Imbalanced application of nitrogen(N) and phosphorus(P) fertilizers can result in reduced crop yield,low nutrient use efficiency,and high loss of nutrients and soil nitrate nitrogen(NO_3^--N) accumulation decreases when N is applied with P and/or manure;however,the effect of applications of N with P and/or manure on root growth and distribution in the soil profile is not fully understood.The aim of this study was to investigate the combined effects of different N and P fertilizer application rates with or without manure on maize(Zea mays L.) yield,N uptake,root growth,apparent N surplus,Olsen-P concentration,and mineral N(N_(min)) accumulation in a fluvo-aquic calcareous soil from a long-term(28-year) experiment.The experiment comprised twelve combinations of chemical N and P fertilizers,either with or without chicken manure,as treatments in four replicates.The yield of maize grain was 82%higher,the N uptake 100%higher,and the N_(min) accumulation 39%lower in the treatments with combined N and P in comparison to N fertilizer only.The maize root length density in the 30-60 cm layer was three times greater in the treatments with N and P fertilizers than with N fertilizer only.Manure addition increased maize yield by 50%and N uptake by 43%,and reduced N_(min)(mostly NO_3^--N) accumulation in the soil by 46%.The long-term application of manure and P fertilizer resulted in significant increases in soil Olsen-P concentration when no N fertilizer was applied.Manure application reduced the apparent N surplus for all treatments.These results suggest that combined N and P fertilizer applications could enhance maize grain yield and nutrient uptake via stimulating root growth,leading to reduced accumulation of potentially leachable NO_3^--N in soil,and manure application was a practical way to improve degraded soils in China and the rest of the world.
Overuse of fertilizers and the resultant pollution and eutrophication of surface and groundwater is a growing issue in China. Consequently, improved management strategies are needed to optimize crop production with reduced nutrient inputs. Conventional fertilization （CF）, reduced fertilization （RF）, and reduced fertilization with maize （Zea mays L.） as a summer catch crop （RF＋C） treatments were evaluated in 2008 and 2009 by quantifying tomato （Lycopersieon esculentum） fruit yield and soil nutrient balance in a greenhouse tomato double-cropping system. Fertilizer nitrogen （N） application was reduced by 37% in the RF and RF＋C treatments compared to the CF treatment with no significant reduction in fruit yield. Mean soil mineral N （Nmin） content to a depth of 180 cm following tomato and maize harvest was lower in the RF and RF＋C treatments than in the CF treatment. Residual soil Nmin content was reduced by 21% and 55% in the RF and RF＋C treatments, respectively, compared to the CF treatment. Surplus phosphorus （P） and potassium （K） contents in the RFWC treatment were significantly lower than those in the RF treatment, mainly due to additional P and K uptake by the catch crop. We concluded that for intensive greenhouse production systems, the RF and RF＋C treatments could maintain tomato fruit yield, reduce the potential for nitrate （NO3^--N） leaching, and with a catch crop, provide additional benefits through increased biomass production.
