Liming (L) is a common practice to mitigate soil acidification and enhance soil quality and crop productivity. However, in acidic soil, it is not clear how long-term application of lime and nitrogen (N)-based fertilizer affects soil chemical properties, the wheat and maize grain yields (GY), and N-use efficiency (NUE). Thus, to investigate the effects of N-based fertilizations without L (−L) and with L (+L) on wheat and maize GY and NUE through their effects on soil chemical properties, we analyzed a 28-year field experiment in acidic soil under a wheat-maize system in South China. The analysis was carried out between 1991 and 2010 (before L) and between 2011 and 2018 (after L). We categorized the treatments into (1) no fertilizer (C); nitrogen (N); N and phosphorus (NP); N and potassium (NK); N, P and K (NPK); and NPKC_R, NPK and crops residue (C_R) applications (NPKC_R), before L; and (2) C; N−L; N+L; NP−L; NP+L; NK−L; NK+L; NPK−L; NPK+L; NPKC_R−L and NPKC_R+L, after L. The effects of long-term fertilization resulted in lower soil pH by 15%, soil available K (AK) by 19%, P_Olsen by 6%, NO₃⁻-N by 15%, soil organic matter (SOM) by 16%, total N by 16%, and C:N ratio by 13% in −L soil than in +L soil. However, the accumulation of NH₄⁺-N was higher by 40% in −L soil than in +L soil. Wheat and maize GY, N recovery efficiency (RE_N), and N partial factor productivity (PEP_N) were more adversely affected by 8-year fertilizations in −L compared with fertilizations before L and in +L primarily because of the significantly decreased soil pH. Conversely, improvements in wheat and maize yields, RE_N, and PFP_N by 8-year fertilizations in +L were related to increasing soil pH, exchangeable base cations such as Ca²⁺, Mg²⁺, and the alleviated toxicity of Al³⁺. Overall, improvement of GY and NUE from the acidified soil in South China requires the long-term integrated use of fertilizer (NPK), retention of C_R, and the +L (i.e., NPKC_R+L).

The excessive use of chemical phosphorus (P) fertilizer can lower grain yield and P use efficiency (PUE) by aggravating soil acidity. Substituting organic manure for chemical fertilizer can alleviate the problem, although the long-term effect of organic manure incorporation is unknown. We conceptualized that substituting organic manure for chemical fertilizer may result in higher crop yields and PUE. Therefore, the impact of long-term fertilizer treatments: (i) CK (control), (ii) PK (phosphorus and potassium fertilizer), (iii) NP (nitrogen and P fertilizer), (iv) NK fertilizer, (v) NPK fertilizer, and (vi) NPKM (30% NPK fertilizer plus 70% manure) on rice yield, PUE, P uptake, and apparent balance (APB) was investigated. The results showed that rice yield under different fertilizer treatments ranged from 6.2 to 11.8 t ha⁻¹ (1984–1995), 7.9 to 12.7 t ha⁻¹ (1996–2007), and 6.6 to 12.8 t ha⁻¹ (2008–2018). The rice yield under NPKM was greatly improved compared to other treatments, except with that of NPK (1984–1995). Soil organic carbon (SOC), available P and phosphorus activation coefficient (PAC) under NPKM were significantly higher than other treatments during 1984–2018. Soil pH (1984–2018) was greatly higher under CK and NPKM than under other treatments. Soil total P under PK, NP, NPK, and NPKM was significantly higher than under CK and NK (1984–2018). Compared to other treatments, P uptake was significantly higher under NPKM, except with that of NPK (1984–1995 and 2008–2018). The average PUE (1984–2018) was 10.7, 20.2, 36.1, and 44.2 kg kg⁻¹ under PK, NP, NPK, and NPKM, respectively. The APB under NPKM was significantly lower as compared to PK, NP, and NPK treatments. Therefore, we conclude that in addition to improving soil organic carbon, cations inputs from organic manure can be a factor for the increase in soil pH, making organic manure substitution for chemical fertilizer a more efficient strategy for increasing PUE and crop yield.

The study was conducted in Eastern Ethiopia, namely Meta and Tullo districts, during the 2015 cropping season to determine the effect of N fertilizer levels on N uptake, N use efficiency (NUE) and grain yield on bread wheat cultivars. Factorial combinations of five N levels (0, 30, 60, 90, and 120 kg N ha-1) and four bread wheat cultivars (Danda’a, Digalu, Kakaba and local cultivar) were laid out as a randomized complete block design (RCBD) with three replications. The interactions of sites, N levels, and cultivars significantly (p ≤ 0.01) affected grain yield (GY), nitrogen uptake by grains, total nitrogen uptake, nitrogen uptake efficiency (NUpE) and nitrigen use efficiency for grain yield (NUEGY). Main effects of sites, N levels and cultivars had significant (p < 0.01) effect on grain and straw N contents, straw N uptake, N biomass production efficiency, N utilization efficiency (NUtE) and nitrogen harvest index (NHI). The cultivar Kakaba at rate of 90 kg N ha-1 produced the highest grain yield (4880 kg ha-1) in Tullo, which was statistically similar with the grain yield (4816 kg ha-1) obtained from the cultivar Digalu with 120 kg N ha-1 in Meta district. The NUEGY was higher with values of 24.2 and 24.1 kg grain kg-1 N in Tullo and Meta districts, respectively, for Digalu cultivar at 30 kg N ha-1 application rate than the remaining N levels and variety interactions at both sites. Cultivars variations in NUEGY under low N application levels were mainly due to higher variations in NUpE than in NUtE. Therefore, there is a need for exploration of the effectiveness of various combinations of N rates with time of applications for improvements of N-use efficiency traits and cost effectiveness in improved wheat cultivars production.

The experiment was conducted to assess the integrated effects of pre-emergence herbicides and hand-weeding on weed control, yield components, yield, and their economic feasibility for cost effective weed control in faba bean. The experiment consisted of 12 treatments viz. pre-emergence s-metolachlor (1.0, 1.5 and 2.0 kg ha-1) and pendimethalin (1.0, 1.25 and 1.5 kg ha-1), each at three rates metolachlor, s-metolachlor + one-hand-weeding, pendimethalin + one-hand-weeding, two-hand-weeding, complete weed free and weedy checks arranged. The weed flora consisted of broadleaved and sedge with the relative densities of 81.02 and 18.98 % at Haramaya district, and 80.83% and 19.17%, at Gurawa district, respectively. Application of s-metolachlor and pendimethalin 1.0 kg ha-1 each supplemented with hand weeding 5 WAE significantly (p ≤0.01) affected the broadleaved weeds, sedges and weed dry weight at both sites. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE gave the lowest total number of weeds (8.29 m-2) following the weed free check. Higher grain yield (3555.8 kg ha-1) was produced with s-metolachlor 1.0 kg ha-1 supplemented with one-hand-weeding 5 WAE following complete weed-free at Gurawa. The benefit gained from s-metolachlor and pendimethalin at 1.0 kg ha-1 each supplemented with one hand weeding 5 WAE were greater than the value recorded from the weedy check by 216% and 198 %, respectively. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE treatment resulted in the highest grain yield and economic benefit. However, in case labour is constraint and s-metolachlor herbicide is timely available, pre emergence application of s-metolachlor at 2.0 kg ha-1 should be the alternative to preclude the yield loss and to ensure maximum benefit.