZs with treatments nested within MZs in the field. Variable rates of dairy and beef feedlot manure applied on irrigated and dryland fields respectively ranged from 0 to 67 Mg ha −1 . Surface soil quality parameters evaluated before and after this study included bulk density, organic matter, water-holding capacity, electrical conductivity, and particlesize analysis. Results indicate that animal manure applications of 44 and 67 Mg ha −1 significantly (P ≤ 0.05) increased soil organic matter and decreased bulk density of low-and medium-productivity-level MZs and had no significant impact on surface soil organic matter and bulk density of the high-productivity-level MZs. Animal manure significantly (P ≤ 0.05) increased surface soil water-holding capacity and soil electrical conductivity across zones; however, the maximum manure-induced soil EC was 1.0 dS m −1 , which was below levels regarded as potentially harmful for maize production. Soil texture was not affected by animal manure applications. Colorado N leaching and P index indicated no environmental hazard associated with variable rate application of animal manure across MZs. This study indicates that variable-rate application of animal manure across MZs has potential to improve or maintain soil quality parameters over time without impairing the environment.